Bicycle lighting
Encyclopedia
Bicycle lighting improves the visibility of the bicycle
rider to others in dark conditions, i.e. to increase the rider's conspicuity and to enhance the ability of the rider to see, illuminating the way forward. Both reflectors and active lights are used to make the rider more visible, and many jurisdictions require one or more types of light to be fitted to bikes ridden at night. White light in the front, red lights in the back, with orange reflectors on the side is the most common setup. Many types of light sources are used for bicycle lights.
The earliest bicycle and motor-car Carbide lamp
s were powered by acetylene gas, produced by combining calcium carbide
with water. The light given was very bright, although the lamps required regular maintenance; the arrival of battery-powered lamps in the 1890s was well received.
Early battery lamps generally used a lead-acid battery
, but these were replaced by self-contained dry cells
; lamps became smaller and more reliable. At the same time dynamo
s were developed which generated energy from the bicycle's own movement. These were more practical, as storage density in batteries was at this time very low.
Not all jurisdictions required use of lights after dark. In the UK the law requiring use of rear lights was resisted by cyclists' groups on the grounds that it downplayed motorists' obligation to be able to stop well within the distance they can see to be clear.
Replaceable-cell battery lights had a renaissance on the invention of the alkaline battery
, with a much higher storage density. Moulding techniques for plastics also improved, allowing lens
optics
to be refined at low cost thus making more efficient use of the light output. During the 1980s the lighting market became more globalised: in Europe
, the French "Wonder Lights" and Ever Ready brands gradually disappeared in favour of American, Japanese and German products.
In recent times there have been many advances: exceptionally efficient dynamo
s; cheap high-output sealed-unit halogen lamp
s originally developed for decorative lighting; improved storage density in rechargeable batteries driven by the computer industry; high-output light emitting diodes (LEDs); white LEDs; high intensity discharge (HID) lights crossing over from the automotive sector.
, either rechargeable or disposable
, are often used to power electric bicycle lights. For bicycle touring
, commuting or if battery operation is otherwise unwanted an electrical generator, or dynamo, may be used. (While "dynamo
" generally refers to a generator that produces direct current with the use of a commutator
, cycling usage normally refers to an alternating current magneto
.) Unlike batteries, a dynamo has unlimited duration, but the maximum power output is relatively low. This is somewhat mitigated by good optics and slight overvolting of the lamp; a good dynamo nominally rated at 6 V is generally allowed to produce 7 V or so by its voltage limiting circuitry. In Germany
, it is illegal to use bicycles without a dynamo-based lighting system except on "racing bicycles" below 11 kg. This has stimulated the market for high quality dynamos such as B&M or Schmidt. Some tweaks have been done to put toggle switches on the lighting, and small rechargeable batteries in line with the dynamo during daytime hours to ensure continuous output of light when stopped.
Other electric systems include 12 volt lighting with sealed lead-acid batteries since they can also provide power for air compressors that fit in automotive cigar lighter receptacle
s when tires go flat. they are useful for other functions such as extending cell phone battery life, since cell phones are becoming more and more relied on by travellers.
Often supplied by 2 AA or C/D cell batteries.
6 volt:
Sometimes 4 AA batteries are used; also supplied from bottle or hub dynamos, and lead-acid batteries
9 volt:
Sometimes supplied by PP3 batteries
12 volt:
Mostly supplied by sealed lead-acid batteries
. The main advantage with this voltage is versatility of the electric system, such as the ability to charge a cell phone battery with a cigar lighter receptacle
as cell phones are now becoming more and more needed for users. It also allows electric air compressors to fix flat tires. Some 12 volt dynamos are available too.
, but requires special circuitry and a powerful battery. Filament based lamps have largely been superseded by high efficiency white light-emitting diode
(LED) headlights, which combine lower expense, higher light output, and longer battery life. The best LED systems may soon make even HID systems obsolete.
Red tail lights have traditionally combined a white light source with a red filter
, which wastes power creating light that will not be transmitted. Red LEDs emit only red light in the first place, and hence consume much less energy.
The type of lights used may depend on the available power sources and the amount of light required, but as often reflects personal preference or local availability. A low power headlight and a rear red LED suffice for cycling at low speeds in familiar areas with street lights. Unlit and unfamiliar areas demand a more powerful headlight for safety, at the cost of greater weight, higher cost, or shorter run time.
A common setup for a bicycle commuter
might include:
(1968) of the United Nations
, a bicycle is a vehicle. Article 44 of the Convention stipulates that: "Cycles without an engine in international traffic shall: (c) Be equipped with a red reflecting device at the rear and with devices such that the cycle can show a white or selective-yellow light to the front and a red light to the rear." In some countries, for example France
, it may be an offence to even sell a bicycle not fitted with legally compliant lighting system. Germany requires that all bikes over 11 kg be fitted with compliant dynamo lighting systems, but even lightweight bikes are required to be fitted with lights (battery powered lights allowed) except when racing. However not all countries impose this requirement on their domestic cyclists.
Many jurisdictions require bicycles to be fitted with reflectors at point of sale. In the United States
this is regulated by the Consumer Product Safety Commission
. CPSC compliant reflectors (also commonly fitted in other markets) have three retro-reflective panels positioned at 30° angles. The standard requires a forward-facing white reflector on the front of the bicycle, sideways-facing white reflectors on each wheel, a red reflector mounted on the rear, and yellow reflectors mounted on the front and back of each pedal. Some interpret this as an endorsement of reflector-only night cycling.
Many jurisdictions require the use of a headlight and a rear light or reflector after dark. Most European countries and some US states require front and rear lights at night, while others allow reflectors only at the rear. Individual jurisdictions define specific legal requirements in terms of light output and the size of lamp and reflector lenses, compliance with specified standards, or simply stipulate a minimum distance from which any lighting device should be visible. In some jurisdictions, some systems involving LED based flashers are illegal because blinking lights are only allowed on emergency vehicles, but those rules are rarely enforced.
In the UK, the regulations governing bicycle lights are set out in the Road Vehicles Lighting Regulations 1989 and their subsequent amendments, summarized in the Highway Code. The regulations require a white front light, a red rear light, a red rear reflector,
and amber/yellow pedal reflectors on the front and rear of both pedals.
Reflectors must conform to BS 6102/2 or an equivalent European standard. The situation for lights is more complicated:
The majority of LED lights available are not approved for UK use since they have steady modes that do not conform to BS 6102/3. It is, however, legal to fit additional lights providing that they are of the correct colour, they do not dazzle other road users and that if they flash, they do so at a constant rate of between 60 and 240 flashes per minute.
National cyclists' organisations such as LAB (US) or CTC (UK) are a source of lighting information.
between collisions and failure to use lights even during daytime.
It is generally believed that reflectors alone are inadequate for night riding (almost all cycling organisations unconditionally advocate using a headlight at night), but the Consumer Product Safety Commission
and other regulatory agencies have declined to mandate the inclusion of active headlamps with new bicycles, citing increased costs compared to benefits and the fact that most bicycles are not ridden at night.
It has been estimated that 75% of bicycles used in the United States at night do not meet the legal requirements for lighting. This may be because the majority of unlit cyclists are riding in urban areas with many streetlights, and bicycles are not required to be sold with a headlight.
In countries where bicycles are used widely for commuting and short trips, such as the Netherlands
and Scandinavia
, bicycle head- and tail lighting regulation is heavily enforced by the authorities.
front light and rear LED flasher. Red or yellow LEDs suitable for use as rear lights have been available for many years. Recently, white LEDs which satisfy the requirements for a front light have come on the market, and some jurisdictions have made or are considering making these legally acceptable. Very high-power LEDs are sensitive to overheating and over-driving, if the enclosure or driving electronics are poorly designed. Both of these conditions significantly shorten the LED's lifespan, causing them to dim or completely burn out, and LEDs are expensive to replace. Most LEDs have a higher luminous efficacy
than halogen lights, but poorly designed driving electronics can negate the advantage.
Low-power LEDs are sufficient for riding on well-lit streets, but do not generally project a very bright beam as it is difficult to collimate
the output from multiple LEDs into a single usable beam. This can be overcome by using a few very high-power LEDs - each with their own optics. It is now possible to buy LED equivalents for halogen rechargeable systems (including drop-in replacement bulbs), and LED lights for dynamos. On a dynamo, LEDs produce more light than halogen lights at very low speeds (down to 3 km/h according to one manufacturer).
High-power LED systems often include an option to dim the LEDs. LEDs are well-suited to dimming, as halving the brightness usually more than doubles the battery life. By contrast, halving the brightness of a halogen bulb only slightly increases battery life.
Efficiency is set to increase, as LED technology continues to follow a Moore's Law
pattern of exponential efficiency and cost improvements. As very high power LED lights become available and start to replace halogen designs, they may replace incandescent lamps whatever the power source, and are now surpassing Xenon HID lights. A 3-watt
LED offers similar light output to a basic 10-watt halogen bulb - compare this with current generation "very high brightness" LEDs at 0.05 watts.
Advantages
Disadvantages
Low power LED lights are mainly for "being seen", or as an emergency backup, and are the dominant choice for rear lights.
Home made LED lights
As with high-power halogen systems, high-power LED systems have attracted self-build enthusiasts, as top-end commercial products tend to be expensive due to low production volumes. Home brewers can incorporate state of the art technology months or years before it reaches the marketplace in retail products.
Advantages of low-cost battery lights
Disadvantages
Advantages of rechargeable flashlights
Disadvantages
, lead-acid, or Li-ion rechargeable battery pack.
The lights used by most halogen rechargeable systems are cheap, bright but fairly simple: they project a cone of light (wide and narrow beam options are available) which is good for off-road use but not ideal for road use as it can dazzle oncoming road users. This is why rechargeable halogen lights do not meet legal requirements in some jurisdictions.
Many systems use standard commercial prefocused optics, making a wide range of power and beam width combinations available. Most systems allow simultaneous connection of different lamps - for example, a wide and a narrow beam for off-road riding, or a high- and a low-power beam for road riding.
Advantages of rechargeable halogen systems
Disadvantages
High-intensity discharge (HID) lights are the brightest lights currently available for bikes. They are very efficient, very bright, but expensive. They also tend to have high power consumption (although they use less power than halogens for higher output), so a relatively limited burn time. Otherwise they have the same advantages and disadvantages as rechargeable halogen systems, and like halogen systems they are designed primarily for off-road use, having rotationally symmetrical beams which cast as much light up as down. An additional disadvantage compared with halogen or LED lights is that the HID lamp does not tolerate repeated strikes, and in many cases does not relight immediately after shutting down. Likewise, should the battery level fall too low, the lamp will shut down rather than dimming. But the longer battery life than halogens tends to negate these problems, as many riders simply switch the light on and leave it running throughout the ride.
Advantages of rechargeable HID systems
Disadvantages
If using a HID lighting system on the road, lights should be adjusted to avoid dazzling oncoming traffic.
which must be visible through a very wide arc. Newer LED lights have this feature, removing even this final advantage. Energizer once made a 2.4W halogen rear lamp, which was essentially a headlamp with a red lens, but most rear lights only need to be around 0.5W.
Most LED lights will work in either flashing or steady modes. Some LED lights have multiple banks of LEDs allowing both flashing and steady light at once. This can also be achieved by having one flashing light and one steady one.
In many countries, LED flashers are the norm for rear lights. In others such as Germany
flashing lights are forbidden by law. In the UK flashing LEDs (front and rear) are legal from October 2005, provided that the lights conform to the requirements of the current Road Vehicles Lighting regulations. Many vendors claim EU compliance, however this provides no consistent safety or legal value across the Union.
The most common power source for rear LEDs is a set of alkaline cells and rechargeable cells. In both cases the battery tends to fail quickly when it goes; it is widely considered good practice to have two rear lights in case a battery fails en route.
Advantages of LED rear lights
Advantages of xenon strobes
Disadvantages
bicycle patrol are outfitted with special colored lighting, generally blue and red, to alert the surrounding public of the officer's presence. These lights can flash in a variety of patterns, sometimes supplemented with a siren
, to help the officer make his or her way through crowded streets or sidewalks in case of emergency. A popular method of supplying power to police bicycle lights is to encase the battery in a bottle-shaped container which can fit into the bicycle's water bottle holder.
(LSD-NiMH) in 2005 made rechargeable AA
and AAA
sized batteries more viable for powering LED bicycle lights. Previously, the self-discharge effect of NiCAD and NiMH
batteries caused the battery to run down over a period of weeks or a few months, even when not in use. This was particularly a problem for low powered LED lights, and for users who only used their bicycle lights occasionally. The LSD-NiMH battery greatly reduced the self-discharge effect, allowing the battery to keep its charge for a year or more.
For higher-powered lights, an external battery pack of 12V sealed lead acid battery is often required. These battery packs usually strap to one of the horizontal bars on the bike, or come in the shape of a water bottle to mount in the bike's water bottle holder, or can be placed in a basket. A cable connects the battery pack to the light.
Dynamo
systems require no batteries to recharge or replace, and may be permanently fitted to the bike. Bicycle dynamos produce alternating current
, so are more correctly called "alternator
s" or "generators
", but the word "dynamo" is also popular.
s are built into the front or rear wheel hub, and are generally the most efficient; bottle dynamo
s attach to the seatstay or fork and are rotated by a small wheel in contact with the tire sidewall, they are generally easiest to obtain and cheapest while European-designed tyres generally feature a raised "track" to run the generator's wheel; bottom bracket dynamos bolt between the chainstays behind the bottom bracket and are powered by a roller against the tyre, these are easy to fit and do not wear the tire sidewall. A fourth type is a spoke-mounted electromagnetic system.
s to prevent it, and dynamos can be designed to "saturate" beyond a certain voltage to protect the lamp (saturation is a feature of all permanent magnet generators). Good dynamos can achieve efficiencies of up to 70% (i.e., under 5 W of the rider's output is diverted to produce 3 W of electricity) and provide full output at surprisingly low speeds, often 4 to 6 mph (6 to 10 km/h) is sufficient for full brightness.
To compensate for their limited output, dynamo headlights have good optics which focus the limited amount of light in a narrow beam that lights up the road directly in front of the bicycle; this can be seen in Andreas Oehler's side-by side comparison of beam patterns.
To produce light when the bike is stationary, some dynamo lights have a stand light facility, usually a single blue-white LED powered by a capacitor
, which runs for around five minutes. It is now common to use all the dynamo's output to power the front light; the alternative is a 2.4 W headlight and a 0.6 W tail light. Most good dynamo rear lights now use LEDs instead of incandescent lamps. Increasingly, dynamo headlights use LED light sources for the main beam as well as the standlight; some manufacturers include B&M, Supernova (both German) and Solidlights (British). In these newer lamps, the dynamo output requires substantial cleaning up and rectification by electronics before it can be used to drive an LED, whereas a conventional filament lamp will run happily on the "raw" AC from the dynamo.
Some riders consider the output of dynamo lighting insufficient. Others report that it is adequate to see on dark roads at speeds up to about 20 mph (32.19 km/h), (single 3 W) or more if a 12 V system is used. LED headlights typically give 2-3 times the light output of a halogen lamp for the same power, due to their greater efficiency.
. The lights are mounted on the bike wheels, eliminating the need for batteries. The advantages are pretty much the same as with dynamo lighting while incurring less resistance to the rider than traditional dynamos and eliminating the noise and wear of the tire.
Some rechargeable systems offer a head torch option powered from the main battery pack.
, in the form of reflectors, reflective tape, and reflective clothing, are useful in making a cyclist visible to other road users. Reflective materials can be applied to bike, rider, luggage, and tyres are available with reflective sidewalls.
have suggested that the requirement could be waived if the cyclist fits an additional rear reflector and/or lighting, but this was not changed in the last revision of the UK vehicle lighting laws (which permitted flashing LEDs). Riders of recumbent bicycle
s have pointed out that the pedal reflector requirement is nonsensical for them, since the reflectors point straight up and down in use, and are invisible from other vehicles. As of 2008, California law allows white or yellow shoe reflectors (front and back), or reflective ankle bands, in lieu of pedal reflectors.
Reflectives are visible only when in the beam of a headlight, and even then only within a narrow locus. Importantly, they do nothing to light up the road. Reflectors are not a substitute for lights.
On dark roads reflective materials such as 3M's Scotchlite
will show up boldly in car headlights. Evidence shows that bright material on the sleeves can prompt drivers to give more passing distance . Retroreflective materials can discourage some oncoming motorists from dipping their headlights, as the rider become less visible if they do.
The colour of lighting should be checked in the rider's area. A single solid colour can disappear under artificial light, particularly yellow sodium vapour lighting, and colour blindness is common; red/green colourblindness can make yellow fluorescent vanish against a green background (hedges or grass), although people with red/green colourblindness dispute this. Vests with both yellow and orange fluorescent plus wide strips of reflective may be the best solution.
In recent times electroluminescent
clothing has become available to add to the existing array of LED-illuminated armbands and helmet blinkies. An electroluminescent
helmet has been patented.
s, measuring the intensity
of a beam, are more appropriate when the aim is to illuminate brightly a small spot, while lumen
s, measuring the entire production of light, are more relevant to the purposes of broad beams or non-directional running lights.
, and is usually quoted for the electrical power input, not the light power output. Electrical power is the product of voltage and current (watts = volt
s × ampere
s). Input power is only useful when comparing lights of similar technologies. A 3 W halogen dynamo headlight will light the road up about the same as a rechargeable light of around 7–10 W, but the rechargeable usually outputs much more light to the sides, which is useful on trails (although wide and narrow beam versions are available). A 3 W LED is somewhat brighter than a halogen lamp but generally less well focused. HID lights put out large amounts of light and are often quoted in terms like "80 W halogen equivalent".
, that is power per unit solid angle
, weighted according to the sensitivity of the human eye to various colours of light. A typical candle
produces light with about 1 candela of luminous intensity. A lamp can produce higher luminous intensity either by producing more light, or by focusing it tighter. The luminous intensity of a light depends on many factors, including the colour of the light and the eye's sensitivity to that colour, the optics involved, reflector and lens. Despite its complexity, it is a more useful measure than watts, because it defines how much usable light is shed in a given place: a dynamo headlight designed for road use and focused for seeing the road makes more efficient use of the power of the lamp than lights using rotationally symmetrical optics.
, the total amount of light emitted by a source, weighted according to the sensitivity of the human eye to various colours of light. Lumens per watt is a common measure of the efficiency of a light source. The luminous flux is of less value for bicycle lighting due to the importance of directionality. Luminous intensity is much more useful, but lumens per watt is a handy way to compare the output of otherwise similar lights.
Bicycle
A bicycle, also known as a bike, pushbike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A person who rides a bicycle is called a cyclist, or bicyclist....
rider to others in dark conditions, i.e. to increase the rider's conspicuity and to enhance the ability of the rider to see, illuminating the way forward. Both reflectors and active lights are used to make the rider more visible, and many jurisdictions require one or more types of light to be fitted to bikes ridden at night. White light in the front, red lights in the back, with orange reflectors on the side is the most common setup. Many types of light sources are used for bicycle lights.
History
Carbide lamp
Carbide lamps, properly known as acetylene gas lamps, are simple lamps that produce and burn acetylene which is created by the reaction of calcium carbide with water....
s were powered by acetylene gas, produced by combining calcium carbide
Calcium carbide
thumb|right|Calcium carbide.Calcium carbide is a chemical compound with the chemical formula of CaC2. The pure material is colorless, however pieces of technical grade calcium carbide are grey or brown and consist of only 80-85% of CaC2 . Because of presence of PH3, NH3, and H2S it has a...
with water. The light given was very bright, although the lamps required regular maintenance; the arrival of battery-powered lamps in the 1890s was well received.
Early battery lamps generally used a lead-acid battery
Lead-acid battery
Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large...
, but these were replaced by self-contained dry cells
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
; lamps became smaller and more reliable. At the same time dynamo
Dynamo
- Engineering :* Dynamo, a magnetic device originally used as an electric generator* Dynamo theory, a theory relating to magnetic fields of celestial bodies* Solar dynamo, the physical process that generates the Sun's magnetic field- Software :...
s were developed which generated energy from the bicycle's own movement. These were more practical, as storage density in batteries was at this time very low.
Not all jurisdictions required use of lights after dark. In the UK the law requiring use of rear lights was resisted by cyclists' groups on the grounds that it downplayed motorists' obligation to be able to stop well within the distance they can see to be clear.
Replaceable-cell battery lights had a renaissance on the invention of the alkaline battery
Alkaline battery
Alkaline batteries are a type of primary batteries dependent upon the reaction between zinc and manganese dioxide . A rechargeable alkaline battery allows reuse of specially designed cells....
, with a much higher storage density. Moulding techniques for plastics also improved, allowing lens
Lens (optics)
A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
optics
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
to be refined at low cost thus making more efficient use of the light output. During the 1980s the lighting market became more globalised: in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, the French "Wonder Lights" and Ever Ready brands gradually disappeared in favour of American, Japanese and German products.
In recent times there have been many advances: exceptionally efficient dynamo
Dynamo
- Engineering :* Dynamo, a magnetic device originally used as an electric generator* Dynamo theory, a theory relating to magnetic fields of celestial bodies* Solar dynamo, the physical process that generates the Sun's magnetic field- Software :...
s; cheap high-output sealed-unit halogen lamp
Halogen lamp
A halogen lamp, also known as a tungsten halogen lamp, is an incandescent lamp with a tungsten filament contained within an inert gas and a small amount of a halogen such as iodine or bromine. The chemical halogen cycle redeposits evaporated tungsten back on to the filament, extending the life of...
s originally developed for decorative lighting; improved storage density in rechargeable batteries driven by the computer industry; high-output light emitting diodes (LEDs); white LEDs; high intensity discharge (HID) lights crossing over from the automotive sector.
Electrical system
BatteriesBattery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
, either rechargeable or disposable
Disposable
A disposable is a product designed for cheapness and short-term convenience rather than medium to long-term durability, with most products only intended for single use. The term is also sometimes used for products that may last several months to distinguish from similar products that last...
, are often used to power electric bicycle lights. For bicycle touring
Bicycle touring
Bicycle touring is cycling over long distances – prioritizing pleasure and endurance over utility or speed. Touring can range from single day 'supported' rides — e.g., rides to benefit charities — where provisions are available to riders at stops along the route, to multi-day...
, commuting or if battery operation is otherwise unwanted an electrical generator, or dynamo, may be used. (While "dynamo
Dynamo
- Engineering :* Dynamo, a magnetic device originally used as an electric generator* Dynamo theory, a theory relating to magnetic fields of celestial bodies* Solar dynamo, the physical process that generates the Sun's magnetic field- Software :...
" generally refers to a generator that produces direct current with the use of a commutator
Commutator (electric)
A commutator is a rotary electrical switch in certain types of electric motors or electrical generators that periodically reverses the current direction between the rotor and the external circuit. In a motor, it applies power to the best location on the rotor, and in a generator, picks off power...
, cycling usage normally refers to an alternating current magneto
Magneto
A magneto is a type of electrical generator.Magneto may also refer to:* Magneto , permanent magnetic alternating current rotary generator* ignition magneto, magnetos on internal combustion engines...
.) Unlike batteries, a dynamo has unlimited duration, but the maximum power output is relatively low. This is somewhat mitigated by good optics and slight overvolting of the lamp; a good dynamo nominally rated at 6 V is generally allowed to produce 7 V or so by its voltage limiting circuitry. In Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, it is illegal to use bicycles without a dynamo-based lighting system except on "racing bicycles" below 11 kg. This has stimulated the market for high quality dynamos such as B&M or Schmidt. Some tweaks have been done to put toggle switches on the lighting, and small rechargeable batteries in line with the dynamo during daytime hours to ensure continuous output of light when stopped.
Other electric systems include 12 volt lighting with sealed lead-acid batteries since they can also provide power for air compressors that fit in automotive cigar lighter receptacle
Cigar lighter receptacle
The cigarette lighter receptacle in an automobile, initially designed to power an electrically heated lighter, became a de-facto standard DC connector to supply electrical power for portable accessories used in or near an automobile...
s when tires go flat. they are useful for other functions such as extending cell phone battery life, since cell phones are becoming more and more relied on by travellers.
Voltages
3 volt:Often supplied by 2 AA or C/D cell batteries.
6 volt:
Sometimes 4 AA batteries are used; also supplied from bottle or hub dynamos, and lead-acid batteries
9 volt:
Sometimes supplied by PP3 batteries
12 volt:
Mostly supplied by sealed lead-acid batteries
Lead-acid battery
Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large...
. The main advantage with this voltage is versatility of the electric system, such as the ability to charge a cell phone battery with a cigar lighter receptacle
Cigar lighter receptacle
The cigarette lighter receptacle in an automobile, initially designed to power an electrically heated lighter, became a de-facto standard DC connector to supply electrical power for portable accessories used in or near an automobile...
as cell phones are now becoming more and more needed for users. It also allows electric air compressors to fix flat tires. Some 12 volt dynamos are available too.
Light sources
The simplest bicycle headlights use a tungsten filament lamp. A more expensive, but brighter and more efficient alternative is the halogen lamp. A high intensity discharge (HID) light provides greater light intensityLuminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye...
, but requires special circuitry and a powerful battery. Filament based lamps have largely been superseded by high efficiency white light-emitting diode
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
(LED) headlights, which combine lower expense, higher light output, and longer battery life. The best LED systems may soon make even HID systems obsolete.
Red tail lights have traditionally combined a white light source with a red filter
Filter (optics)
Optical filters are devices which selectively transmit light of different wavelengths, usually implemented as plane glass or plastic devices in the optical path which are either dyed in the mass or have interference coatings....
, which wastes power creating light that will not be transmitted. Red LEDs emit only red light in the first place, and hence consume much less energy.
The type of lights used may depend on the available power sources and the amount of light required, but as often reflects personal preference or local availability. A low power headlight and a rear red LED suffice for cycling at low speeds in familiar areas with street lights. Unlit and unfamiliar areas demand a more powerful headlight for safety, at the cost of greater weight, higher cost, or shorter run time.
A common setup for a bicycle commuter
Bicycle commuting
Bicycle commuting is the use of a bicycle to travel from home to a place of work or study — in contrast to the use of a bicycle for sport, recreation or touring....
might include:
- a quartz-halogen or high power LED headlight powered by a rechargeable battery pack or dynamo
- a LED tail light, either steady or flashing/pulsating
- a flashing/pulsating LED front light for conspicuousness and as backup
Legal requirements
Under the International Vienna Convention on Road TrafficVienna Convention on Road Traffic
The Vienna Convention on Road Traffic is an international treaty designed to facilitate international road traffic and to increase road safety by standardising the uniform traffic rules among the contracting parties...
(1968) of the United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...
, a bicycle is a vehicle. Article 44 of the Convention stipulates that: "Cycles without an engine in international traffic shall: (c) Be equipped with a red reflecting device at the rear and with devices such that the cycle can show a white or selective-yellow light to the front and a red light to the rear." In some countries, for example France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, it may be an offence to even sell a bicycle not fitted with legally compliant lighting system. Germany requires that all bikes over 11 kg be fitted with compliant dynamo lighting systems, but even lightweight bikes are required to be fitted with lights (battery powered lights allowed) except when racing. However not all countries impose this requirement on their domestic cyclists.
Many jurisdictions require bicycles to be fitted with reflectors at point of sale. In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
this is regulated by the Consumer Product Safety Commission
Consumer Product Safety Commission
The United States Consumer Product Safety Commission is an independent agency of the United States government created in 1972 through the Consumer Product Safety Act to protect "against unreasonable risks of injuries associated with consumer products." The CPSC is an independent agency that does...
. CPSC compliant reflectors (also commonly fitted in other markets) have three retro-reflective panels positioned at 30° angles. The standard requires a forward-facing white reflector on the front of the bicycle, sideways-facing white reflectors on each wheel, a red reflector mounted on the rear, and yellow reflectors mounted on the front and back of each pedal. Some interpret this as an endorsement of reflector-only night cycling.
Many jurisdictions require the use of a headlight and a rear light or reflector after dark. Most European countries and some US states require front and rear lights at night, while others allow reflectors only at the rear. Individual jurisdictions define specific legal requirements in terms of light output and the size of lamp and reflector lenses, compliance with specified standards, or simply stipulate a minimum distance from which any lighting device should be visible. In some jurisdictions, some systems involving LED based flashers are illegal because blinking lights are only allowed on emergency vehicles, but those rules are rarely enforced.
In the UK, the regulations governing bicycle lights are set out in the Road Vehicles Lighting Regulations 1989 and their subsequent amendments, summarized in the Highway Code. The regulations require a white front light, a red rear light, a red rear reflector,
and amber/yellow pedal reflectors on the front and rear of both pedals.
Reflectors must conform to BS 6102/2 or an equivalent European standard. The situation for lights is more complicated:
- a light with a steady mode is considered approved only if it conforms to BS 6102/3 or an equivalent European standard;
- a light without a steady mode is considered approved only if it flashes at a constant rate of between 60 to 240 flashes per minute and has a luminous intensity of at least 4 candela;
The majority of LED lights available are not approved for UK use since they have steady modes that do not conform to BS 6102/3. It is, however, legal to fit additional lights providing that they are of the correct colour, they do not dazzle other road users and that if they flash, they do so at a constant rate of between 60 and 240 flashes per minute.
National cyclists' organisations such as LAB (US) or CTC (UK) are a source of lighting information.
Safety
The use of lights for night riding is generally recommended or required by authorities as a basic safety precaution, even in a well-lit urban context. Studies show a correlationCorrelation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
between collisions and failure to use lights even during daytime.
It is generally believed that reflectors alone are inadequate for night riding (almost all cycling organisations unconditionally advocate using a headlight at night), but the Consumer Product Safety Commission
Consumer Product Safety Commission
The United States Consumer Product Safety Commission is an independent agency of the United States government created in 1972 through the Consumer Product Safety Act to protect "against unreasonable risks of injuries associated with consumer products." The CPSC is an independent agency that does...
and other regulatory agencies have declined to mandate the inclusion of active headlamps with new bicycles, citing increased costs compared to benefits and the fact that most bicycles are not ridden at night.
It has been estimated that 75% of bicycles used in the United States at night do not meet the legal requirements for lighting. This may be because the majority of unlit cyclists are riding in urban areas with many streetlights, and bicycles are not required to be sold with a headlight.
In countries where bicycles are used widely for commuting and short trips, such as the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
and Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
, bicycle head- and tail lighting regulation is heavily enforced by the authorities.
LEDs
Cyclists who only occasionally ride at night may opt for an inexpensive LEDLight-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
front light and rear LED flasher. Red or yellow LEDs suitable for use as rear lights have been available for many years. Recently, white LEDs which satisfy the requirements for a front light have come on the market, and some jurisdictions have made or are considering making these legally acceptable. Very high-power LEDs are sensitive to overheating and over-driving, if the enclosure or driving electronics are poorly designed. Both of these conditions significantly shorten the LED's lifespan, causing them to dim or completely burn out, and LEDs are expensive to replace. Most LEDs have a higher luminous efficacy
Luminous efficacy
Luminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total electric power consumed by the source.Which sense of the term is...
than halogen lights, but poorly designed driving electronics can negate the advantage.
Low-power LEDs are sufficient for riding on well-lit streets, but do not generally project a very bright beam as it is difficult to collimate
Collimated light
Collimated light is light whose rays are parallel, and therefore will spread slowly as it propagates. The word is related to "collinear" and implies light that does not disperse with distance , or that will disperse minimally...
the output from multiple LEDs into a single usable beam. This can be overcome by using a few very high-power LEDs - each with their own optics. It is now possible to buy LED equivalents for halogen rechargeable systems (including drop-in replacement bulbs), and LED lights for dynamos. On a dynamo, LEDs produce more light than halogen lights at very low speeds (down to 3 km/h according to one manufacturer).
High-power LED systems often include an option to dim the LEDs. LEDs are well-suited to dimming, as halving the brightness usually more than doubles the battery life. By contrast, halving the brightness of a halogen bulb only slightly increases battery life.
Efficiency is set to increase, as LED technology continues to follow a Moore's Law
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
pattern of exponential efficiency and cost improvements. As very high power LED lights become available and start to replace halogen designs, they may replace incandescent lamps whatever the power source, and are now surpassing Xenon HID lights. A 3-watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
LED offers similar light output to a basic 10-watt halogen bulb - compare this with current generation "very high brightness" LEDs at 0.05 watts.
Advantages
- High luminous efficacyLuminous efficacyLuminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total electric power consumed by the source.Which sense of the term is...
leading to long battery life - Lifetime around 50000 hours of operation if current and temperature is managed
- Can be dimmed, usually with a slight gain in efficiency
- Instantaneous turn on/off and blinking
Disadvantages
- Limited light output per single LED - overcome by multi LED lights
- High power LEDs require a constant current source making them more expensive to manufacture but as a result do not dim through use
- Illegal in some jurisdictions
Low power LED lights are mainly for "being seen", or as an emergency backup, and are the dominant choice for rear lights.
Home made LED lights
Low-cost battery lights
Low-cost battery lights can be a good choice for occasional use, and usually meet legislative requirements. But the saving can often be negated by poor battery life. These lights are low-power but compensate this to some extent with good optics. Some newer models have LEDs instead of halogen lamps, which are illegal in some jurisdictions.Advantages of low-cost battery lights
- Low cost
- Readily available (both lights and batteries)
Disadvantages
- Cost of batteries, unless they are rechargeable. This stops it being "low-cost" due to the amount of batteries used over time.
- Generally low power
Flashlights
There are some high-power flashlights with rechargeable lithium-ion batteries. Although not specifically designed for bicycle use, these are a viable alternative to rechargeable halogen lights, though they are still expensive. They can be fastened to the bicycle handlebars with various mounting devices such as a "lock-block". Although the optics of these flashlights are generally high quality they are still rotationally symmetrical (unlike motor vehicle lights).Advantages of rechargeable flashlights
- Versatile - can also be used as a flashlight off the bike
- Portable, so theft resistant
Disadvantages
- Limited burn time
- Heavy (rechargeable systems generally separate the weight of the battery from the lamp); weight may be an issue for off-road riders due to vibration
- Optics not optimised for road use
- Sometimes difficult to mount on the bike, which also leads to a safety issue—if a light falls off its mount, it may fall into and block the front wheel and cause it to immediately stop, typically causing the bike to flip.
Halogen lights
Although these lights were primarily designed for off-road use, where they are almost universal, many commuters and transportational cyclists now choose to use high-power halogen front lights which operate from a NiMHNIMH
NIMH or NiMH may refer to:*Nickel-metal hydride battery, a type of rechargeable battery*National Institute of Mental Health, a part of the United States National Institutes of Health...
, lead-acid, or Li-ion rechargeable battery pack.
The lights used by most halogen rechargeable systems are cheap, bright but fairly simple: they project a cone of light (wide and narrow beam options are available) which is good for off-road use but not ideal for road use as it can dazzle oncoming road users. This is why rechargeable halogen lights do not meet legal requirements in some jurisdictions.
Many systems use standard commercial prefocused optics, making a wide range of power and beam width combinations available. Most systems allow simultaneous connection of different lamps - for example, a wide and a narrow beam for off-road riding, or a high- and a low-power beam for road riding.
Advantages of rechargeable halogen systems
- High power output
- Readily available
- Reasonable battery capacity
- Very reliable
- Can usually be easily removed from the bicycle or to prevent theft
- Lamps are cheap and widely available.
Disadvantages
- Limited run-time between battery recharges
- Hassle of being certain to keep batteries charged
- Batteries have limited life, typically 500-1000 recharge cycles
- Power cycling reduces lamp life
HID lights
Advantages of rechargeable HID systems
- Very high power output
- High luminous efficacyLuminous efficacyLuminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total electric power consumed by the source.Which sense of the term is...
Disadvantages
- Expensive
- Lamp requires warm up before reaching full output power and/or luminous efficacyLuminous efficacyLuminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total electric power consumed by the source.Which sense of the term is...
- Inefficient on medium power settings
- Unable to run on very low power due to being unable to maintain the arc that generates the light
If using a HID lighting system on the road, lights should be adjusted to avoid dazzling oncoming traffic.
Filament lamps
The only real advantage to these is that they are often omnidirectional, a quality useful in running lightsRunning lights
On vehicles, running lights are designed to increase visibility while moving. It may refer to:* Automotive lighting, for running lights for cars* Bicycle lighting, for running lights for bicycles...
which must be visible through a very wide arc. Newer LED lights have this feature, removing even this final advantage. Energizer once made a 2.4W halogen rear lamp, which was essentially a headlamp with a red lens, but most rear lights only need to be around 0.5W.
LEDs
Most LED lights will work in either flashing or steady modes. Some LED lights have multiple banks of LEDs allowing both flashing and steady light at once. This can also be achieved by having one flashing light and one steady one.
In many countries, LED flashers are the norm for rear lights. In others such as Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
flashing lights are forbidden by law. In the UK flashing LEDs (front and rear) are legal from October 2005, provided that the lights conform to the requirements of the current Road Vehicles Lighting regulations. Many vendors claim EU compliance, however this provides no consistent safety or legal value across the Union.
The most common power source for rear LEDs is a set of alkaline cells and rechargeable cells. In both cases the battery tends to fail quickly when it goes; it is widely considered good practice to have two rear lights in case a battery fails en route.
Advantages of LED rear lights
- Compared with incandescent lamps, near-infinite service life
- Bright
- High luminous efficacyLuminous efficacyLuminous efficacy is a measure of how well a light source produces visible light. It is the ratio of luminous flux to power. Depending on context, the power can be either the radiant flux of the source's output, or it can be the total electric power consumed by the source.Which sense of the term is...
- Cheap
- Usually a choice of flashing or steady
Xenon strobes
An innovation in bicycle lighting, though common in industrial applications, xenon strobes are brighter than LEDs and are used by some as rear lights.Advantages of xenon strobes
- Very bright
Disadvantages
- Relatively expensive
- High power consumption (short battery life)
- Lamps require fairly frequent replacement
- Intense light can be a serious irritation to other road users
- Brief flash followed by darkness, can interfere with night vision and make judgement of cyclist's position difficult.
Police bicycles
Bicycles intended for policePolice
The police is a personification of the state designated to put in practice the enforced law, protect property and reduce civil disorder in civilian matters. Their powers include the legitimized use of force...
bicycle patrol are outfitted with special colored lighting, generally blue and red, to alert the surrounding public of the officer's presence. These lights can flash in a variety of patterns, sometimes supplemented with a siren
Siren
In Greek mythology, the Sirens were three dangerous mermaid like creatures, portrayed as seductresses who lured nearby sailors with their enchanting music and voices to shipwreck on the rocky coast of their island. Roman poets placed them on an island called Sirenum scopuli...
, to help the officer make his or her way through crowded streets or sidewalks in case of emergency. A popular method of supplying power to police bicycle lights is to encase the battery in a bottle-shaped container which can fit into the bicycle's water bottle holder.
Batteries
The introduction of the Low self-discharge NiMH batteryLow self-discharge NiMH battery
The low self-discharge nickel-metal hydride battery was introduced in November 2005. These batteries were developed by Sanyo, who called them "eneloop". Subsequently, other manufacturers also offered LSD NiMH....
(LSD-NiMH) in 2005 made rechargeable AA
AA battery
An AA battery is a standard size of battery. Batteries of this size are the most commonly used type of in portable electronic devices. An AA battery is composed of a single electrochemical cell...
and AAA
AAA battery
A triple A or AAA battery is a standard size of dry cell battery commonly used in portable electronic devices. A carbon-zinc battery in this size is designated by IEC as "R03", by ANSI C18.1 as "24", by old JIS standard as "UM 4", and by other manufacturer and national standard designations that...
sized batteries more viable for powering LED bicycle lights. Previously, the self-discharge effect of NiCAD and NiMH
NIMH
NIMH or NiMH may refer to:*Nickel-metal hydride battery, a type of rechargeable battery*National Institute of Mental Health, a part of the United States National Institutes of Health...
batteries caused the battery to run down over a period of weeks or a few months, even when not in use. This was particularly a problem for low powered LED lights, and for users who only used their bicycle lights occasionally. The LSD-NiMH battery greatly reduced the self-discharge effect, allowing the battery to keep its charge for a year or more.
For higher-powered lights, an external battery pack of 12V sealed lead acid battery is often required. These battery packs usually strap to one of the horizontal bars on the bike, or come in the shape of a water bottle to mount in the bike's water bottle holder, or can be placed in a basket. A cable connects the battery pack to the light.
Dynamo systems
Dynamo
- Engineering :* Dynamo, a magnetic device originally used as an electric generator* Dynamo theory, a theory relating to magnetic fields of celestial bodies* Solar dynamo, the physical process that generates the Sun's magnetic field- Software :...
systems require no batteries to recharge or replace, and may be permanently fitted to the bike. Bicycle dynamos produce alternating current
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
, so are more correctly called "alternator
Alternator
An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...
s" or "generators
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
", but the word "dynamo" is also popular.
Types
There are three main types: hub dynamoHub dynamo
A hub dynamo is a small electrical generator built into the hub of a bicycle wheel that is usually used to power lights. Most modern hub dynamos are regulated to 3 watts at 6 volts, although some will drive up to 6 watts at 12 volts.-Models:...
s are built into the front or rear wheel hub, and are generally the most efficient; bottle dynamo
Bottle dynamo
A bottle dynamo or sidewall dynamo is a small electrical generator for bicycles employed to power a bicycle's lights — or to charge batteries for electronic devices including cellphones or GPS receivers....
s attach to the seatstay or fork and are rotated by a small wheel in contact with the tire sidewall, they are generally easiest to obtain and cheapest while European-designed tyres generally feature a raised "track" to run the generator's wheel; bottom bracket dynamos bolt between the chainstays behind the bottom bracket and are powered by a roller against the tyre, these are easy to fit and do not wear the tire sidewall. A fourth type is a spoke-mounted electromagnetic system.
Output and optics
Dynamos are generally limited to 0.5 A output, nominally 3 W at 6 V, although 12 V dynamos are available and the best nominal 6 V hub dynamos can produce 6 W at speed, as detailed here (a bottle dynamo is likely to slip if run at twice the nominal power, a hub dynamo does not have this problem). A dynamo behaves as a constant-current device, not constant voltage, so additional lamps added in series will draw the same current. However, this is only approximate, and the voltage can exceed the capacity of a single lamp at speed, causing failure. Historically this was a nuisance, but modern lamps and dynamos often incorporate Zener diodeZener diode
A Zener diode is a special kind of diode which allows current to flow in the forward direction in the same manner as an ideal diode, but will also permit it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "Zener knee voltage" or "Zener...
s to prevent it, and dynamos can be designed to "saturate" beyond a certain voltage to protect the lamp (saturation is a feature of all permanent magnet generators). Good dynamos can achieve efficiencies of up to 70% (i.e., under 5 W of the rider's output is diverted to produce 3 W of electricity) and provide full output at surprisingly low speeds, often 4 to 6 mph (6 to 10 km/h) is sufficient for full brightness.
To compensate for their limited output, dynamo headlights have good optics which focus the limited amount of light in a narrow beam that lights up the road directly in front of the bicycle; this can be seen in Andreas Oehler's side-by side comparison of beam patterns.
To produce light when the bike is stationary, some dynamo lights have a stand light facility, usually a single blue-white LED powered by a capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
, which runs for around five minutes. It is now common to use all the dynamo's output to power the front light; the alternative is a 2.4 W headlight and a 0.6 W tail light. Most good dynamo rear lights now use LEDs instead of incandescent lamps. Increasingly, dynamo headlights use LED light sources for the main beam as well as the standlight; some manufacturers include B&M, Supernova (both German) and Solidlights (British). In these newer lamps, the dynamo output requires substantial cleaning up and rectification by electronics before it can be used to drive an LED, whereas a conventional filament lamp will run happily on the "raw" AC from the dynamo.
Pros and cons
Hub dynamos are generally considered the best but require a wheel to be rebuilt if retrofitted (the existing rim can usually be reused). Some bikes are available with hub dynamo lighting systems as a factory option; this can be very cost-effective.Some riders consider the output of dynamo lighting insufficient. Others report that it is adequate to see on dark roads at speeds up to about 20 mph (32.19 km/h), (single 3 W) or more if a 12 V system is used. LED headlights typically give 2-3 times the light output of a halogen lamp for the same power, due to their greater efficiency.
Advantages of dynamo lighting
- Unlimited burn time
- Always available
- Reliable (see below for known issues with bottle dynamos)
- Environmentally friendly and inexpensive to run
- Unattractive to thieves, due to difficult removal, therefore the lights don't have to be removed by the user when parking the bicycle
Disadvantages
- Bottle dynamos may be noisy, can slip when wet, and may wear the sidewall of the tire
- Cut out at very low speeds (below walking pace); in particular no lighting available when stopped. Modern dynamos or lamps often add capacitors to keep the lights going for a short while when the bike slows or stops, or in-line rechargeable batteries for long-time use of unused real-time energy.
- Maximum power output obtainable is lower than with batteries
- Difficult to remove by the owner to thwart theft or vandalism
- Cheap or poorly aligned dynamos produce noticeable drag
- Old dynamos and lamps did not limit their output voltage, leading to early failure of the incandescent light bulbIncandescent light bulbThe incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
s in the lamps. Modern lamps and dynamos contain voltage limiters to solve this problem.
Magnetic lights
Many Danish bikes features lights powered through electromagnetic inductionElectromagnetic induction
Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, induction motors, electric motors, synchronous motors, and solenoids....
. The lights are mounted on the bike wheels, eliminating the need for batteries. The advantages are pretty much the same as with dynamo lighting while incurring less resistance to the rider than traditional dynamos and eliminating the noise and wear of the tire.
Supplementary lighting and conspicuity
Headtorches
Headtorches are a useful adjunct to bicycle lights. They can be pointed without steering the bike, giving useful "fill-in" lighting especially on poor or very dark roads. They also allow the wearer to read road and directional signs placed on high signposts.Some rechargeable systems offer a head torch option powered from the main battery pack.
Automatic turn signals worn on hand
In recent times, automatic turn indicators became available. They react to a change of orientation (an angle) in relation to Earth gravity; they blink only when a cyclist's hand is out-stretched to indicate a turn. One such product is incorporated into a cycling glove.LED Front and Rear turn signals
Light systems are starting to incorporate turn signals through wireless dashboards. They function on a ten second delay and return back to previous light mode. They only blink when wireless dashboard is pressed. A product that is using high powerd LEDs for turn indicators is seen here.Manually operated turn signals
Also in recent times, there have been manually operated signals that are available, usually having an LED tail light incorporated into the fixture, which contains the two signals found on the left and right respectively. An example can be found here.Reflective and high-visibility materials
Retro-reflective materialsRetroreflector
A retroreflector is a device or surface that reflects light back to its source with a minimum scattering of light. An electromagnetic wave front is reflected back along a vector that is parallel to but opposite in direction from the wave's source. The device or surface's angle of incidence is...
, in the form of reflectors, reflective tape, and reflective clothing, are useful in making a cyclist visible to other road users. Reflective materials can be applied to bike, rider, luggage, and tyres are available with reflective sidewalls.
On the bike
Reflectors and reflective tape provide additional visibility (especially when applied to moving parts of the bicycle) and are mandatory in many jurisdictions. Pedal reflectors in particular are very visible to following traffic as they move up and down; unfortunately they are not compatible with most clipless pedal systems, although adaptors are available for some, mainly older SPD models, and a few single-sided designs are available with built-in reflectors. In the UK, where front and rear pedal reflectors are compulsory after dark, most cyclists with clipless pedals are therefore riding illegally. The law is rarely, if ever, enforced, but could potentially be used in court to reduce financial compensation if the cyclist was hit by another vehicle. The CTCCyclists' Touring Club
CTC and the UK's national cyclists' organisation are the trading names of the Cyclists' Touring Club.CTC is the United Kingdom's largest cycling membership organisation. It also has member groups in the Republic of Ireland...
have suggested that the requirement could be waived if the cyclist fits an additional rear reflector and/or lighting, but this was not changed in the last revision of the UK vehicle lighting laws (which permitted flashing LEDs). Riders of recumbent bicycle
Recumbent bicycle
A recumbent bicycle is a bicycle that places the rider in a laid-back reclining position. Most recumbent riders choose this type of design for ergonomic reasons; the rider's weight is distributed comfortably over a larger area, supported by back and buttocks...
s have pointed out that the pedal reflector requirement is nonsensical for them, since the reflectors point straight up and down in use, and are invisible from other vehicles. As of 2008, California law allows white or yellow shoe reflectors (front and back), or reflective ankle bands, in lieu of pedal reflectors.
Reflectives are visible only when in the beam of a headlight, and even then only within a narrow locus. Importantly, they do nothing to light up the road. Reflectors are not a substitute for lights.
Clothing
Scotchlite
Scotchlite is a retroreflective material made by 3M. Its primary use is in nighttime high-visibility applications, such as 'reflective tape' for cyclists, safety vests for road workers, or the front of many traffic signs...
will show up boldly in car headlights. Evidence shows that bright material on the sleeves can prompt drivers to give more passing distance . Retroreflective materials can discourage some oncoming motorists from dipping their headlights, as the rider become less visible if they do.
The colour of lighting should be checked in the rider's area. A single solid colour can disappear under artificial light, particularly yellow sodium vapour lighting, and colour blindness is common; red/green colourblindness can make yellow fluorescent vanish against a green background (hedges or grass), although people with red/green colourblindness dispute this. Vests with both yellow and orange fluorescent plus wide strips of reflective may be the best solution.
In recent times electroluminescent
Electroluminescence
Electroluminescence is an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field...
clothing has become available to add to the existing array of LED-illuminated armbands and helmet blinkies. An electroluminescent
Electroluminescence
Electroluminescence is an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field...
helmet has been patented.
Measures of light output
Three units are used to measure light output. Manufacturers do not always quote the most appropriate figure—for example, watts are commonly quoted, but wattage alone is a poor measure since (a) it reports the consumption of power rather than the output of light, and (b) lamp optics will significantly impact the portion of the light which is delivered where it is needed, for example concentrated in a spot beam or dispersed as in running lights. CandelaCandela
The candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function . A common candle emits light with a luminous intensity of roughly one candela...
s, measuring the intensity
Luminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye...
of a beam, are more appropriate when the aim is to illuminate brightly a small spot, while lumen
Lumen (unit)
The lumen is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux...
s, measuring the entire production of light, are more relevant to the purposes of broad beams or non-directional running lights.
Watts
The watt (W) is the unit of powerPower (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
, and is usually quoted for the electrical power input, not the light power output. Electrical power is the product of voltage and current (watts = volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
s × ampere
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
s). Input power is only useful when comparing lights of similar technologies. A 3 W halogen dynamo headlight will light the road up about the same as a rechargeable light of around 7–10 W, but the rechargeable usually outputs much more light to the sides, which is useful on trails (although wide and narrow beam versions are available). A 3 W LED is somewhat brighter than a halogen lamp but generally less well focused. HID lights put out large amounts of light and are often quoted in terms like "80 W halogen equivalent".
Candelas
The candela (cd) is the SI unit of luminous intensityLuminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye...
, that is power per unit solid angle
Solid angle
The solid angle, Ω, is the two-dimensional angle in three-dimensional space that an object subtends at a point. It is a measure of how large that object appears to an observer looking from that point...
, weighted according to the sensitivity of the human eye to various colours of light. A typical candle
Candle
A candle is a solid block or cylinder of wax with an embedded wick, which is lit to provide light, and sometimes heat.Today, most candles are made from paraffin. Candles can also be made from beeswax, soy, other plant waxes, and tallow...
produces light with about 1 candela of luminous intensity. A lamp can produce higher luminous intensity either by producing more light, or by focusing it tighter. The luminous intensity of a light depends on many factors, including the colour of the light and the eye's sensitivity to that colour, the optics involved, reflector and lens. Despite its complexity, it is a more useful measure than watts, because it defines how much usable light is shed in a given place: a dynamo headlight designed for road use and focused for seeing the road makes more efficient use of the power of the lamp than lights using rotationally symmetrical optics.
Lumens
The lumen (lm) is the SI unit for luminous fluxLuminous flux
In photometry, luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of...
, the total amount of light emitted by a source, weighted according to the sensitivity of the human eye to various colours of light. Lumens per watt is a common measure of the efficiency of a light source. The luminous flux is of less value for bicycle lighting due to the importance of directionality. Luminous intensity is much more useful, but lumens per watt is a handy way to compare the output of otherwise similar lights.
External links
- Bike Current FAQ page
- Home Made HID Bicycle Light
- DIY daylight visible LED bike light
- DIY high power LED headlamp
- Bicycle Light Projects
- 3W Luxeon LED Bike Light
- Collection of DIY bike light resources
- The "Alieneye": Plans and instructions for a 5W LED homebuilt light
- "Red Giant" Home built LED tail light