Ramp meter
Encyclopedia
A ramp meter, ramp signal or metering light is a device, usually a basic traffic light
or a two-section signal (red and green only, no yellow) light together with a signal controller, that regulates the flow of traffic entering freeways according to current traffic conditions. It is the use of traffic signals at freeway on-ramps to manage the rate of automobiles entering the freeway. Ramp metering systems have proved to be successful in decreasing traffic and improving driver safety.
Ramp meters are claimed to reduce congestion (increase speed and volume) on freeways by reducing demand and by breaking up platoons of cars. Two variations of demand reduction are commonly cited; one being access rate, the other diversion.
Criticisms of ramp metering primarily centre on impacts to users nearer to the urban core, which are typically delayed by the ramp metering, as compared to often uncontrolled users approaching from further out along the system. Such considerations may raise questions of equity, as was prevalent with the Milwaukee system. In the longer-term, it is conceivable that population growth may be encouraged further from the urban core and discouraged nearer, potentially encouraging sprawl development
and increasing fuel usage. Additional concerns include queued traffic overflowing out of the ramps and onto other streets approaching the interchange. However some cities, like Atlanta, have fixed this by having the meters shut off temporarily to "flush out" the ramp once the traffic hits the streets. The meters then turn back on once the ramp has been cleared. Another concern is the increased pollutant emissions arising from the metered traffic and from the additional emissions from accelerating from a stop to freeway speeds (versus accelerating from street speeds to freeway speeds). However, if ramp meters are effectively preventing congestion on the freeway itself, there should be reduced emissions on the freeway due to less idling and braking/acceleration, which should offset the minor increase in emissions on the ramps.
es to skip the queue
and get directly on the highway. Meters often only operate in rush hour
periods. Some ramp meters have only one lane of traffic at the signal; others may have two or more lanes of traffic. Generally, meters with multiple lanes only give one lane the green light at a time. In one common configuration, each entrance lane has two signals; a red-yellow-green signal perched overhead over each lane (or mounted high on a pole for a single lane), and a two-phase lamp mounted low on a pole next to the stop line.
The overhead lights are for cars approaching the metering point; the low-mounted two-phase lights are intended to be used by the vehicle at the front of the queue. In normal operation of the ramp meters, only the red and green lamps are used. However, when ramp metering is about to be enabled, the overhead lamps may show flashing or solid yellow to warn drivers to prepare to stop. (Once ramp metering is turned on, there is no further need for the yellow lamp.) In California, some meters allow two or three cars to proceed on a green light. These meters use red-yellow-green signals on both the upper and lower mounts on the pole, and operate in a standard green-yellow-red fashion.
The sophistication and extent of a ramp metering system should be based on the amount of improvement desired, existing traffic conditions, installation costs, and the continuing resource requirements that are necessary to operate and maintain the system effectively. The simplest form of control is a fixed time operation. It performs the basic functions of breaking up platoons into single-vehicle entries and setting an upper limit on the flow rates that enter the freeway. Presence and passage detectors may be installed on the ramp to actuate and terminate the metering cycles, but the metering rate is based on average traffic conditions at a particular ramp at a particular time. This type of operation provides the benefits associated with accident reductions, but is not as effective in regulating freeway volumes because there is no input about mainline traffic. Pre-timed control can be implemented on any number of 15ramps, and is often implemented as an initial operating strategy until individual ramps can be incorporated into a traffic responsive system. The next level of control, traffic responsive, establishes metering rates based on actual freeway conditions. The local traffic responsive approach utilizes detectors and a micro-processor to determine the mainline flow in the immediate vicinity of the ramp and the ramp demand to select an appropriate metering rate. Traffic responsive control also permits ramp metering to be used to help manage demand when incidents occur on the freeway, i.e. reduce the metering rate at ramps upstream of the incident and increase the rate at ramps downstream. System-wide control is a form of traffic responsive control but operates on the basis of total freeway conditions. Centralized computer controlled systems can handle numerous ramps in a traffic responsive scheme and feature multiple control programs and overrides. Control strategies can also be distributed among individual ramps. A significant feature of system control is interconnection that permits the metering rate at any ramp to be influenced by conditions at other locations. Denver showed that this type of control has significant benefits when properly applied.’
System control need not be limited to the freeway and its ramps. The concept of integrated traffic control combines or coordinates freeway and arterial street control systems to operate on the basis of corridor wide traffic conditions. The potential advantages of integrated control include reduced installation and operating costs, corridor wide surveillance, better motorist information, and quicker and coordinated use of all of the control elements (meters, signals, signs, etc.) in response to real time traffic conditions. Simulation results from one study showed that, during an incident, coordination of arterial traffic signals and ramp meters can improve the traffic performance of a corridor.
The only existing integrated system in the U.S. is the INFORM project, but the concept is attracting considerable interest. Two cities, Seattle and Irvine, California, are in the process of implementing systems. Numerous other agencies are actively considering the integration of freeway and signal control systems. The initial efforts are primarily aimed at non-recurring situations where the signal timing can be modified in response to freeway incidents. Work is also underway, however, on corridor wide surveillance and adaptive control strategies.
) are installed in the road, both on the ramp and on the main road which measure and calculate the traffic flow, speed and occupancy levels. These are then used to alter the number of vehicles that can leave the ramp. The more congested the main carriageway the fewer vehicles are allowed to leave the ramp, this is effected by giving longer red times to the traffic signals.
Much research is currently being carried out into the most appropriate algorithms for controlling ramp meter signals. Some algorithms that are in use or have been evaluated are ALINEA
, demand control and fuzzy algorithms.
control. One version of the demand control algorithm is the RWS strategy used in the Netherlands. In this algorithm the number of vehicles that the signals allow off the ramp is calculated as the difference between the flow before the ramp and the pre-specified capacity of the road.
officer who would stop traffic on an entrance ramp and release vehicles one at a time at a predetermined rate, so that the objectives of safer and smoother merging onto the freeway traffic was easier without disrupting the mainline flows.
Ramp metering was first implemented in 1963 on the Eisenhower Expressway (Interstate 290
) in Chicago
by Adolf D. May. Since then ramp-meters have been systematically deployed in many urban areas including Los Angeles
; San Diego
; Sacramento
; the San Francisco Bay Area
; Fresno
; Seattle
; Denver
; Phoenix
; Las Vegas
; Salt Lake City
; Portland
; Minneapolis-St. Paul; Milwaukee
; Columbus
; Cincinnati
; Houston
; Atlanta
; Miami
; Washington, DC (only along Interstate 395
and Interstate 66
in Arlington County, Virginia
); Kansas City, Missouri
; and along the Queen Elizabeth Way
in Mississauga, Ontario
, Canada.
Ramp meters are commonplace in the New York City
, Los Angeles
, San Francisco
, Chicago
, Seattle, Phoenix
, Milwaukee
, Columbus
, and Minneapolis-St. Paul metropolitan areas, and they are also found in more than two dozen smaller metropolitan areas. In the New York City metro area, locals refer to ramp meters as "merge lights" and in Houston they're known as "flow signals."
Ramp meters have been withdrawn after initial introduction in several cities, including Dallas, San Antonio, and Austin
, Texas. Disused metering signals can still be found along some parkways surrounding New York City
and Detroit
, as well as on one ramp to Interstate 64
/U.S. Route 40
in St. Louis, MO, on the WB entrance ramp from McCausland Ave., which will be removed as part of the New I-64 project in winter 2008. Although deactivated shortly after they were added, ramp meters have been reactivated at select interchanges of Interstate 476
in suburban Philadelphia.
Ramp meters were installed along Interstate 435
in Overland Park, Kansas
and Kansas City, Missouri
in 2009, and are scheduled to go into effect on November 24, 2009.
Ramp meters in Mississauga, Ontario
are designed in such a way so that if the queue waiting to enter the QEW grows to the point where it may back up onto city streets, the meter is lifted and all traffic entering the highway is able to move freely without waiting for the meter. The meter goes back into service once the ramp queue is reduced to a reasonable level. While this method may increase congestion on the highway itself, it has the benefit of keeping city arterials free of stopped traffic waiting in queue. Ramp queues are usually quite short, lasting only 5–6 seconds on average before the driver may continue to the freeway.
and concluded that when the ramp meters were turned off freeway capacity decreased by 9%, travel times increased by 22%, freeway speeds dropped by 7% and crashes increased by 26%. However, ramp meters remain controversial, and the Minnesota
State Department of Transportation has developed new ramp control strategies. Fewer meters are activated during the course of a normal day than prior to the 2000 study, some meters have been removed, timing has been altered so that no driver waits more than four minutes in ramp queue, and vehicles are not allowed to back up onto city streets.
. However, these mainline meters have not yet been activated (as of September 2006). Beaverton, Oregon
has a mainline meter on the Cedar Hills Connector turning from Oregon Route 217 northbound to U.S. Route 26
eastbound. A mainline meter also exists on California State Route 125
southbound at its junction with Interstate 8 in La Mesa, California
.
'. By 2006 50 ramp meters were installed. This number increases by 4 to 5 each year.
(A57) as temporary solution for the increased traffic before the definitive solution (building of the Passante di Mestre).
, including: M4 Western Motorway (Wallgrove Road on-ramp); the M5 East motorway (Kingsgrove Road on-ramp); and the citywest Link to Anzac Bridge. Ramp metering is also used on freeways in Melbourne
, including the Eastern Freeway and the Monash Freeway
. Brisbane's Pacific Motorway
also uses Ramp metering on some on ramps. On most motorways, ramp metering is activated when sensors indicate that traffic is heavy, however, some motorways without sensors use time-based activation.
The recent M1 Upgrade in Melbourne has installed 62 ramp meters that are coordinated using the HERO suit of algorithms developed by Markos Papageorgiou and Associates from the Technical University of Crete
. The system has been built on the STREAMS platform and utilises the state-of-the-art ITS architecture. All the ramps can be linked when required to resolve motorway bottlenecks before they emerge. The results of a recent trial improved capacity by 9% over the previous fixed time ramp metering system, average speeds increased by 20kmh and traffic throughput at bottleneck locations can be reliably maintained around 2200 PCE per lane (note the M1 is major freight route to the Port of Melbourne and has a very high heavy articulated vehicle mix. The HERO system takes real time data every 20 seconds from the motorway, ramps and arterial road in order determine the best signal timing for the next 20 seconds. The data detection system comprises Sensys detectors in every freeway lane at 500m spacings with a minimum detectors at three locations on each ramp including the freeway entrance with the arterial road. The system also manages the arterial road interface with the freeway, balances ramp queues and delays across ramps, and is capable of managing bottlenecks 3–4 km downstream of a ramp entrance. The system is also supplemented by real time travel time information to key destinations and incident and congestion information displayed on specially designed full colour VMS on the approaches to the freeway entrance ramps. This information provides sufficient advice for motorists to determine whether or not to use the freeway during incidents etc. The system also provides dynamic ramp closure in the event of a major incident.
A useful handbook on the design of coordinated freeway ramp metering is obtained from the following link. VicRoads Managed Freeways - Freeway Ramp Signals Handbook
. It is progressively being installed on 61 Southern, Northern and North Western Motorway on-ramps due to thick merging behaviour on several on-ramps during peak times. It will also be installed on all of the links. Auckland's ramp signals feature an amber light to clarify that normal traffic signal rules apply. Drivers failing to obey a red ramp signal will be ticketed and fined as if they had violated a normal red traffic light.
The majority of motorway on-ramps which did not already feature two-lane merging are being extended to allow for two lanes to the ramp signal stop line, to reduce on-ramp queue congestion (for example, Panmure on-ramp northbound). Where two lanes apply, one vehicle per lane is released per green signal. Due to their constrained design, other on-ramps remain one-lane only despite being ramp-signalled (e.g. Symonds Street on-ramp southbound).
Electronic message boards indicate whether ramp signals apply. The first board will display "RAMP SIGNAL ON" when ramp signals are activated, and the second board (closer to the on-ramp) "PREPARE TO STOP". Where ramp signals are switched off, the first board is blank and the second board displays "RAMP SIGNAL OFF".
Signals in Auckland have found a 30 km/h average speed increase while Ramp Signals are running, and are allowing 600-650 more vehicles through motorway sections.
and Pretoria
.
Has also been installed on the north bound on ramp from Blue Lagoon to the M4 Highway in Durban since early 2007
at Taipei Interchange from northbound Chongqing North Road to southbound National Highway No. 1
in northern Datong District, Taipei allows buses and properly indicated emergency vehicles to bypass the traffic control imposed by the ramp meters.
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...
or a two-section signal (red and green only, no yellow) light together with a signal controller, that regulates the flow of traffic entering freeways according to current traffic conditions. It is the use of traffic signals at freeway on-ramps to manage the rate of automobiles entering the freeway. Ramp metering systems have proved to be successful in decreasing traffic and improving driver safety.
Ramp meters are claimed to reduce congestion (increase speed and volume) on freeways by reducing demand and by breaking up platoons of cars. Two variations of demand reduction are commonly cited; one being access rate, the other diversion.
Impacts
Ramp meters are installed to restrict the total flow entering the freeway, temporarily storing it on the ramps, a process called "access rate reduction." In this way, the traffic flow does not exceed the freeway's capacity. Another rationale for installing ramp meters is the argument that they prevent congestion and break up "platoons" of cars. A platoon is a group of vehicles travelling in proximity, such as a group released by an arterial traffic signal changing from red to green. Advocates of ramp meters claim that they break up platoons of vehicles entering freeways, ensuring that traffic can merge more easily. Another premise of ramp meters is diversion. The delay caused by the ramp meter waiting period may cause some drivers to choose other routes thereby reducing demand for the freeway.Criticisms of ramp metering primarily centre on impacts to users nearer to the urban core, which are typically delayed by the ramp metering, as compared to often uncontrolled users approaching from further out along the system. Such considerations may raise questions of equity, as was prevalent with the Milwaukee system. In the longer-term, it is conceivable that population growth may be encouraged further from the urban core and discouraged nearer, potentially encouraging sprawl development
Urban sprawl
Urban sprawl, also known as suburban sprawl, is a multifaceted concept, which includes the spreading outwards of a city and its suburbs to its outskirts to low-density and auto-dependent development on rural land, high segregation of uses Urban sprawl, also known as suburban sprawl, is a...
and increasing fuel usage. Additional concerns include queued traffic overflowing out of the ramps and onto other streets approaching the interchange. However some cities, like Atlanta, have fixed this by having the meters shut off temporarily to "flush out" the ramp once the traffic hits the streets. The meters then turn back on once the ramp has been cleared. Another concern is the increased pollutant emissions arising from the metered traffic and from the additional emissions from accelerating from a stop to freeway speeds (versus accelerating from street speeds to freeway speeds). However, if ramp meters are effectively preventing congestion on the freeway itself, there should be reduced emissions on the freeway due to less idling and braking/acceleration, which should offset the minor increase in emissions on the ramps.
Types
Some metered ramps have bypass lanes for high-occupancy vehicles, allowing carpoolers and busBus
A bus is a road vehicle designed to carry passengers. Buses can have a capacity as high as 300 passengers. The most common type of bus is the single-decker bus, with larger loads carried by double-decker buses and articulated buses, and smaller loads carried by midibuses and minibuses; coaches are...
es to skip the queue
Queue area
Queue areas are places in which people queue for goods or services. Examples include checking out groceries or other goods that have been collected in a self service shop, in a shop without self service, at an ATM, at a ticket desk, a city bus, or in a taxi stand.Queueing is a phenomenon in a...
and get directly on the highway. Meters often only operate in rush hour
Rush hour
A rush hour or peak hour is a part of the day during which traffic congestion on roads and crowding on public transport is at its highest. Normally, this happens twice a day—once in the morning and once in the evening, the times during when the most people commute...
periods. Some ramp meters have only one lane of traffic at the signal; others may have two or more lanes of traffic. Generally, meters with multiple lanes only give one lane the green light at a time. In one common configuration, each entrance lane has two signals; a red-yellow-green signal perched overhead over each lane (or mounted high on a pole for a single lane), and a two-phase lamp mounted low on a pole next to the stop line.
The overhead lights are for cars approaching the metering point; the low-mounted two-phase lights are intended to be used by the vehicle at the front of the queue. In normal operation of the ramp meters, only the red and green lamps are used. However, when ramp metering is about to be enabled, the overhead lamps may show flashing or solid yellow to warn drivers to prepare to stop. (Once ramp metering is turned on, there is no further need for the yellow lamp.) In California, some meters allow two or three cars to proceed on a green light. These meters use red-yellow-green signals on both the upper and lower mounts on the pole, and operate in a standard green-yellow-red fashion.
The sophistication and extent of a ramp metering system should be based on the amount of improvement desired, existing traffic conditions, installation costs, and the continuing resource requirements that are necessary to operate and maintain the system effectively. The simplest form of control is a fixed time operation. It performs the basic functions of breaking up platoons into single-vehicle entries and setting an upper limit on the flow rates that enter the freeway. Presence and passage detectors may be installed on the ramp to actuate and terminate the metering cycles, but the metering rate is based on average traffic conditions at a particular ramp at a particular time. This type of operation provides the benefits associated with accident reductions, but is not as effective in regulating freeway volumes because there is no input about mainline traffic. Pre-timed control can be implemented on any number of 15ramps, and is often implemented as an initial operating strategy until individual ramps can be incorporated into a traffic responsive system. The next level of control, traffic responsive, establishes metering rates based on actual freeway conditions. The local traffic responsive approach utilizes detectors and a micro-processor to determine the mainline flow in the immediate vicinity of the ramp and the ramp demand to select an appropriate metering rate. Traffic responsive control also permits ramp metering to be used to help manage demand when incidents occur on the freeway, i.e. reduce the metering rate at ramps upstream of the incident and increase the rate at ramps downstream. System-wide control is a form of traffic responsive control but operates on the basis of total freeway conditions. Centralized computer controlled systems can handle numerous ramps in a traffic responsive scheme and feature multiple control programs and overrides. Control strategies can also be distributed among individual ramps. A significant feature of system control is interconnection that permits the metering rate at any ramp to be influenced by conditions at other locations. Denver showed that this type of control has significant benefits when properly applied.’
System control need not be limited to the freeway and its ramps. The concept of integrated traffic control combines or coordinates freeway and arterial street control systems to operate on the basis of corridor wide traffic conditions. The potential advantages of integrated control include reduced installation and operating costs, corridor wide surveillance, better motorist information, and quicker and coordinated use of all of the control elements (meters, signals, signs, etc.) in response to real time traffic conditions. Simulation results from one study showed that, during an incident, coordination of arterial traffic signals and ramp meters can improve the traffic performance of a corridor.
The only existing integrated system in the U.S. is the INFORM project, but the concept is attracting considerable interest. Two cities, Seattle and Irvine, California, are in the process of implementing systems. Numerous other agencies are actively considering the integration of freeway and signal control systems. The initial efforts are primarily aimed at non-recurring situations where the signal timing can be modified in response to freeway incidents. Work is also underway, however, on corridor wide surveillance and adaptive control strategies.
Ramp metering signal controls
Ramp meter signals are set according to the current traffic conditions on the road. Detectors (generally an induction loopInduction loop
Induction loop is a term used to describe an electromagnetic communication- and detection system, relying on the fact that a moving magnet will induce an electrical current in a nearby conducting wire. Induction loops are used for transmission and reception of communication signals, or for...
) are installed in the road, both on the ramp and on the main road which measure and calculate the traffic flow, speed and occupancy levels. These are then used to alter the number of vehicles that can leave the ramp. The more congested the main carriageway the fewer vehicles are allowed to leave the ramp, this is effected by giving longer red times to the traffic signals.
Much research is currently being carried out into the most appropriate algorithms for controlling ramp meter signals. Some algorithms that are in use or have been evaluated are ALINEA
Alinea
Alinea may refer to:• Alinea, a restaurant in Chicago by chef Grant Achatz • Alinea, from the Latin a linea, referring to the pilcrow which indicates a new paragraph...
, demand control and fuzzy algorithms.
Demand control algorithms
The demand control algorithms are examples of feed-forwardFeed-forward
Feed-forward is a term describing an element or pathway within a control system which passes a controlling signal from a source in the control system's external environment, often a command signal from an external operator, to a load elsewhere in its external environment...
control. One version of the demand control algorithm is the RWS strategy used in the Netherlands. In this algorithm the number of vehicles that the signals allow off the ramp is calculated as the difference between the flow before the ramp and the pre-specified capacity of the road.
Ramp metering in North America
This first application involved a 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...
officer who would stop traffic on an entrance ramp and release vehicles one at a time at a predetermined rate, so that the objectives of safer and smoother merging onto the freeway traffic was easier without disrupting the mainline flows.
Ramp metering was first implemented in 1963 on the Eisenhower Expressway (Interstate 290
Interstate 290 (Illinois)
Interstate 290 is a main Interstate freeway that runs westwards from the Chicago Loop. A portion of I-290 is officially called the Dwight D. Eisenhower Expressway. In short form, it is known as "the Ike" or the Eisenhower...
) in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
by Adolf D. May. Since then ramp-meters have been systematically deployed in many urban areas including Los Angeles
Los Angeles County, California
Los Angeles County is a county in the U.S. state of California. As of 2010 U.S. Census, the county had a population of 9,818,605, making it the most populous county in the United States. Los Angeles County alone is more populous than 42 individual U.S. states...
; San Diego
San Diego, California
San Diego is the eighth-largest city in the United States and second-largest city in California. The city is located on the coast of the Pacific Ocean in Southern California, immediately adjacent to the Mexican border. The birthplace of California, San Diego is known for its mild year-round...
; Sacramento
Sacramento, California
Sacramento is the capital city of the U.S. state of California and the county seat of Sacramento County. It is located at the confluence of the Sacramento River and the American River in the northern portion of California's expansive Central Valley. With a population of 466,488 at the 2010 census,...
; the San Francisco Bay Area
San Francisco Bay Area
The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...
; Fresno
Fresno, California
Fresno is a city in central California, United States, the county seat of Fresno County. As of the 2010 census, the city's population was 510,365, making it the fifth largest city in California, the largest inland city in California, and the 34th largest in the nation...
; Seattle
Seattle, Washington
Seattle is the county seat of King County, Washington. With 608,660 residents as of the 2010 Census, Seattle is the largest city in the Northwestern United States. The Seattle metropolitan area of about 3.4 million inhabitants is the 15th largest metropolitan area in the country...
; Denver
Denver, Colorado
The City and County of Denver is the capital and the most populous city of the U.S. state of Colorado. Denver is a consolidated city-county, located in the South Platte River Valley on the western edge of the High Plains just east of the Front Range of the Rocky Mountains...
; Phoenix
Phoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
; Las Vegas
Las Vegas metropolitan area
The Las Vegas Valley is the heart of the Las Vegas-Paradise, NV MSA also known as the Las Vegas–Paradise–Henderson MSA which includes all of Clark County, Nevada, and is a metropolitan area in the southern part of the U.S. state of Nevada. The Valley is defined by the Las Vegas Valley landform, a ...
; Salt Lake City
Salt Lake City, Utah
Salt Lake City is the capital and the most populous city of the U.S. state of Utah. The name of the city is often shortened to Salt Lake or SLC. With a population of 186,440 as of the 2010 Census, the city lies in the Salt Lake City metropolitan area, which has a total population of 1,124,197...
; Portland
Portland, Oregon
Portland is a city located in the Pacific Northwest, near the confluence of the Willamette and Columbia rivers in the U.S. state of Oregon. As of the 2010 Census, it had a population of 583,776, making it the 29th most populous city in the United States...
; Minneapolis-St. Paul; Milwaukee
Milwaukee, Wisconsin
Milwaukee is the largest city in the U.S. state of Wisconsin, the 28th most populous city in the United States and 39th most populous region in the United States. It is the county seat of Milwaukee County and is located on the southwestern shore of Lake Michigan. According to 2010 census data, the...
; Columbus
Columbus, Ohio
Columbus is the capital of and the largest city in the U.S. state of Ohio. The broader metropolitan area encompasses several counties and is the third largest in Ohio behind those of Cleveland and Cincinnati. Columbus is the third largest city in the American Midwest, and the fifteenth largest city...
; Cincinnati
Cincinnati, Ohio
Cincinnati is a city in the U.S. state of Ohio. Cincinnati is the county seat of Hamilton County. Settled in 1788, the city is located to north of the Ohio River at the Ohio-Kentucky border, near Indiana. The population within city limits is 296,943 according to the 2010 census, making it Ohio's...
; Houston
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...
; Atlanta
Atlanta, Georgia
Atlanta is the capital and most populous city in the U.S. state of Georgia. According to the 2010 census, Atlanta's population is 420,003. Atlanta is the cultural and economic center of the Atlanta metropolitan area, which is home to 5,268,860 people and is the ninth largest metropolitan area in...
; Miami
Miami, Florida
Miami is a city located on the Atlantic coast in southeastern Florida and the county seat of Miami-Dade County, the most populous county in Florida and the eighth-most populous county in the United States with a population of 2,500,625...
; Washington, DC (only along Interstate 395
Interstate 395 (District of Columbia-Virginia)
Interstate 395 in Washington, D.C., and Virginia is a 13 mile long spur route that begins at a junction with Interstate 95 in Springfield, Virginia and ends in northwest Washington, D.C. It passes underneath the National Mall near the United States Capitol and ends at a junction with U.S...
and Interstate 66
Interstate 66
Interstate 66 is an Interstate Highway in the eastern United States. As indicated by its even route number, it runs in an east–west direction. Its western terminus is at Middletown, Virginia, at an intersection with Interstate 81; its eastern terminus is in Washington, D.C., at an...
in Arlington County, Virginia
Arlington County, Virginia
Arlington County is a county in the Commonwealth of Virginia. The land that became Arlington was originally donated by Virginia to the United States government to form part of the new federal capital district. On February 27, 1801, the United States Congress organized the area as a subdivision of...
); Kansas City, Missouri
Kansas City, Missouri
Kansas City, Missouri is the largest city in the U.S. state of Missouri and is the anchor city of the Kansas City Metropolitan Area, the second largest metropolitan area in Missouri. It encompasses in parts of Jackson, Clay, Cass, and Platte counties...
; and along the Queen Elizabeth Way
Queen Elizabeth Way
The Queen Elizabeth Way, commonly abbreviated as the QEW, is a 400-Series highway in the Canadian province of Ontario. The freeway links Buffalo, New York and the Niagara Peninsula with Toronto. It begins at the Peace Bridge in Fort Erie and travels around the western shore of Lake Ontario, ending...
in Mississauga, Ontario
Mississauga, Ontario
Mississauga is a city in Southern Ontario located in the Regional Municipality of Peel, and in the western part of the Greater Toronto Area. With an estimated population of 734,000, it is Canada's sixth-most populous municipality, and has almost doubled in population in each of the last two decades...
, Canada.
Ramp meters are commonplace in the New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
, Los Angeles
Los Angeles, California
Los Angeles , with a population at the 2010 United States Census of 3,792,621, is the most populous city in California, USA and the second most populous in the United States, after New York City. It has an area of , and is located in Southern California...
, San Francisco
San Francisco, California
San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...
, Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
, Seattle, Phoenix
Phoenix, Arizona
Phoenix is the capital, and largest city, of the U.S. state of Arizona, as well as the sixth most populated city in the United States. Phoenix is home to 1,445,632 people according to the official 2010 U.S. Census Bureau data...
, Milwaukee
Milwaukee, Wisconsin
Milwaukee is the largest city in the U.S. state of Wisconsin, the 28th most populous city in the United States and 39th most populous region in the United States. It is the county seat of Milwaukee County and is located on the southwestern shore of Lake Michigan. According to 2010 census data, the...
, Columbus
Columbus, Ohio
Columbus is the capital of and the largest city in the U.S. state of Ohio. The broader metropolitan area encompasses several counties and is the third largest in Ohio behind those of Cleveland and Cincinnati. Columbus is the third largest city in the American Midwest, and the fifteenth largest city...
, and Minneapolis-St. Paul metropolitan areas, and they are also found in more than two dozen smaller metropolitan areas. In the New York City metro area, locals refer to ramp meters as "merge lights" and in Houston they're known as "flow signals."
Ramp meters have been withdrawn after initial introduction in several cities, including Dallas, San Antonio, and Austin
Austin
Austin is the capital of the U.S. state of Texas.Austin may also refer to:-In the United States:*Austin, Arkansas*Austin, Colorado*Austin, Chicago, Illinois*Austin, Indiana*Austin, Minnesota*Austin, Nevada*Austin, Oregon...
, Texas. Disused metering signals can still be found along some parkways surrounding New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...
and Detroit
Detroit, Michigan
Detroit is the major city among the primary cultural, financial, and transportation centers in the Metro Detroit area, a region of 5.2 million people. As the seat of Wayne County, the city of Detroit is the largest city in the U.S. state of Michigan and serves as a major port on the Detroit River...
, as well as on one ramp to Interstate 64
Interstate 64
Interstate 64 is an Interstate Highway in the Midwestern and Southeastern United States. Its western terminus is at I-70, U.S. 40, and U.S. 61 in Wentzville, Missouri. Its eastern terminus is at an interchange with I-264 and I-664 at Bowers Hill in Chesapeake, Virginia. As I-64 is concurrent with...
/U.S. Route 40
U.S. Route 40
U.S. Route 40 is an east–west United States highway. As with most routes whose numbers end in a zero, U.S. 40 once traversed the entire United States. It is one of the original 1920s U.S. Highways, and its first termini were San Francisco, California, and Atlantic City, New Jersey...
in St. Louis, MO, on the WB entrance ramp from McCausland Ave., which will be removed as part of the New I-64 project in winter 2008. Although deactivated shortly after they were added, ramp meters have been reactivated at select interchanges of Interstate 476
Interstate 476
Interstate 476 is a auxiliary Interstate Highway in the U.S. state of Pennsylvania designated between Interstate 95 near Chester and Interstate 81 near Scranton, serving as the primary north–south Interstate corridor through eastern Pennsylvania....
in suburban Philadelphia.
Ramp meters were installed along Interstate 435
Interstate 435
Interstate 435 is an Interstate Highway beltway that encircles much of the Kansas City, Missouri Metropolitan Area in the states of Kansas and Missouri, USA.- Route description :...
in Overland Park, Kansas
Overland Park, Kansas
-Demographics:As of the census of 2000, there were 149,080 people, 59,703 households, and 39,702 families residing in the city. The population density was 2,627.0 people per square mile . There were 62,586 housing units at an average density of 1,102.9 per square mile...
and Kansas City, Missouri
Kansas City, Missouri
Kansas City, Missouri is the largest city in the U.S. state of Missouri and is the anchor city of the Kansas City Metropolitan Area, the second largest metropolitan area in Missouri. It encompasses in parts of Jackson, Clay, Cass, and Platte counties...
in 2009, and are scheduled to go into effect on November 24, 2009.
Ramp meters in Mississauga, Ontario
Mississauga, Ontario
Mississauga is a city in Southern Ontario located in the Regional Municipality of Peel, and in the western part of the Greater Toronto Area. With an estimated population of 734,000, it is Canada's sixth-most populous municipality, and has almost doubled in population in each of the last two decades...
are designed in such a way so that if the queue waiting to enter the QEW grows to the point where it may back up onto city streets, the meter is lifted and all traffic entering the highway is able to move freely without waiting for the meter. The meter goes back into service once the ramp queue is reduced to a reasonable level. While this method may increase congestion on the highway itself, it has the benefit of keeping city arterials free of stopped traffic waiting in queue. Ramp queues are usually quite short, lasting only 5–6 seconds on average before the driver may continue to the freeway.
Minneapolis-Saint Paul ramp meter experiment
In 2000, a $650,000 experiment was mandated by the Minnesota State Legislature in response to citizen complaints and the efforts of State Senator Dick Day http://www.senate.leg.state.mn.us/members/member_bio.php?district=26. The study involved shutting off all 433 ramp meters in the Minneapolis-St. Paul area for eight weeks to test their effectiveness. The study was conducted by Cambridge SystematicsCambridge Systematics
Cambridge Systematics is a company that was founded in 1972 by four Massachusetts Institute of Technology professors and a transportation consultant in Cambridge, Massachusetts...
and concluded that when the ramp meters were turned off freeway capacity decreased by 9%, travel times increased by 22%, freeway speeds dropped by 7% and crashes increased by 26%. However, ramp meters remain controversial, and the Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...
State Department of Transportation has developed new ramp control strategies. Fewer meters are activated during the course of a normal day than prior to the 2000 study, some meters have been removed, timing has been altered so that no driver waits more than four minutes in ramp queue, and vehicles are not allowed to back up onto city streets.
Mainline metering
A mainline meter throttles traffic flow from one segment of a highway to the next by directly metering the highway's traffic. Such a scheme is typically implemented in specialized situations such as bridges and tunnels. A mainline meter was installed at the San Francisco – Oakland Bay Bridge toll plaza in the early 1970s. Similar mainline meters have also been installed downstream from the toll plazas at two other San Francisco Bay crossings, the San Mateo Bridge and the Dumbarton BridgeDumbarton Bridge (California)
The Dumbarton Bridge is the southernmost of the highway bridges that span the San Francisco Bay in California. Carrying over 81,000 vehicles daily, it is also the shortest bridge across San Francisco Bay at 1.63 miles...
. However, these mainline meters have not yet been activated (as of September 2006). Beaverton, Oregon
Beaverton, Oregon
Beaverton is a city in Washington County, Oregon, United States, seven miles west of Portland in the Tualatin River Valley.As of the 2010 census, the population is 90,267. This makes it the second-largest city in the county and Oregon's sixth-largest city...
has a mainline meter on the Cedar Hills Connector turning from Oregon Route 217 northbound to U.S. Route 26
U.S. Route 26
U.S. Route 26 is an east–west United States highway. It started in Ogallala, Nebraska, and gradually grew to reach the West Coast in Oregon. When the U.S. highway system was first defined, it was limited to Nebraska and Wyoming; by the 1950s, it continued into Idaho and Oregon. The...
eastbound. A mainline meter also exists on California State Route 125
California State Route 125
State Route 125 is a state highway in the U.S. state of California that currently runs from State Route 905 in Otay Mesa near the U.S.–Mexico border to State Route 52 in Santee....
southbound at its junction with Interstate 8 in La Mesa, California
La Mesa, California
La Mesa is a city in San Diego County, California. The population was 57,065 at the 2010 census, up from 54,749 at the 2000 census. It was founded in 1869 and officially incorporated as a city on February 16, 1912. Its official flower is the bougainvillea....
.
Ramp metering in Europe
Ramp metering has been installed in several countries in Europe, including the United Kingdom, Germany and the Netherlands. A research project Euramp on ramp metering funded by the European Union is due for completion in March 2007.United Kingdom
The first trial in the UK was on the M6 J10 near Walsall in 1986. No more sites were developed for the next two decades until a second 'pilot' study in 2006 by the Highways Agency (HA) concluded that ramp metering provides a net benefit under certain conditions - generally more congested junctions. Ramp metering was then introduced widely in England - Phase 1 involved the implementation of approximately 30 sites and was completed by 2008. Phase 2 followed and as of March 2011 there are 88 Ramp Metering sites on the 4,500 miles of strategic highways operated and maintained by the HA.The Netherlands
The first ramp metering in the Netherlands was introduced in 1989. Ramp metering is being introduced more widely in the Netherlands after a pilot study by the AVV Transport Research Centre which concluded that ramp metering can provide a small benefit for the traffic flow on the highway, leading to a higher capacity. Ramp meters can also contribute to decreasing 'rat runningRat run
Rat running or cut-through driving refers to the use of secondary roads or residential side streets instead of the intended main roads in urban or suburban areas. People do it to avoid heavy traffic, lengthy traffic signals or other obstacles, even where there are traffic calming measures to...
'. By 2006 50 ramp meters were installed. This number increases by 4 to 5 each year.
Germany
Ramp metering has been implemented on Autobahns in several areas in Germany, including the Rhine-Ruhr area, Munich, and Hamburg.Italy
Ramp metering has been implemented on Tangenziale di VeneziaTangenziale di Venezia
The Tangenziale di Mestre , or Autostrada A57, was opened to traffic on 3 September 1972 in northern Italy.-Overview:The oOriginal design was to have this central dual carriageway to serve as the Autostrada A4 , and by each side another separated single carriageway to serve as local beltway : but,...
(A57) as temporary solution for the increased traffic before the definitive solution (building of the Passante di Mestre).
Japan
Ramp metering is being installed in Japan in the next few years to keep the flow of traffic moving in Japan. There are plans to install ramp meters on every on-ramp in the Japan motorway system.Australia
Ramp metering is used to regulate access to a number of major roads in SydneySydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...
, including: M4 Western Motorway (Wallgrove Road on-ramp); the M5 East motorway (Kingsgrove Road on-ramp); and the citywest Link to Anzac Bridge. Ramp metering is also used on freeways in Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
, including the Eastern Freeway and the Monash Freeway
Monash Freeway
Monash Freeway is an urban freeway in Victoria, Australia linking Melbourne's CBD to its southeastern suburbs and the Gippsland region. The entire stretch of the Monash Freeway bears the designation...
. Brisbane's Pacific Motorway
Pacific Motorway
The Pacific Motorway is a 100 km long motorway in Australia between Brisbane, Queensland, and the New South Wales-Queensland border at Tweed Heads. The motorway starts at Coronation Drive at Milton in Brisbane, and from 2008 links the Tweed Heads bypass in New South Wales...
also uses Ramp metering on some on ramps. On most motorways, ramp metering is activated when sensors indicate that traffic is heavy, however, some motorways without sensors use time-based activation.
The recent M1 Upgrade in Melbourne has installed 62 ramp meters that are coordinated using the HERO suit of algorithms developed by Markos Papageorgiou and Associates from the Technical University of Crete
Technical University of Crete
The Technical University of Crete is a state university under the supervision of the Greek Ministry of Education and was founded in 1977 in Chania, Crete. The first students were admitted in 1984. The campus is located on a panoramic site in the peninsula of Akrotiri and covers an area of ,...
. The system has been built on the STREAMS platform and utilises the state-of-the-art ITS architecture. All the ramps can be linked when required to resolve motorway bottlenecks before they emerge. The results of a recent trial improved capacity by 9% over the previous fixed time ramp metering system, average speeds increased by 20kmh and traffic throughput at bottleneck locations can be reliably maintained around 2200 PCE per lane (note the M1 is major freight route to the Port of Melbourne and has a very high heavy articulated vehicle mix. The HERO system takes real time data every 20 seconds from the motorway, ramps and arterial road in order determine the best signal timing for the next 20 seconds. The data detection system comprises Sensys detectors in every freeway lane at 500m spacings with a minimum detectors at three locations on each ramp including the freeway entrance with the arterial road. The system also manages the arterial road interface with the freeway, balances ramp queues and delays across ramps, and is capable of managing bottlenecks 3–4 km downstream of a ramp entrance. The system is also supplemented by real time travel time information to key destinations and incident and congestion information displayed on specially designed full colour VMS on the approaches to the freeway entrance ramps. This information provides sufficient advice for motorists to determine whether or not to use the freeway during incidents etc. The system also provides dynamic ramp closure in the event of a major incident.
A useful handbook on the design of coordinated freeway ramp metering is obtained from the following link. VicRoads Managed Freeways - Freeway Ramp Signals Handbook
New Zealand
Ramp metering is being installed Auckland-wide after a successful trial on Mahunga Drive, before the Mangere BridgeMangere Bridge
Mangere Bridge, officially also called the Manukau Harbour Crossing, is a motorway bridge over the Manukau Harbour in south-western Auckland, New Zealand, crossing between the suburb also known as Mangere Bridge and the suburb of Onehunga...
. It is progressively being installed on 61 Southern, Northern and North Western Motorway on-ramps due to thick merging behaviour on several on-ramps during peak times. It will also be installed on all of the links. Auckland's ramp signals feature an amber light to clarify that normal traffic signal rules apply. Drivers failing to obey a red ramp signal will be ticketed and fined as if they had violated a normal red traffic light.
The majority of motorway on-ramps which did not already feature two-lane merging are being extended to allow for two lanes to the ramp signal stop line, to reduce on-ramp queue congestion (for example, Panmure on-ramp northbound). Where two lanes apply, one vehicle per lane is released per green signal. Due to their constrained design, other on-ramps remain one-lane only despite being ramp-signalled (e.g. Symonds Street on-ramp southbound).
Electronic message boards indicate whether ramp signals apply. The first board will display "RAMP SIGNAL ON" when ramp signals are activated, and the second board (closer to the on-ramp) "PREPARE TO STOP". Where ramp signals are switched off, the first board is blank and the second board displays "RAMP SIGNAL OFF".
Signals in Auckland have found a 30 km/h average speed increase while Ramp Signals are running, and are allowing 600-650 more vehicles through motorway sections.
South Africa
Ramp meters were, for a while, installed on the Samrand South bound, Old Johannesburg South bound and on New Road North and South bound interchanges on the N1 Ben Schoeman highway. The ramp metering was part of the Intelligent Transport System launched in October 2007 to aid traffic flow between JohannesburgJohannesburg
Johannesburg also known as Jozi, Jo'burg or Egoli, is the largest city in South Africa, by population. Johannesburg is the provincial capital of Gauteng, the wealthiest province in South Africa, having the largest economy of any metropolitan region in Sub-Saharan Africa...
and Pretoria
Pretoria
Pretoria is a city located in the northern part of Gauteng Province, South Africa. It is one of the country's three capital cities, serving as the executive and de facto national capital; the others are Cape Town, the legislative capital, and Bloemfontein, the judicial capital.Pretoria is...
.
Has also been installed on the north bound on ramp from Blue Lagoon to the M4 Highway in Durban since early 2007
Taiwan
Freeways in Taiwan use ramp meters during peak hours since 1993. Traffic enforcement cameras are deployed to deter running the red lights, but a bus laneBus lane
A bus lane or bus only lane is a lane restricted to buses, and generally used to speed up public transport that would be otherwise held up by traffic congestion...
at Taipei Interchange from northbound Chongqing North Road to southbound National Highway No. 1
National Highway No. 1 (Taiwan)
National Highway No. 1 is the first freeway in Taiwan. It begins in Keelung City at the intersection of Ziao 2nd Road and Jhong 4th Road and ends in Kaohsiung City at the intersection of Jhongshan 4th Road and Yugang Road, giving it a total length of 372.8 km...
in northern Datong District, Taipei allows buses and properly indicated emergency vehicles to bypass the traffic control imposed by the ramp meters.
See also
External links
- M5 Merge Safe (RTA)
- University of Minnesota
- Ramp Signalling - Auckland Ramp Signalling information
- Ramp Meters in the U.S.