Traffic engineering (transportation)
Encyclopedia
For the engineering of communications and computer networks, see Teletraffic engineering
.
Traffic engineering is a branch of civil engineering
that uses engineering
techniques to achieve the safe and efficient movement of people and goods on roadways. It focuses mainly on research and construction of the infrastructure necessary for safe and efficient traffic flow
, such as road
geometry, sidewalks and crosswalks, segregated cycle facilities
, shared lane marking
, traffic signs, road surface marking
s and traffic lights.
Traffic engineering is closely associated with other disciplines:
Typical traffic engineering projects involve designing traffic control device installations and modifications, including traffic signals, signs, and pavement markings. However, traffic engineers also consider traffic safety by investigating locations with high crash rates and developing countermeasures to reduce crashes. Traffic flow management can be short-term (preparing construction traffic control plans, including detour plans for pedestrian and vehicular traffic) or long-term (estimating the impacts of proposed commercial developments on traffic patterns). Increasingly, traffic problems are being addressed by developing systems for intelligent transportation systems, often in conjunction with other engineering disciplines, such as computer engineering
and electrical engineering
.
Observation on limited access facilities suggests that up to a maximum flow, speed does not decline while density increases. However, above a critical threshold, increased density reduces speed. Additionally, beyond a further threshold, increased density reduces flow as well.
Therefore, speeds and lane flows at bottlenecks can be kept high during peak periods by managing traffic density using devices that limit the rate at which vehicles can enter the highway. Ramp meter
s, signals on entrance ramps that control the rate at which vehicles are allowed to enter the mainline facility, provide this function (at the expense of increased delay for those waiting at the ramps).
A typical traffic safety investigation follows these steps
Teletraffic engineering
Telecommunications traffic engineering, teletraffic engineering, or traffic engineering is the application of traffic engineering theory to telecommunications...
.
Civil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...
that uses engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
techniques to achieve the safe and efficient movement of people and goods on roadways. It focuses mainly on research and construction of the infrastructure necessary for safe and efficient traffic flow
Traffic flow
Traffic flow, in mathematics and civil engineering, is the study of interactions between vehicles, drivers, and infrastructure , with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems.-History:Attempts to...
, such as road
Road
A road is a thoroughfare, route, or way on land between two places, which typically has been paved or otherwise improved to allow travel by some conveyance, including a horse, cart, or motor vehicle. Roads consist of one, or sometimes two, roadways each with one or more lanes and also any...
geometry, sidewalks and crosswalks, segregated cycle facilities
Segregated cycle facilities
Segregated cycle facilities are marked lanes, tracks, shoulders and paths designated for use by cyclists from which motorised traffic is generally excluded...
, shared lane marking
Shared lane marking
A shared-lane marking or sharrow is a street marking installed at locations in Australia, Canada, and the United States. This marking is placed in the center of a travel lane to indicate that a bicyclist may use the full lane...
, traffic signs, road surface marking
Road surface marking
Road surface marking is any kind of device or material that is used on a road surface in order to convey official information. They can also be applied in other facilities used by vehicles to mark parking spaces or designate areas for other uses....
s and traffic lights.
Traffic engineering is closely associated with other disciplines:
- Transport engineeringTransport engineeringTransportation engineering is the application of technology and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation in order to provide for the safe, rapid, comfortable, convenient, economical, and environmentally...
- Pavement engineeringPavement engineeringPavement engineering is a branch of civil engineering that uses engineering techniques to design and maintain flexible and rigid pavements. This includes streets and highways and involves knowledge of soils, hydraulics, and material properties. Pavement engineering involves new construction as...
- Bicycle transportation engineeringBicycle transportation engineeringBicycle transportation engineering is the study of transportation engineering as it affects bicycles and cycling. It includes the design of dedicated transport facilities for cyclists, but also the study of how mixed-mode environments Bicycle transportation engineering is the study of...
- Highway engineeringHighway engineeringHighway engineering is an engineering discipline branching from civil engineering which involves the design, construction and maintenance of Highway Systems. Highway Engineering become prominent towards the latter half of the 20th Century after World War 2. Standards of highway engineering are...
- Transportation planningTransportation planningTransportation planning is a field involved with the evaluation, assessment, design and siting of transportation facilities .-Models and Sustainability :...
- Urban planningUrban planningUrban planning incorporates areas such as economics, design, ecology, sociology, geography, law, political science, and statistics to guide and ensure the orderly development of settlements and communities....
- Human factors engineeringHuman factorsHuman factors science or human factors technologies is a multidisciplinary field incorporating contributions from psychology, engineering, industrial design, statistics, operations research and anthropometry...
Typical traffic engineering projects involve designing traffic control device installations and modifications, including traffic signals, signs, and pavement markings. However, traffic engineers also consider traffic safety by investigating locations with high crash rates and developing countermeasures to reduce crashes. Traffic flow management can be short-term (preparing construction traffic control plans, including detour plans for pedestrian and vehicular traffic) or long-term (estimating the impacts of proposed commercial developments on traffic patterns). Increasingly, traffic problems are being addressed by developing systems for intelligent transportation systems, often in conjunction with other engineering disciplines, such as computer engineering
Computer engineering
Computer engineering, also called computer systems engineering, is a discipline that integrates several fields of electrical engineering and computer science required to develop computer systems. Computer engineers usually have training in electronic engineering, software design, and...
and electrical engineering
Electrical engineering
Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after commercialization of the electric telegraph and electrical...
.
Traffic systems
Traditionally, road improvements have consisted mainly of building additional infrastructure. However, dynamic elements are now being introduced into road traffic management. Dynamic elements have long been used in rail transport. These include sensors to measure traffic flows and automatic, interconnected, guidance systems to manage traffic (for example, traffic signs which open a lane in different directions depending on the time of day). Also, traffic flow and speed sensors are used to detect problems and alert operators, so that the cause of the congestion can be determined, and measures can be taken to minimize delays. These systems are collectively called intelligent transportation systems.Lane flow equation
The relationship between lane flow (Q, vehicles per hour), maximum speed (V, kilometers per hour) and density (K, vehicles per kilometer) isObservation on limited access facilities suggests that up to a maximum flow, speed does not decline while density increases. However, above a critical threshold, increased density reduces speed. Additionally, beyond a further threshold, increased density reduces flow as well.
Therefore, speeds and lane flows at bottlenecks can be kept high during peak periods by managing traffic density using devices that limit the rate at which vehicles can enter the highway. Ramp meter
Ramp meter
A ramp meter, ramp signal or metering light is a device, usually a basic traffic light or a two-section signal light together with a signal controller, that regulates the flow of traffic entering freeways according to current traffic conditions...
s, signals on entrance ramps that control the rate at which vehicles are allowed to enter the mainline facility, provide this function (at the expense of increased delay for those waiting at the ramps).
Highway safety
Highway safety engineering is a branch of traffic engineering that deals with reducing the frequency and severity of crashes. It uses physics and vehicle dynamics, as well as road user psychology and human factors engineering, to reduce the influence of factors that contribute to crashes.A typical traffic safety investigation follows these steps
- 1. Identify and prioritize investigation locations. Locations are selected by looking for sites with higher than average crash rates, and to address citizen complaints.
- 2. Gather data. This includes obtaining police reports of crashes, observing road user behavior, and collecting information on traffic signs, road surface markingRoad surface markingRoad surface marking is any kind of device or material that is used on a road surface in order to convey official information. They can also be applied in other facilities used by vehicles to mark parking spaces or designate areas for other uses....
s, traffic lights and road geometryGeometric design of roadsThe geometric design of roadways deals with the positioning of the physical elements of the roadway according to standards and constraints. The basic objective in geometric design is to provide a smooth-flowing, crash-free facility. Geometric roadway design can be broken into three main parts:...
.
- 3. Analyze data. Look for collisions patterns or road conditions that may be contributing to the problem.
- 4. Identify possible countermeasures to reduce the severity or frequency of crashes.
- • Evaluate cost/benefit ratios of the alternatives
- • Consider whether a proposed improvement will solve the problem, or cause "crash migration." For example, preventing left turns at one intersection may eliminate left turn crashes at that location, only to increase them a block away.
- • Are any disadvantages of proposed improvements likely to be than the problem you are trying to solve?
- 5. Implement improvements.
- 6. Evaluate results. Usually, this occurs some time after the implementation. Have the severity and frequency of crashes been reduced to an acceptable level? If not, return to step 2.
See also
- Bus laneBus laneA 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...
/ bus priorityBus priorityBus priority or transit signal priority is a name for various techniques to speed up bus public transport services at intersections with traffic signals amongst other methods. Trams and light rail vehicles can also be given priority...
/ bus rapid transitBus rapid transitBus rapid transit is a term applied to a variety of public transportation systems using buses to provide faster, more efficient service than an ordinary bus line. Often this is achieved by making improvements to existing infrastructure, vehicles and scheduling... - GridlockGridlockThe term gridlock is defined as "A state of severe road congestion arising when continuous queues of vehicles block an entire network of intersecting streets, bringing traffic in all directions to a complete standstill; a traffic jam of this kind." The term originates from a situation possible in...
- Hierarchy of roadsHierarchy of roadsThe hierarchy of roads categorizes roads according to their functions and capacities. While sources differ on the exact nomenclature, the basic hierarchy comprises freeways, arterials, collectors, and local roads....
- ITSIntelligent transportation systemThe term intelligent transportation systems refers to information and communication technology that improve transport outcomes such as transport safety, transport productivity, travel reliability, informed travel choices, social equity, environmental performance and network operation...
- MicrosimulationMicrosimulation-Introduction:Microsimulation is a category of computerized analytical tools that perform highly detailed analysis of activities such as highway traffic flowing through an intersection, financial transactions, or pathogens spreading disease through a population...
- Queueing theoryQueueing theoryQueueing theory is the mathematical study of waiting lines, or queues. The theory enables mathematical analysis of several related processes, including arriving at the queue, waiting in the queue , and being served at the front of the queue...
- Road safety auditRoad safety auditA Road Safety Audit is defined as "the formal safety performance examination of an existing or future road or intersection by an independent, multidisciplinary team...
- Road traffic control
- Road traffic safety
- Route assignmentRoute assignmentRoute assignment, route choice, or traffic assignment concerns the selection of routes between origins and destinations in transportation networks. It is the fourth step in the conventional transportation forecasting model, following trip generation, trip distribution, and mode choice...
- Signal timingSignal timingSignal timing is the technique which traffic engineers use to determine who has the right-of-way at an intersection. Signal timing involves deciding how much green time the traffic lights shall provide at an intersection approach, how long the pedestrian WALK signal should be, and many numerous...
- Traffic congestionTraffic congestionTraffic congestion is a condition on road networks that occurs as use increases, and is characterized by slower speeds, longer trip times, and increased vehicular queueing. The most common example is the physical use of roads by vehicles. When traffic demand is great enough that the interaction...
/ traffic flowTraffic flowTraffic flow, in mathematics and civil engineering, is the study of interactions between vehicles, drivers, and infrastructure , with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems.-History:Attempts to...
/ traffic signals - Three-phase traffic theory