Traffic engineering is a branch of

civil engineering Civil engineering is a regulation and licensure in engineering, professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads ...

that uses

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

techniques to achieve the safe and efficient movement of people and goods on roadways. It focuses mainly on research for safe and efficient

traffic flow In transportation engineering, traffic flow is the study of interactions between travellers (including pedestrians, cyclists, drivers, and their vehicles) and infrastructure (including highways, signage, and traffic control devices), with the ai ...

, such as

road A road is a thoroughfare used primarily for movement of traffic. Roads differ from streets, whose primary use is local access. They also differ from stroads, which combine the features of streets and roads. Most modern roads are paved. Th ...

geometry, sidewalks and crosswalks,

cycling infrastructure Cycling, also known as bicycling or biking, is the activity of riding a bicycle or other types of bicycle pedal, pedal-driven human-powered vehicles such as balance bikes, unicycles, tricycles, and quadricycles. Cycling is practised around the ...

traffic signs Traffic signs or road signs are signs erected at the side of or above roads to give instructions or provide information to road users. The earliest signs were simple wooden or stone milestones. Later, signs with directional arms were introduce ...

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 are commonly placed with road marking machines (also referred to as road marking equipment or pavement marking eq ...

s and

traffic lights Traffic lights, traffic signals, or stoplights – also known as robots in South Africa, Zambia, and Namibia – are signaling devices positioned at road intersections, pedestrian crossings, and other locations in order to control the flow o ...

. Traffic engineering deals with the functional part of transportation system, except the infrastructures provided. Traffic engineering is closely associated with other disciplines: *

Transport engineering Transportation engineering or transport engineering is the application of technology and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation to provide for the safe, ...

Pavement engineering Pavement engineering is a branch of civil engineering that uses engineering techniques to design and maintain flexible (asphalt) and rigid (concrete) pavements. This includes streets and highways and involves knowledge of soils, hydraulics, and mat ...

Bicycle transportation engineering Bicycle transportation planning and engineering are the disciplines related to transportation engineering and transportation planning concerning bicycles as a mode of transport and the concomitant study, design and implementation of cycling infra ...

Highway engineering Highway engineering (also known as roadway engineering and street engineering) is a professional engineering discipline branching from the civil engineering subdiscipline of transportation engineering that involves the planning, design, construct ...

Transportation planning Transportation planning is the process of defining future policies, goals, investments, and spatial planning designs to prepare for future needs to move people and goods to destinations. As practiced today, it is a collaborative process that i ...

Urban planning Urban planning (also called city planning in some contexts) is the process of developing and designing land use and the built environment, including air, water, and the infrastructure passing into and out of urban areas, such as transportatio ...

Human factors engineering Ergonomics, also known as human factors or human factors engineering (HFE), is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Primary goals of human factors engi ...

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 and residential developments on traffic patterns). Increasingly, traffic problems are being addressed by developing systems for

intelligent transportation system An intelligent transportation system (ITS) is an advanced application that aims to provide services relating to different modes of transport and traffic management and enable users to be better informed and make safer, more coordinated, and 's ...

s, often in conjunction with other engineering disciplines, such as

computer engineering Computer engineering (CE, CoE, or CpE) is a branch of engineering specialized in developing computer hardware and software. It integrates several fields of electrical engineering, electronics engineering and computer science. Computer engi ...

and

electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

. Traffic engineers also set a

design speed The design speed is a tool used to determine geometric features of a new road or street during road design. Contrary to the word's implication, the design speed of the road or street is not necessarily its vehicle speed limit or maximum safe spe ...

for roads, and sometimes collect data that sets the legal speed limit, such as when the

85th percentile speed Speed limits on road traffic, as used in most countries, set the legal maximum speed at which vehicles may travel on a given stretch of road. Speed limits are generally indicated on a traffic sign reflecting the maximum permitted speed, express ...

method is used.

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 An intelligent transportation system (ITS) is an advanced application that aims to provide services relating to different modes of transport and traffic management and enable users to be better informed and make safer, more coordinated, and 's ...

Lane flow equation

The relationship between lane flow (''Q'', vehicles per hour), space mean speed (''V'', kilometers per hour) and density (''K'', vehicles per kilometer) is Observation on limited access facilities suggests that up to a maximum flow, speed does not decline while density increases. However, above a critical threshold (BP, breakpoint), 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 A ramp meter, ramp signal, or metering light is a device, usually a basic traffic light or a two-section signal light (red and green only, no yellow) together with a signal controller, that regulates the flow of traffic entering freeways accordi ...

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

and road geometry. :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 worse 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.

Traffic Engineering Societies

Institute of Transportation Engineers The Institute of Transportation Engineers (ITE) is an international educational and scientific association of transportation professionals who are responsible for meeting mobility and safety needs. ITE facilitates the application of technology and ...

(ITE), an international membership society of transportation engineers, founded in 1930. * Transportation & Development Institute (T&DI) of the

American Society of Civil Engineers The American Society of Civil Engineers (ASCE) is a tax-exempt professional body founded in 1852 to represent members of the civil engineering profession worldwide. Headquartered in Reston, Virginia, it is the oldest national engineering soci ...

(ASCE)

References

* Das, Shantanu and Levinson, D. (2004). "A Queuing and Statistical Analysis of Freeway Bottleneck Formation". ''ASCE Journal of Transportation Engineering'' Vol. 130, No. 6, November/December 2004, pp. 787–795 * Homburger, Kell and Perkins, ''Fundamentals of Traffic Engineering, 13th Edition'', Institute of Transportation Studies, University of California (Berkeley), 1992.

External links