Traffic engineering (transportation)

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Traffic engineering is a branch of civil engineering that uses engineering techniques to achieve the safe and efficient movement of people and goods. It focuses mainly on research and construction of the immobile infrastructure necessary for this movement, such as roads, railway tracks, bridges, traffic signs and traffic lights.

Increasingly however, instead of building additional infrastructure, dynamic elements are also introduced into road traffic management (they have long been used in rail transport). These use sensors to measure traffic flows and automatic, interconnected guidance systems (for example traffic signs which open a lane in different directions depending on the time of day) to manage traffic especially in peak hours.

The relationship between lane flow (Q) (vehicles per hour) maximum speed (V) (kilometers per hour) and density (K) (vehicles per kilometer) is Q = KV. Observation on limited access facilities suggests that up to a maximum flow, speed does not decline while density increases, but above a critical threshold, increased density reduces speed, and beyond a further threshold, increased density reduces flow as well.

Therefore, managing traffic density by limiting the rate that vehicles enter the highway during peak periods can keep both speeds and lane flows at bottlenecks high. Ramp meters, 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).

Traffic engineering is closely associated with other disciplines:

• Transportation engineering
• Traffic congestion
• Highway engineering
• Transportation planning
• Urban planning
• Route assignment

[edit] See also

• Hierarchy of roads
• Queuing theory
• Traffic flow
• Gridlock
• Traffic signals and Signal timing
• Intelligent Transportation System

[edit] References

• Homburger, Kell and Perkins, Fundamentals of Traffic Engineering, 13th Edition, Institute of Transportation Studies, University of California (Berkeley[1]), 1992.
• 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