Traffic engineering is a branch ofcivil engineering that usesengineering techniques to achieve the safe and efficient movement of people and goods on roadways. It focuses mainly on research for safe and efficienttraffic flow, such asroad geometry,sidewalks andcrosswalks,cycling infrastructure,traffic signs,road surface markings andtraffic lights. Traffic engineering deals with the functional part of transportation system, except the infrastructures provided.
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 and residential developments on traffic patterns). Increasingly, traffic problems are being addressed by developing systems forintelligent transportation systems, often in conjunction with other engineering disciplines, such ascomputer engineering andelectrical engineering. Traffic engineers also set adesign speed for roads, and sometimes collect data that sets the legal speed limit, such as when the85th percentile speed method is used.
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 calledintelligent transportation systems.
The relationship between lane flow (Q, vehicles per hour), space mean speed (V, kilometers per hour) and density (K, vehicles per kilometer) is
Observation onlimited 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 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).
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]
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