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Saturation (traffic)
In traffic engineering, saturation describes the maximum traffic flow which can be handled by a junction. The saturation flow is the rate at which a continuous flow of vehicles can pass through a constant green signal, typically expressed in vehicles per hour or PCUs per hour. A formula to calculate saturation flows based on lane geometry is given in Transport and Road Research Laboratory RR67. However, the formula can over-estimate saturation flows at congested locations. Degree of Saturation The degree of saturation (DoS) of an intersection (typically under traffic signal control) or a link measures the demand relative to the total capacity. A DoS value of 100% meaning that demand and capacity are equal and no further traffic is able to progress through the junction. The formula to calculate DoS is: *Degree of saturation = (demand x cycle time) / (saturation flow x effective green time) Values over 85%-90% typically indicate traffic congestion Traffic congestion is a con ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Engineering (transportation)
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 for safe and efficient traffic flow, such as road geometry, sidewalks and crosswalks, cycling infrastructure, traffic signs, road surface markings and traffic lights. Traffic engineering deals with the functional part of transportation system, except the infrastructures provided. Traffic engineering is closely associated with other disciplines: *Transport engineering *Pavement engineering *Bicycle transportation engineering *Highway engineering *Transportation planning *Urban planning *Human factors engineering Typical traffic engineering projects involve designing traffic control device installations and modifications, including traffic signals, signs, and pavement markings. Examples of Engineering Plans include pole engineering analysis and Storm Water Prevention Programs (SWPP). However ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Passenger Car Unit
Passenger car equivalent (PCE) or passenger car unit (PCU) is a metric used in transportation engineering, to assess traffic-flow rate on a highway. A passenger car equivalent is essentially the impact that a mode of transport has on traffic variables (such as headway, speed, density) compared to a single car. For example, typical values of PCE (or PCU) are: *private car (including taxis or pick-up) 1 *motorcycle 0.75 *bicycle 0.5 *horse-drawn vehicle 4 *bus, tractor, truck 3 Highway capacity is measured in PCE/hour daily A common method used in the US is the density method. However, the PCU values derived from the density method are based on underlying homogeneous traffic concepts such as strict lane discipline, car following and a vehicle fleet that does not vary greatly in width. On the other hand, highways in India, carry heterogeneous traffic, where road space is shared among many traffic modes with different physical dimensions. Loose lane discipline prevails; car followi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Signal
Traffic lights, traffic signals, or stoplights – known also as robots in South Africa are signalling devices positioned at road intersections, pedestrian crossings, and other locations in order to control flows of traffic. Traffic lights consist normally of three signals, transmitting meaningful information to drivers and riders through colours and symbols including arrows and bicycles. The regular traffic light colours are red, yellow, and green arranged vertically or horizontally in that order. Although this is internationally standardised,1968, as revised 1995 and 2006Vienna Convention on Road Signs and Signals United Nations Publication ECE/TRANS/196. ISBN 978-92-1-116973-7. URL Accessed: 7 January 2022. variations exist on national and local scales as to traffic light sequences and laws. The method was first introduced in December 1868 on Parliament Square in London to reduce the need for police officers to control traffic. Since then, electricity and computerised c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traffic Congestion
Traffic congestion is a condition in transport that is characterized by slower speeds, longer trip times, and increased vehicular queueing. Traffic congestion on urban road networks has increased substantially since the 1950s. When traffic demand is great enough that the interaction between vehicles slows the speed of the traffic stream, this results in some congestion. While congestion is a possibility for any mode of transportation, this article will focus on automobile congestion on public roads. As demand approaches the capacity of a road (or of the intersections along the road), extreme traffic congestion sets in. When vehicles are fully stopped for periods of time, this is known as a traffic jam or (informally) a traffic snarl-up. Traffic congestion can lead to drivers becoming frustrated and engaging in road rage. Mathematically, traffic is modeled as a flow through a fixed point on the route, analogously to fluid dynamics. Causes Traffic congestion occurs when ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
