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.
Traffic studies and/or analysis must be done to obtain the number of trips, which shall then be converted to PCUs based on the above standards. Each region has its own manual with regards to PCU equivalence factors. 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
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
carry heterogeneous traffic, where road space is shared among many traffic modes with different physical dimensions. Loose lane discipline prevails; car following is not the norm. This complicates computing of PCE.
Using multiple
heuristic
A heuristic or heuristic technique (''problem solving'', '' mental shortcut'', ''rule of thumb'') is any approach to problem solving that employs a pragmatic method that is not fully optimized, perfected, or rationalized, but is nevertheless ...
techniques, transportation engineers convert a mixed traffic stream into a hypothetical passenger-car stream.
Methods
Many methods exist for determining passenger car units (PCUs).
Examples:
* homogenization coefficient,
* semi-empirical method,
* Walker's method,
* headway method,
* multiple
linear regression
In statistics, linear regression is a statistical model, model that estimates the relationship between a Scalar (mathematics), scalar response (dependent variable) and one or more explanatory variables (regressor or independent variable). A mode ...
method
* simulation method.
Transport for London recommend the following PCU values in an urban context:
* Pedal cycle 0.2
* Motorcycle 0.4
* Car or light goods vehicle 1.0
* Medium goods vehicle 1.5
* Bus or coach 2.0
* Heavy goods vehicle (HGV) 2.3
It may be appropriate to use different values for the same vehicle type according to circumstances. For example, in the UK in the 1960s and 1970s, bicycles were evaluated thus:
*on rural roads 0.5
*on urban roads 0.33
*on roundabouts 0.5
*at traffic lights 0.2.
References
Transportation engineering
Equivalent units
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