Passenger car equivalent
Encyclopedia
Passenger Car Equivalent (PCE), 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:
Highway capacity is measured in PCE/hour daily
Passenger Car Equivalent is also sometimes used interchangeably with Passenger car unit (PCU).
A common method used in the USA
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 following is not the norm. This complicates computing of PCE.
Using multiple heuristic
techniques, transportation engineers convert a mixed traffic stream into a hypothetical passenger-car stream.
examples:
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:
Transport engineering
Transportation engineering is the application of technology and scientific principles to the planning, functional design, operation and management of facilities for any mode of transportation in order to provide for the safe, rapid, comfortable, convenient, economical, and environmentally...
, to assess traffic-flow rate
Traffic flow
Traffic flow, in mathematics and civil engineering, is the study of interactions between vehicles, drivers, and infrastructure , with the aim of understanding and developing an optimal road network with efficient movement of traffic and minimal traffic congestion problems.-History:Attempts to...
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 0.5
- bicycle 0.2
- horse drawn vehicle 4
- bus, tractor, truck 3.5
Highway capacity is measured in PCE/hour daily
Passenger Car Equivalent is also sometimes used interchangeably with Passenger car unit (PCU).
A common method used in the USA
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
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
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, 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
Heuristic
Heuristic refers to experience-based techniques for problem solving, learning, and discovery. Heuristic methods are used to speed up the process of finding a satisfactory solution, where an exhaustive search is impractical...
techniques, transportation engineers convert a mixed traffic stream into a hypothetical passenger-car stream.
UK values
In the UK, the Department for Transport recommend these values:- Motorbike 0.4
- Car 1.0
- LGV 1.0
- RGV 1.9
- Articulated goods vehicle 2.9
- PSV (bus) 2.5
Methods
Many methods exist for determining passenger car units (PCUs)examples:
- homogenization coefficient,
- semi-empirical method,
- Walker’s method,
- headway method,
- multiple linear regressionLinear regressionIn statistics, linear regression is an approach to modeling the relationship between a scalar variable y and one or more explanatory variables denoted X. The case of one explanatory variable is called simple regression...
method - simulation method.
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.