Passenger car equivalent

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Passenger Car Equivalent (PCE), is a metric used in Transportation Engineering, to assess traffic-flow rate on a highway.

Highway capacity is measured in PCE/hour.

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.

Many methods exist for determining passenger car units (PCUs)
examples:

• homogenization coefficient,
• semi-empirical method,
• Walker’s method,
• headway method,
• multiple linear regression method
• simulation method.