Flow, AADT And Journey Speed

Flow (Volume) (Q)

The number of vehicles passing a specified point during a stated period of time is called flow. It is usually expressed in vehicles per hour.

For examples,

At a particular section of road, if 600 vehicles passes in a time period of 1 hour, then the flow or traffic volume is 600 vehicles/hour. Maximum possible flow is traffic capacity.

AADT (Average Annual Daily Traffic)

It is the average of 24 hours volume count collected every day in the year.

∴ AADT = Total annual flow/365

It is useful for,

  • Computing accident rates
  • Estimating highway user revenue
  • Planning major streets
  • Improvement, construction or reconstruction of roads

Journey speed (Travel speed or Overall speed)

It is the effective speed with which a vehicle traverse a particular route between two stations.

Journey speed = Total distance travelled/Total time taken(including delays)

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