Free Traffic Flow Calculator
Calculate traffic flow rate from vehicle density and average speed using the fundamental traffic flow relationship.
veh/km
km/h
Traffic Flow Rate (q)
1,800 veh/h
Average Time Headway2.0 seconds
Average Spacing33.3 m
Traffic Flow Rate (q) vs Vehicle Density (k)
Fundamental Traffic Flow Equation
Traffic flow, density, and speed are linked by a fundamental relationship.
Formula
q = k u
where q is flow rate (vehicles/hour), k is density (vehicles/km), and u is space mean speed (km/h).
Time headway = 3600/q seconds. Spacing = 1000/k metres. At capacity, flow is maximised with moderate speed and density.
Example Calculation
30 vehicles per km travelling at 60 km/h.
- 01q = 30 x 60 = 1800 vehicles/hour
- 02Headway = 3600 / 1800 = 2.0 seconds
- 03Spacing = 1000 / 30 = 33.3 m between vehicles
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