Highway Capacity Calculator

Estimate the maximum flow rate for a segment of highway under prevailing conditions.

Ideal Capacity per Lane (pc/hr/ln)

Typical: 2400 pc/hr/ln for freeways.

Number of Lanes (one direction)

e.g., 2, 3, 4 lanes.

Lane Width (ft)

Affects Lane Width Factor ($f_{LW}$).

Percentage of Heavy Vehicles (%)

e.g., 5% for cars, 10% for trucks/buses.

Passenger Car Equivalent for Trucks ($E_T$)

Varies by terrain/grade (e.g., 1.5-4.0).

Driver Population Factor ($f_p$)

Accounts for unfamiliar drivers.

Results

Estimated Highway Capacity:

passenger cars per hour (pc/hr)

Ideal Capacity: Max flow under perfect conditions.
Lane Width Factor ($f_{LW}$): Reduces capacity for narrow lanes.
Heavy Vehicle Factor ($f_{HV}$): Accounts for slower, larger vehicles. Calculated as: $1 / (1 + P_T(E_T – 1))$, where $P_T$ is the proportion of trucks and $E_T$ is the Passenger Car Equivalent for trucks.
Driver Population Factor ($f_p$): Reflects driver familiarity (e.g., commuters vs. recreational).

This calculator uses a simplified model based on Highway Capacity Manual (HCM) principles. For precise engineering, consult the latest HCM edition.