Determination of theoretical capacity of highway
The equation for the estimation of theoretical capacity or basic capacity of a single lane is,
C = 1000V/S
Where,
C = Capacity in vehicles/hr per lane
V = Vehicle speed in kmph
S = Average spacing in meters of moving vehicles
The value of S is obtained from actual field observations; alternatively, it can be calculated from safe stopping sight distance considerations involving total reaction time and baking distance, and the total length of the vehicles, L, in meters. This spacing is also equal to space headway.
The minimum space headway S = [Minimum space gap (perception time braking distance)] + [Average length of vehicle (L)]
S = 0.278∙V∙t + V2/254f + L
Where,
L = Length of vehicle (m)
t = Perception reaction time (sec)
V = Speed (kmph)
f = Friction factor
