1. CHAPTER 2: Highway Capacity
Example 3:
New urban facility being planned with a forecast opening-day AADT of 75,000 veh/day.
What is the minimum number of lanes needed to provide at least LOS D during the peak hour on opening day?
What are the speed and density of traffic for the
proposed number of lanes?
Given information:
75,000 veh/day (both directional), K=0.090, Directional Split (55/45), FFS = 110km/h (field), PHF = 0.9, Rolling terrain, 10 percent trucks.

2. Solution: CHAPTER 2: Highway Capacity
- Convert AADT to design-hour volume.
DDHV = AADT * K * D
DDHV = 75,000 * * 0.55
DDHV = 3,713 veh/h.
- Find, fHV = =
1 + PT(ET – 1)+ PR(ER – 1) (2.5 – 1) + 0
fHV = 0.870
(Try 4 lanes)
Adjusted volume, vp = ,713
(0.90)(2)(0.870)(1.00)
= 2,371 pc/h/ln (LOS F)!
(Try 6 lanes), vp = ,713
(0.90)(3)(0.870)(1.00)
= 1,581pc/h/ln (LOS C) OK!
Density,
vp / s = 14.4 pc/km/ln.