Uniform Intersection Delay (Webster d1)

d_{1} = \frac{0.5 C ( 1 - g / C ) ^{2}}{1 - [ min ( X , 1 )] ( g / C )}

First term of HCM/Webster delay: uniform delay from the red. Overflow delay d2 is added when X is high. LOS is from control delay per vehicle.

Step-by-step solved example

C=60 s, g/C=0.5, X=0.6. d1?

Red wait: uniform delay d1 from the cycle and g/C.

Answer: d1 ≈ 11 s/veh

0/10 correct

1.If X=0 and g/C=0.5, d1=

2.LOS E for signalized intersections is about

3.d2 overflow grows quickly as

4.C=90, g/C=1 (all green): d1=

5.Arrival type / progression factor PF

6.Unsignalized HCM delay uses

7.C=120, 1−g/C=0.6, X=0: d1=

8.Control delay includes

9.A two-phase vs eight-phase plan

10.v/c in the d1 denominator uses min(X,1) so that