The signal timing for this strategy is
noticeably different than the corresponding timing for equalizing the v/c
The previously equal v/c ratios for the
competing movements now vary from 0.49 to 1.0 as a result of
redistributing the green times.
The critical v/c ratio for the whole
intersection has not changed from its previous value of 0.83. The critical
v/c ratio is not affected by the distribution of green times. The
computations for this performance measure are always based on the
assumption of equal v/c ratios. This is an important point. The critical
v/c ratio is a measure of overall intersection sufficiency and does not
reflect the actual distribution of green times.
The control delays are now in much
closer agreement among the competing movements. The EB through movement
still has a slightly lower delay (47 sec per vehicle vs. 52 sec per
vehicle for the other two movements). Note that the v/c for this movement
is 1.0. To fully equalize the delays for all movements, the EB through
movement would have to be forced to operate beyond its capacity. It is
common signal timing practice to halt the iterative distribution of green
times when further redistribution would create an oversaturated movement.
In spite of the slight difference
control delay values, LOS D now applies to all of the competing movements
and to the overall intersection.