An intersection approach has a saturation flow rate of 1500 veh/h, and vehicles arrive at the approach at the rate of 800 veh/h.

The approach is controlled by a pretimed signal with a cycle length of 60 seconds and D/D/1 queuing holds.

Local standards dictate that signals should be set such that all approach queues dissipate 10 seconds before the end of the effective green portion of the cycle.

Assuming that approach capacity exceeds arrivals, determine the maximum length of effective red that will satisfy the local standards.