How far in advance of a bus stop should the driver begin activating hazard lights or use approved signal procedures to warn following traffic?

ADVANCE WARNING for bus stops protects both passengers (who must safely board and alight) and the bus from following traffic. On a surface street at 35 mph, a following vehicle traveling at the same speed needs 100+ feet of warning to safely slow and stop. On highways, warning distance should be proportionally longer. Many states and bus operators require specific signaling procedures for planned stops. The most dangerous bus crash type involving following vehicles is rear-end collisions at unannounced stops — advance warning eliminates this risk.