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Transit Street Design Guide Index

Transit Street Design Guide
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Signals & Operations

Signals & Operations

Traffic signals must not be considered in isolation, but rather as a system of multiple intersections. Because delay at traffic signals often accounts for one-quarter to one-third of a transit route’s total trip time, it is important to consider settings and technology that optimize the performance of the system—ideally, to keep transit vehicles moving between stops. In many cities, traffic signals and progression were traditionally designed primarily for auto traffic with little regard for other street users, especially transit.

Signal strategies should focus on the goal of moving people rather than favoring a single mode. Specific actions can increase transit convenience, reliability, and predictability while improving general traffic operations for all users. With or without transit signal priority, signal timing plans should be optimized to reduce person delay rather than vehicle delay, favoring pedestrian mobility. The signal network helps achieve goals of both the local agency’s policies as well as broader regional transit plans.

Subsections:

Transit Signal Progression

Transit Signal Progression

Transit signal progressions, a form of pre-timed or “passive” transit signal priority, are signal progressions (green waves) set to realistic travel speeds for on-street transit, often in the 12–20 mph range.

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Active Transit Signal Priority

Active Transit Signal Priority

Transit Signal Priority (TSP) tools modify traffic signal timing or phasing when transit vehicles are present either conditionally for late runs or unconditionally for all arriving transit.

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Short Signal Cycles

Short Signal Cycles

When transit has unpredictable dwell times, or where there is no coordinated signal progression, shortening signal cycle length can greatly reduce the time spent by transit vehicles waiting at red signals.

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Turn Restrictions

Turn Restrictions

Prohibiting turns where they present issues, and shifting turn volume to the intersections where they can be best accommodated—with signal phases and turn lanes—can improve transit performance, general traffic performance, and walking and bicycling safety at the same time.

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References