ACTS

Roadway Friendliness Tool

Treatment 9: All-red Clearance Interval

Institute of Traffic Engineers (ITE) Guidelines: This treatment is optional.

Where might you find this on your system: You may find this at all traffic signals.

Recommendation: Motorists tend to drive impatiently at traffic signals, often using the entire yellow phase as if it were green. This results in motorists occupying the center of an intersection, or just beginning to enter the intersection, when their light turns red. It is recommended that the red indication for cross-traffic be extended for approx 1-to-2.5 seconds prior to display of green to the cross traffic. ITE provides guidelines for calculating length of yellow and all-red intervals.

Conflicts with other community goals: All-red intervals, by stopping traffic on all approaches, reduce capacity by a slight amount, thereby increasing motorist delay by a slight amount.

Ease of implementation: Re-timing of traffic signal cycles to provide or increase all-red interval requires engineering expertise in the planning stage, and electrical expertise in the installation. If it is done as an isolated correction, the planning is limited to one hour, and the fieldwork is performed on the controller box at the side of the road by one-person crew with no special equipment.

However, a correction to provide all-red at an intersection might be coupled with a complete re-timing of all lane movements. This more thorough approach to signal timing would require planning studies to document current volumes at each approach. This is needed anyway and should not be charged against the all-red improvement.

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Roadway Friendliness Tool