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Planning Guidance for the Installation and Use of Technology Devices for Transportation Operations and Maintenance

ENTERPRISE Transportation Pooled Fund Study

VSL Guideline 2 - Safe Stopping Distances

Purpose: To encourage travel at speeds that are conducive to stopping safely for stopped or slowed vehicles (e.g. crashes, stalls, other incidents).

Engineering judgment should be used to assess potential implications that may result from installation of VSL. This planning guidance does not mandate the use of VSL.

1. The freeway peak hour volume exceeds 1100 vphpl.

AND

2. The rear-end, lane-change, or side-swipe crash rate for the segment is higher than expected for the local area.

AND

3. It has been observed that there is a significantly higher rate of secondary crashes on the candidate segment than other similar roadway segments.

AND

4. There is a regularly occurring significant speed differential of at least 10 mph of travel speeds below posted speeds between the upstream and downstream locations of the segment (e.g. a downstream bottleneck location has typical speeds that are slower than an upstream location). (1)

Reference:

1. MUTCD. 2009.