Congestion Monitoring
Speed as Percent of Speed Limit
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Congestion Monitoring |
The City of Vancouver and Clark County collect PM peak period travel time for concurrency purposes along concurrency corridors. RTC has contracted to collect AM peak and additional PM peak travel time data in corridors not covered by the concurrency data collection effort. Travel speed is computed from the travel time data. It consists of utilizing the travel time and distance to calculate an average travel speed. Speed was then converted to a percent of posted speed for each of the congestion management corridors.
The speed percentage for the freeway facilities are generally close to the posted speed limit. While facilities with multiple signalized intersections are generally between 65% and 80% of the posted speed limit. While speed alone is not an indicator of congestion, higher speed facilities are more attractive and generally carry more vehicles.
In the PM peak, arterials and freeways generally display lower percentages of speed compared to speed limit, due to higher congestion. In the PM period, Highway 99, Hazel Dell, Main Street, 112th Avenue, St. Johns/Ft. Vancouver, Andresen Road, 137th Avenue, Fourth Plain, Mill Plain, 78th/76th Street, Burton Road, 18th Street and Mill Plain East operate at less than 65% of the posted speed.
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