Congestion Management Process
Report Summary
2001

Congestion Management Network

The CMP corridors consist of regional facilities that are currently or are likely to become congested. They form a subset of the Vancouver/Clark County Regional Transportation System. The congestion management network is made up of thirty corridors. The endpoints for each corridor represent locations where the characteristics of the corridor change significantly.

A corridor approach that incorporates parallel routes and transit services provides a regional orientation and responds to the multimodal and alternative travel themes of the Federal Transportation Act. Although grouped by corridors, data is reported for individual facilities.

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Corridor Capacity Ratio

The corridor capacity ratio is an aggregation of the volume/capacity (V/C) ratios for the individual segments that make up a facility within a corridor. For each segment in a corridor, the V/C ratio, vehicle miles traveled (VMT), and VMT-weighted V/C ratio (the product of the V/C ratio and VMT) for the peak hour are calculated. The CCR is the sum of the weighted link ratios. It is intended to show the overall V/C ratio for the length of a corridor instead of a single location on the facility.

The PM periods show congestion along major facilities such as I-5, I-205, SR-14, SR-500/Fourth Plain, Burton/18th Street, 164th Avenue, Ward Road, Mill Plain-East, SR-503-South, and SR-502. Planned improvements along Ward Road and Burton Road are likely to reduce the congestion index in these corridors.

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Corridor Speed as Percent of Speed Limit

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.

In general, facilities with at-grade intersections, display lower speed percentages. The speed percentages for freeway facilities are close to 100% of the posted speed limit. The eastern portion of Mill Plain, Southern portion of 164th Avenue, and eastern portion of SR-500 displays the lowest percentages of speed in the PM period.

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Auto Vehicle Occupancy

Automobile occupancy is calculated by counting passenger vehicles at a given location and the number of people in each vehicle. The number of people divided by the number of passenger vehicles is the automobile occupancy for that location. Automobile occupancy information has been collected at twenty locations throughout Clark County.

In general, freeway facilities display lower auto vehicle occupancy than arterial facilities. This difference is likely due to a greater number of work trips on freeways, where drive alone trips are more prominent. The 2001 automobile occupancy data showed a decrease in vehicle occupancy on freeways in both AM and PM time periods, with the exception of I-5 South in the AM peak where an HOV Lane was implemented.

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Truck Percentage

Traffic counts collected for the CMS include several locations that also classify vehicles according to the number of axles. Trucks are defined as vehicles with more than two axles, such as typical tractor/trailer rigs, travelling on the roadway during the peak period. This is a measure of trucks as a percentage of all vehicles travelling on the roadway.

Overall, the freeway facilities and SR-501 accessing the Port of Vancouver display the highest percentage of truck volumes during the PM peak period. The exception to this is on SR-500, which has truck percentages similar to major arterials, such as Andresen Road and 164th Avenue. SR-14, I-5 and I-205 corridors have truck percentages of 5% or higher. Fourth Plain Boulevard/SR-501 from I-5 to the Port of Vancouver has the highest percentage at 17.9% of PM peak vehicle volumes. (Count was taken prior to the completion of the Mill Plain Extension). I-5 North and I-205 Central also have significant truck percentages (13.8% and 10.3%).

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This report was prepared by: