Average Volumes

24-Hour GP versus HOV Vehicle Volume Profiles (by location)


How and Where 24-Hour GP vs HOV Vehicle Volume Profiles Were Measured

To investigate the effectiveness of the HOV system, vehicle volumes were analyzed at specific sites along major HOV corridors during morning and afternoon peak periods in the direction of the heaviest traffic flow. The results were then compared with the identical location, direction, and time periods for the GP lanes.

HOV lane vehicle volumes were estimated at eight sites [the list below is accurate for the graphs from the FLOW report but not for the graphs from the HOV report; make sure correct set of graphs matches with list] on the major freeway corridors (I-5, I-405, SR 520, I-90, SR 167) in the central Puget Sound area.  The sites were selected on the basis of their traffic significance as well as the availability of sufficient volume and vehicle occupancy data.  The locations used were as follows:



112th SW (Everett)
NE 137th Street (north Seattle)
Pearl Street (south of Seattle CBD)



NE 85th Street (Kirkland)
SE 52nd Street (south of I-90 interchange)


SR 520

84th Avenue NE (east of floating bridge)



Midspan (floating bridge)


SR 167

South 204th/208th (Kent)


How to Read 24-Hour GP vs HOV Vehicle Volume Profiles

The graphs in this section illustrate the number of vehicles traveling per lane per hour (vplph), as a function of time, on GP and HOV lanes measured at selected locations along Puget Sound freeway corridors.  Vehicle volumes were measured for the average 24-hour weekday for the year noted.  The GP volumes reported are for the average volume per lane for all lanes at that location. 

Like general purpose traffic volumes, HOV lane use varies by time of day and location.  In general, the more congestion an HOV lane can bypass, the greater incentive there is to use the HOV lane, and therefore the more people will use it.  Similarly, the better the transit service, the higher the number of people using transit in the HOV lane, which translates to higher person volumes in the HOV lane.  As a result, HOV vehicle volumes are generally at their peak during the traditional peak commute periods. HOV lane use on a given corridor generally increases near major urban employment centers.

Note that SR 520 HOV lane usage is affected by the more strict vehicle occupancy requirement on that facility (3+ persons per vehicle, vs. 2+ persons elsewhere).  Also, the I-90 HOV volumes shown are actually reversible lane volumes, which at this location on I-90 include mixed traffic (both HOVs and Mercer Island GP and HOV traffic).


Disclaimer. The contents of this Web page reflect the views of the authors/researchers, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Washington State Transportation Commission, Department of Transportation, or the Federal Highway Administration. The information presented does not constitute a standard, specification, or regulation.

Revised 19-Mar-2010