The 2010 Annual Congestion Report (pdf 1.7 mb), that examines 2009 traffic data to analyze the results of Moving Washington program, shows that in 2009 Washington’s highway users had faster commute experiences. This report found that the economic recession and the completion of major Moving Washington projects have contributed to reduced delay and shorter travel times across the state and on high demand Puget Sound corridors. However, continuing to reduce congestion long-term will remain a challenge.
Highlights from the 2010 Congestion Report
It provides in-depth analysis for 52 central Puget Sound and two Spokane commute routes and information on statewide transportation system performance. Selected highlights include (compare 2009 vs. 2007):
- The typical commuter spent nearly one hour less in congestion. Washingtonians experienced 22% less delay on state highways, while the estimated statewide economic costs for drivers (passenger cars and freight vehicles) and businesses due to delay dropped by 21%.
- Between 1% and 17% more vehicles used the system at eight, sampled, urban Puget Sound freeway locations.
- Average peak commute travel times shortened and improved on 31 of 38 routes in the Puget Sound, or better than four out of every five.
- The 95% reliability rating (the travel time that would virtually guarantee a commuter could reach his or her destination 19 out of 20 commute days) improved on 28 of the 38 routes.
- Eight of 14 HOV corridors met the reliability standard (45 mph or higher for 90% of the time) in 2009.
- VMT dropped statewide on all public roadways by 0.9% between 2007 and 2009, while it increased by 1.8% between 2008 and 2009.
- Before and After analysis of the results of completed projects show measurable benefits to commuters. This includes mobility improvements on I-405, I-5, SR 518, SR 18, SR 167, and I-205.
- The Incident Response program annual report examines results for 2007 and 2009.
- Comprehensive updates also include reports on the SR 167 High Occupancy Toll lanes between Auburn and Renton, and the latest information about the new Active Traffic Management (Smarter Highways) systems on I-5 near Seattle.
Data source and quality
WSDOT analysis primarily uses archived, measured real-time data, across the state, collected using the more than 5,000 induction loop detectors and other advanced ITS technologies such as Automated License Plate Reader (ALPR), floating car method, and tolling transponder data. In addition, this report also uses some HPMS data to calculate the statewide performance metrics where loop data does not exist. Other data sources used in this report include economic data, collision data, and transit ridership data, to name a few. WSDOT loop data undergoes a rigorous quality control process. Overall, WSDOT performs extensive data quality control on all data sets used in this analysis.
Congestion Performance metrics
In order to provide a compressive analysis of system performance, WSDOT uses more than 20 different metrics to define and describe congestion trends in Washington State. These metrics include delay, travel time, duration of congestion, travel time reliability, and maximum throughput travel time index. For a list of key metrics please see page 9 of the 2010 Congestion Report.
Maximum throughput as the basis for performance analysis
WSDOT aims at maximizing the system efficiency by striving to achieve the speed at which the highest number of vehicles can move through a highway segment. Research shows that the maximum system throughput is achieved at 70%-85% of posted speed limit. Maximum throughput speed is a dynamic speed threshold that changes over the period of time due to many other factors such as highway geometrics, driver behavior, weather to name a few. Thresholds for calculating the various metrics can be viewed on page 11 of the Congestion Report.