Seattle/Lake Washington Corridor Urban Partnership Agreement: National Evaluation Report
In 2006, the U.S. DOT initiated the UPA (Urban Partnership Agreement) program to demonstrate congestion reduction through strategies consisting of combinations of the 4Ts: Tolling, Transit, Telecommuting/TDM, and Technology. The Seattle/LWC UPA projects focused on reducing traffic congestion on SR 520 between I-405 and I-5, a heavily-traveled, east-west commuter route across Lake Washington. The lake separates Seattle from the eastern suburbs (including Bellevue and Redmond). These strategies included tolling all lanes of the SR 520 bridge, adding bus service in the SR 520 corridor, implementing active traffic management systems, and real-time traveler information signs on highways and at transit stops and stations. The suite of projects had a combined benefit-to-cost ratio of 1.76 due to travel time savings and reduced emissions.
Travel-time reliability, measured by the 95th percentile travel time, improved on SR 520 in the post-deployment period, declining in the morning peak period by approximately 3 minutes eastbound and 6 minutes westbound, and by 6 minutes eastbound and 13 minutes westbound in the afternoon peak period. The 95th percentile travel time on I-90 generally remained the same, but increased westbound in the afternoon peak period.