Effects of Full-Facility Variable Tolling on Traveler Behavior: Evidence from a Panel Study of the Sr-520 Corridor in Seattle, Washington

Variable tolling was implemented on the SR-520 Bridge in the Seattle, Washington, region in 2011 as part of a federally funded initiative to reduce traffic congestion. R-520 tolls varied by time of day up to a maximum of $3.50 each way ($5 for nontransponder payments). A nearby parallel facility, Interstate 90, remained a toll-free alternative across Lake Washington. Tolling was accompanied by investments in public transit and traffic management technologies and by efforts to promote telecommuting. A two-stage panel survey approach was used to analyze the impacts of this tolling program on corridor users’ daily travel choices. In each survey wave, more than 3,000 respondents from roughly 2,000 households completed a 2-day travel diary, with additional detail on trips in the Lake Washington corridor, plus a personal survey on general travel behavior and attitudes. Key survey findings included a marked decrease in respondents’ travel in the corridor after tolling, particularly on SR-520, which experienced a 47% reduction in recorded trips, and significant diversion to I-90. Shifts from SR-520 to I-90 were most pronounced among men, those in lower-income households, and those with less workplace schedule flexibility. There were also increases in transit mode share in the corridor, while carpooling and telecommuting levels were relatively stable. In the posttolling survey, respondents registered an overall increase in satisfaction with their commutes and less stress associated with driving. Reported satisfaction with the speed and reliability of individual trips on SR-520 also increased substantially, and personal attitudes shifted slightly in favor of tolling.