This study examined how the I-405\nexpress lanes\u2014the Washington State Department of Transportation\u2019s (WSDOT)\nnewest dynamically tolled facility\u2014are\nused, the benefits they provide to users, and how these benefits are\ndistributed among different groups of noncommercial users. The project provided\nunique insight into facility usage patterns and equity impacts associated with\ndifferent income and geographic groups. <\/p>\n\n\n\n
The complex operating environment of I-405 between Bellevue and Lynnwood, Washington, includes parallel general purpose and high occupancy toll lanes, variable length and variable cost roadway segments, variable high occupancy vehicle definitions (2+ or 3+ depending on time of day), a variety of geometric merge\/diverge designs, and both one- and two-lane tolled segments. WSDOT is interested in gaining a better understanding of how user behavior affects corridor performance, given the dynamic prices and geometric variation in the corridor. <\/p>\n\n\n\n
Huge\namounts of data were available to study these interactions. The project team had access to data on the\nprice, time, and location of individual users\u2019 payments from over 16 million trips on the I-405 express toll\nlanes during all operational hours of 2018 (weekdays 5:00 AM \u2013 7:00 PM). They also\nused demographic data by census block groups; and speed, volume, and travel\ntime data for both the express toll and general purpose lanes. <\/p>\n\n\n\n
By\nconnecting hashed individual IDs (toll accounts or license plates) to census\nblock group information, the researchers were able to develop an understanding\nof who used the facility where and when, and thus how facility benefits were distributed\u2014all\nwithout invading the privacy of drivers. <\/p>\n\n\n\n
A\nwide range of information was derived by combining these data sets, including\nrevealed value of time and value of reliability (both overall and by time of\nday and direction), price elasticities, usage by income group, total net benefits\ngained by income group, and per trip benefits by income group, as well as basic\nusage statistics such as entry\/exit patterns by time of day.<\/p>\n\n\n\n
Not surprisingly, higher income groups were found to use the\nfacility more often and therefore to obtain a larger share of the benefits per\nuser than lower income groups. However, lower income users were found to\nactually obtain higher net benefits per trip than higher income groups. This is\nbecause they used the facility more strategically. In addition, while lower\nincome drivers paid to use the facility less often than higher income users, a\nlarge number of them used the facility at least periodically during the year.<\/p>\n\n\n\n