The Pros and Cons of Using the Change in Destination Choice Logsums as a Practical Measure of User Benefits
Corresponding Author: David Ory, Sidewalk Labs
Presented By: Kristen Villanueva, Metropolitan Transportation Commission
Abstract
The Metropolitan Transportation Commission (MTC) carries out an extensive project performance assessment in support of our regional planning efforts. For our currently-in-progress regional transportation plan, projects were adjudged on qualitative and quantitative criteria. The quantitative criteria was a benefit-cost ratio in which a project’s expected annual benefits were compared to the project’s expected annualized cost. To quantify user benefits (one component of the total benefit estimate), we used the difference in build/no build destination choice logsums. The destination choice models include, as covariates, mode choice logsums, which means the change in destination choice logsums estimates the change in consumer surplus across all destinations and all travel modes. This approach has long been advocated for in academia, but it’s the first time – to our knowledge – that it has been used in a large-scale, practical multi-modal application that informs multi-billion (and smaller) dollar investment decisions. Our presentation will discuss the pros and cons of using this approach. The pros include the consistency between the simulated behavioral changes and the quantification of benefits, which cannot be achieved using more common measures of user benefits, such as travel time savings, as well as the ability to spatially locate travelers each project benefits and those each project harms (an invaluable debugging tool). The cons include issues related to the form and creation of alternatives in the mode choice model. Specifically, the addition or loss of a modal alternative may not always be a logical outcome of a project improvement but nonetheless reveal itself in the mode choice/path building procedures. For example, consider a mode choice model with separate bus and rail alternatives and a corridor in which bus and rail compete: if the project dramatically improves bus service, the rail route may not prevail when creating the rail-eligible path, which results in the rail alternative being dropped as a viable alternative which, depending on the size of the alternative-specific constant in particular, may result in illogical user benefit decreases.