Forecasting Modal Share and Ridership for Chicago Airport Rail Express: Integrated Approach to Data Collection, Model Estimation, and Model Application.

The Chicago Department of Transportation coordinated an investment grade study of a proposed rail service from downtown Chicago to OHare and Midway airports. The Airport Rail Express would be non-stop or limited stop, high amenity service. To support this work, Resource Systems Group (RSG) conducted airport origin-destination surveys and stated preference mode choice surveys. The origin-destination survey data were weighted to represent the air traveler markets at the two airports. The stated preference survey data were used to estimate the coefficients of nested logit mode choice models. Wilbur Smith Associates (WSA) used the mode choice models and the weighted trip tables from the surveys, supplemented by data from other sources, to forecast Airport Rail Express modal share and ridership. As part of the mode choice model development process, WSA reviewed the survey data, such as reported travel times to the airport, that were used during mode choice model estimation and compared them with data from other sources. This paper summarizes how the data collection efforts were undertaken, including design and administration of the two survey instruments, and the subsequent mode choice model estimation work. It explains the cooperative process undertaken by RSG and WSA to refine, re-estimate and finalize the mode choice models to ensure consistency between the often separate tasks of model estimation and model application. Finally, the paper presents the development of the Chicago airports access mode models and their application to forecast Airport Rail Express modal share and ridership. It includes a discussion of the results by market segment.