Magnitude of mode constants in transit mode choice

This study aims to improve the calibration procedures in mode choice modules for transit ridership forecasting through better understanding of calibrated mode constants representing unmeasured inputs. In this study, the magnitude of mode constants is examined by relative importance to measurable components of mode choice utility, using data from Philadelphia and Washington DC. In the case of walk-access modes, the mode constants in study cities account for about 41%-65% of total utilities. The results demonstrate that, in some cases, mode constants are large enough to render models insensitive to changes of important but omitted factors such as reliability, comfort, access environment, and safety. This study provides some evidence on what portion of travel cost between an origin and a destination is comprised of a fixed mode constant. By applying the approach, it is useful to identify problematic segments that have unusually large mode constants.