Estimating the external costs of travel on GPS tracks

Providing people with information on the external costs of their mobility, including generated emissions and congestion, has been shown to influence travel behaviour. We present a methodology for estimating transport externalities at the link level on GPS data, with the aim to provide more accurate estimates of external costs. Emission values for various pollutants are calculated for each link using the HBEFA database, accounting for vehicle type, road category and traffic conditions. For congestion, average link delays are computed for each hour of the day. We apply this methodology to GPS trips collected during a national mobility pricing study. The methodology is validated against the Swiss national estimates. The range of per-kilometer values for various external costs are compared to the Swiss norm values. The observed trip-level heterogeneity in per-kilometer external costs supports the hypothesis that using average values in the analysis of external costs is insufficient.