Valuing the external consequences resulting from the choice of travel mode

Travel mode choice has a direct impact on the level of external consequences caused by urban transportation. This study aims to evaluate and compare the external costs of two common travel modes, namely private car and taxi, within an urban network located in northern Iran. Five categories of external costs including global warming, air pollution, noise pollution, traffic congestion, and accidents were calculated for each mode. Traffic parameters and geometric characteristics of the network were collected, and the unit cost of each pollutant was calibrated to Iranian economic conditions using the benefit transfer method and purchasing power parity index. Results indicate that the average external cost of traveling by private car is approximately 5.5 times higher than that of traveling by taxi. Air pollution accounts for the largest share (56%), followed by accidents (18%), congestion (13%), and global warming (13%). Replacing private cars with taxis, especially for single-occupant trips, can significantly reduce the external costs imposed on society.