Simulation-based assessment of double-parking impacts on traffic and environmental conditions

The objective of this research was to estimate the effects that a specific pattern of illegal parking (double-parking) had on traffic conditions and the environment by using microscopic simulation. Through a sensitivity analysis, the effects of illegal double-parking on average speed, delay, and stopped time were estimated. Results showed that the existence of the phenomenon entailed a severe decrease in average speed and an important increase in delay and stopped time. Through a case study, the effects that a reduction or an elimination of the phenomenon would have in a real network were evaluated: all traffic indicators would be improved if double-parking were suppressed partially (e.g., through an intensification of enforcement) or, even better, completely. Results showed that limiting double-parking could result in an increase in speeds of about 10% to 15% and a decrease of about 15% and 20% in delay and stopped time, respectively. However, even greater improvements may be achieved if double-parking is eliminated: average speed can increase by up to 44%, while delay and stopped time can decrease by up to 33% and 47%, respectively. On the basis of the results extracted from the case study, the effects for the whole district of the municipality of Athens, as well as for the entire Athens region, were assessed by using several indexes and performance measures. Savings from decreased lost time and reduced carbon dioxide, carbon monoxide, and hydrocarbon emissions were calculated. Directions for future research are also proposed.