Suppressing the effects of induced traffic in urban road systems: impact assessment with macrosimulation tools - results from the city of Krakow (Poland)

Abstract This paper presents results from simulation analysis of road network development scenarios in the city of Krakow (Poland), accounting for potential impact of traffic demand elasticity. These envisage a completion of a suburban ring road, which would improve network travel conditions and could therefore induce additional traffic volumes (and eventually lead to further traffic congestion). The objective was to investigate how this effect might be inhibited by introducing complementary changes in the city road network, ranging from individual road narrowing schemes in the city centre to “bolder” measures comprising network-wide traffic calming and road closure scenarios. Our macrosimulation-based analysis reveals that, once accounting for demand elasticity phenomena, city-wide benefits are roughly similar for all the considered scenarios, but a durable traffic congestion relief could be only achieved with a consequent reduction of inner-city network capacity. Our findings indicate how the appraisal process of urban road projects could be facilitated with an estimate of potential demand elasticity effects, as effectiveness of such schemes needs to be assessed not just in terms of level-of-service improvements, but also their exposure (or resilience) to erosion in scheme benefits due to probable induced traffic phenomena.