Moving too obstructed? Geographic barriers and traffic delays in Helsinki

Abstract

I simulate over 84 000 potential private motor vehicle trips between pseudo-randomly chosen origins and destinations in the Helsinki capital region, combining data on geographic barriers (i.e., waterbodies, steep terrain and nature preserves), trip features and commuter flows. Using this novel dataset, I investigate the impacts of geographic barriers on trip outcomes, controlling for a set of trip, origin and destination characteristics. To address endogeneity concerns, I construct an instrumental variable to differentiate between the effects of policy choices and the effects of barriers on the shapes of potential trips within the area. I find that barrier intensity is highly correlated with increased travel distances faced by commuters on the road network. However, increases in geographically motivated detours are not associated with significantly higher travel times, and are associated with higher average speeds. Additionally, barriers are not found to have an effect on the distribution of commuter flows, nor is barrier intensity associated with meaningful increases in congestion. The results survive a number of alternative origin-destination sets, suggesting that despite facing extreme barriers due to its coastal location, the Helsinki capital region has successfully planned its transportation infrastructure around these barriers.