Environmental speed limits : do temporary speed limits improve air quality?

Abstract

In 2004, Oslo introduced a policy that involved a temporary reduction in the maximum speed limit of 20 km/h (80 – 60 km/h) during the winter. The aim of this policy was to improve local air quality in order to reduce the adverse health effects related to air pollution. This master´s thesis analyses the effectiveness of implementing environmental speed limits on the choice of speed and local air quality in Oslo. We use an ordinary least square regression (OLS) and a regression discontinuity design (RDD) to perform a pooled cross section analysis on four air pollutants, PM2.5, PM10, NO2 and NOX, for two selected roadways during the period 2006 – 2011. Our estimates are based on hourly data from multiple monitoring stations and independent data sources. Our findings indicate a 5.8 km/h reduction in travel speed. However, there is no robust evidence of an improvement in air quality for any of the air pollutants. Our conservative cost–benefit calculation suggest that implementation of the environmental speed limits is associated with a net social loss of 4,120,000,000 NOK each environmental speed limit period. These findings suggest that the implementation and further expansions of the environmental speed limit policy is ill-advised and entails a loss to the society. The inefficiency of environmental speed limits suggest that other actions are necessary to improve local air quality in Oslo