Are current Norwegian speed limits optimal? : a quasi-experimental analysis of changes in speed limits on Norwegian freeways

The aim of this paper was to examine if Norwegian speed limits on freeways could be more efficient from a social economic standpoint. We examined the relationship between regulations in speed limits and actual speed held by vehicles on Norwegian freeways, as well as looking at how this regulation changes the magnitude of traffic. With these estimations of relationship, we sought to estimate actual benefits and costs of a change in speed limit from 110 km/h to 120 km/h by analyzing the change from 100 km/h to 110 km/h and apply this to a potential change from 110 km/h to 120 km/h. There are few studies on this topic in Norway and seeing, as this is a very hot topic politically in Norway today, we found this study to be of interest. With hourly counting data for two Norwegian freeways, we analyzed the effect of a change in the speed limit from 100 km/h to 110 km/h on actual speed change and change in traffic magnitude. With these results, we wanted to see if it would be economically efficient to increase the speed limit further from 110 km/h to 120/km on Norwegian freeways. Based on a sharp regression discontinuity design (RDD) analysis of the increased speed limit on freeways E39 Skoger and E6 Kløfta Sør we found that only smaller vehicles benefits from the increase in speed limit, when it comes to time saving. Other vehicles are observed to be given no time savings, as these vehicles are restricted in Norwegian law to drive no faster than 80 km/h. For smaller vehicles, an increase in the speed limit from 100 km/h to 110 km/h resulted in an increase in observed speed between 2.59 km/h and 2.93 km/h. With an increased maximum speed limit from 110 km/h to 120 km/h we get an increase in the average speed held by drivers from 110 km/h to 113 km/h in the left lane and from 101 km/h to 104 km/h in the right lane. We saw no direct effect on the traffic magnitude on the roads of the higher speed limit, but we observe an increasing trend. Utilizing our estimates for actual speed increase and traffic magnitude from the impact of an increase of maximum speed limit to 110 km/h, we try to evaluate the economic impact of a further increase to 120 km/h. To determine the economic effect of a further increase in the speed limit, we used a cost-benefit analysis and sensitivity analysis on actual speed increase and the effect of using our estimated value of time. We found that per year, people save on average 232 NOK with a speed increase of 3 km/h. With a cost-benefit analysis of a further increase in the maximum speed limit from 110 km/h to 120 km/h on existing freeways, running sensitivity analysis on actual speed increase, with no change in observed traffic magnitude and change in time value, we estimate that the total social economic effect of this shift varies between 280 MNOK and 1694 MNOK