Utvärdering av nya hastighetsgränssystemet: effekter på trafiksäkerhet och miljö

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Arne Carlsson
Urban Björketun
Mohammad Reza Yahya

The Swedish Transport Administration estimated prior to the speed limit review that an increased or reduced speed limit of 10 km/h would result in an actual increase or decrease of 4 km/h for passenger vehicles. The change for heavy goods vehicles with or without a trailer, was estimated to be less. Based on the above assumptions it is estimated that 13.5 fatalities and 42 serious injuries could be avoided annually on the national road grid. In respect of environmental impact, it is estimated that carbon dioxide emissions would be reduced by 32,000 tonne per annum. Two different strategies were applied when studying what effect the altered speed limits have had on fatalities and serious injuries. Effects were estimated based on accident statistics from STRADA as well as by estimating expected effects according to assessed mean speed differences before and after introducing new signage. Expected traffic safety effects have been estimated according to the Power model. Results from observed STRADA records reveal that a total of 30 lives per annum have been saved on roads adapted to recently introduced speed limit changes, with a reduction of serious injuries of 26 per annum. Results by the Power model estimates 11 fatalities and 37 serious injuries less per annum. The total result from the STRADA outcome is similar to the outcome estimated by the Power model in respect of the sum of fatalities and serious injuries, although the distribution between fatalities and serious injuries differs. Lives have predominantly been saved on dual carriageways where speed limits were reduced from 90 km/h to 80 km/h with more than 70 per cent of saved lives belonging to this group. It is important to take into account when analysing the above results that the time since the change is limited. In order to gain more reliable results it would be advisable with a continued follow-up of fatalities and serious injuries. Any impact introduced speed limit alterations have had on the environment is based on actual changes in mean speeds showing that the carbon dioxide emission level has decreased by approximately 21,000 tonne per annum. The decrease is primarily due to the extensive speed limit reduction on dual carriageways from 90 km/h to 80km/h. Following the above speed limit reductions, the annual decrease of sulphur emissions is approximately 100 kg per annum and a 90 tonne per annum reduction in nitrogen emissions. The reason for the environmental impact being less than expected prior to changing the speed limits is that the average speed by road users changed slightly less than first estimated by the Swedish Transport Administration.

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