Tunnel safety – an inventory of accidents in four road tunnels in Stockholm
This report investigates traffic accidents in four road tunnels in Stockholm. The tunnels investigated are Klaratunneln, Söderledstunneln, Törnskogstunneln and Häggvikstunneln. The main purpose of this project was to work with a delimited part of the project TUFS (Tunnel Framkomlighet och Säkerhet, Tunnel practicability and safety, my translation) that is going to build a knowledge bank for Swedish road tunnel accidents. The goal of this project was to investigate if the forecasts for accident rates in the tunnels calculated from empirical data differ from the forecasts of the road network made by the forecast program used by Trafikverket, Lill-EVA, for the observed tunnels. Another goal was to determine where accidents occur in the tunnels. In addition, two different tunnel types were compared in terms of accident rates. The tunnel types are located in: countryside (high speed, low traffic flows, no on- and off ramps) or urban center (low speed, high traffic flows, on- and off ramps). Accident data has been collected from the data bases STRADA and NTS and compiled in histograms displaying accident type, light conditions, the seriousness of the accident and number of accidents/year.
The results showed that there are no differences in accident rates calculated by Lill-EVA and empirical data for accident rate, serious accident rate and death rate. However, there was a difference in the results concerning light injuries. No difference was found regarding the two tunnel types.
Rear-end collision was the most common accident type in Söderledstunneln and serial vehicle crashes in Törnskogstunneln and Häggvikstunneln. Vehicles that got stuck in the tunnel entrance dominated the accident type in Klaratunneln. The majority of the accidents occurred in daylight.
The coordinate positions for the accidents showed that there was a concentration of accidents near the tunnel entrance in Klaratunneln, Söderledstunneln and Häggvikstunneln. This is not the case for Törnskogstunneln where accidents have occurred in the tunnel center.