The Swedish Road Administration (SRA) initiated an experimental work during 2004-07 aiming at implementing variable speed limits (VSL) at six ruralintersections and carry out studies of effects. The intersection is situated on a 13-meters wide (single carriageway) rural road with a speed limitof 90 km/h. It is a T-junction with a west-bound right turn lane of the main road and a east-bound left turning lane. VSL was introduced to increase the observance of the speed limits in the intersection, improve the traffic safety and the accessibility. The speed limit through the intersectionwas 90 km/h before, but with variable speed signs it can be set to 70 km/h when a vehicle is turning either from the side road to the main road or vice versa. Different kinds of effects of VSL were investigated by before and after studies. The before study was carried out in autumn 2003, the VSL measures implemented in autumn 2004 and the after studies almost 8 months later. According to the results from the attitude study, VSL have made atroublesome rural intersection much better. Both effects of VSL, an increased possibility to turn to the main road and better observance of the speed limits, have been fulfilled. A majority of the drivers state that it has become easier especially to turn to the main road. Some drivers did however feel an uncertainty about the approach speed of the cars on the main road. Fewer drivers were exceeding the speed limits since the VSL were introduced and the drivers claimed they had more respect for the VSL than the ordinary speed limits. Incoming traffic from the side road (1065 vehicles/day) results in VSL 70 km/f activation 530 times per day during 44 secondsin average. That means around two vehicles per period. The active time per day is hence ca 6.5 hours. Also the 500 left-turning vehicles from the main road activates the lower speed limit. The measured speed reductions with application of the traditional power model results in 0.067 fewer severe injuries and kSEK538 yearly in reduced accident costs. Compared to the expectations in the feasibility study, the effects are around twice as great. The number of dead and seriously injured road users is expected to halve by introducing VSL in the intersection of Fogdarp, which of course is a very good and promising outcome.ûWith high demand on equipment and centralcontrol it seems however that the costs of the variable speed limit will be too high. Savings in construction and operating costs are therefore necessary and work has therefore started to investigate various possibilities. The final profitability can therefore not be estimated in the current stage of the project. For the covering abstract see ITRD E135582.
Abstract