The objectives of this paper are to present the SNRA policies on cost-effective safety measures, i.e mainly 2+1-roads with median cable barriers but also separated 2+2- and 4-lane roads and to summarize important results and findings from opened projects as yet, totally some 1000 km. In the 1990's almost 100 Swedes were killed and another 400 severely injured every year on the 3500 km network of 13 m wide two-lane roads due to the huge traffic load. This comprised 25 % of all fatalities and 20 % of all severe injuries on the 100 000 km state roads. The main problem on all two-lane roads was run-off and head-on accidents causing more than 70 % of all fatalities. The event process tended to be the same. The driver looses control for some reason and crashes against some obstacle in the roadside area or an opposing unlucky driver. The pressure grew on SNRA in the 90's to explore more cost-effective measures to improve traffic safety. The alternative 4-lane road (i.e. with full access control and 18 m crown width including a 2.5 m median) was introduced for new constructions in the mid-90's in the aftermath of a political intervention with the objective to replace motorways to decrease costs and environmental intrusion without jeopardizing traffic safety. In 1998, SNRA decided on a full-scale programme to improve traffic safety on six existing 13 m roads using low-cost measures preferably within existing right-of-way. The main alternative was the 2+1-concept (i.e. with a central overtaking lane changing permitted direction every 1.25 km with a separating cable barrier preferably within the existing width 13 m) estimated to eliminate 20 to 50 % of all severe link accidents. The design was soon judged to be a major success with now almost 1000 km opened. Traffic safety results for the 2+2-concept (i.e. to widen existing 13 m roads to 2 lanes in each direction separated with a cable barrier with a pavew width of 16 m) and the alternative 4-lane roads are so far more disappointing, being no safer than 2+1. The main results and findings up to the middle of 2004 are as follows: Level-of-service for normal traffic for 2+1-projects is better than expected with equal or better service at direction-nal flows up to 1 400 v/h with a capacity of 1500-1600 v/h in one direction, some 300 v/h less than for an ordinary 13 m road. Expected problems for emergency and towing vehicles and with blockages due to vehicle breakdowns have been handled without any major problems. Safety effects for 2+1 are even better than expected. The fatality rate is 0.0017 (fatalities per million axle pair km) based on 11 fatalities equal to the motorway rate and some 80 % better than the before situation. The reduction including severe injuries is 55 %. 110 km/h projects have 50 % higher rates of fatal and severe injuries than 90 km/h projects. The 2+2 cable barrier projects and the newly constructed 4-lane roads have, slightly surprisingly, no better safety performance as yet than the 2+1-alternative. Median cable barrier crashes are as expected extensive creating major work zone safety problems. Projects in northern Sweden with more snowy winter conditions and 110 km/h projects have significantly higher rates. Maintenance problems are less than expected with barrier repairs and stationary operations as major concerns. Socio-economic costs have increased with some 70 % or some 100 KSEK (1 US$ = 7 SEK) per km and year, 65 % of this being barrier repairs. Drivers and public opinion are very positive. (Author/publisher)
Abstract