The challenge
In the 1990s, 13-metre-wide two-lane roads made up 3,500 km of Sweden's 100,000 km of national roads but saw 25% of road deaths and 20% of serious injuries; head-on and run-off crashes caused more than 70% of the deaths on them.
The case
In 1998 the Swedish Road Administration started a development programme, called 'collision-free roads' from 2002, to make existing 13-metre roads and semi-motorways safer in a cost-effective way, with much lower investment costs than traditional measures. The roads were redesigned as 2+1 roads, with an alternating sequence of two lanes in one direction and one lane in the other and a barrier between the two directions of travel. The first median barrier was put up in summer 1998 as a pilot on a stretch of road with many fatal accidents; the test was greeted with considerable scepticism but proved to work extremely well at avoiding head-on collisions. Between 1999 and 2016 about 400 km of semi-motorway and 2,500 km of two-lane roads were converted. A 2009 evaluation found that fatalities on 2+1 roads decreased by 77%, and fatalities and serious injuries by 51% on 110 km/h roads and 63% on 90 km/h roads, with no major change in all injury crashes. The safety level of 2+1 roads was about the same as for motorways. Average car speeds rose about 2 km/h at the 90 km/h limit, and crashes into the median cable were fairly frequent.
Why it worked
The evaluation compares the roads before and after conversion, so it shows a strong association rather than a randomised result. The Swedish Transport Administration reports about 50 fewer people killed every year on these roads, and lists 2+1 roads among the key interventions of its Vision Zero road safety policy.
Sources
- Vadeby, A. Results – Safety benefits of implemented measures. Swedish National Road and Transport Research Institute (VTI) presentation, hosted by Trafikverket.
- Carlsson, A. (2009). Evaluation of 2+1 roads with cable barriers: final report (VTI Rapport 636) (TRID abstract).
- Trafikverket, Vision Zero Academy (2020). Median barriers.
- Trafikverket, Vision Zero Academy (2019). Key interventions based on Vision Zero.
- Löfqvist, Å. Road safety measures on Swedish roads. Trafikverket presentation.
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