Background 

In 1998, on an arterial road south of Gothenburg, Sweden, the Swedish National Road Administration (SNRA) had a problem. On this stretch of road - which serves 25,000 vehicles per day and has a speed limit of 90km/h - there were 2 - 3 fatalities each year. The SNRA decided to implement what they now commonly call 2+1 roads. 2+1 roads are similar to our overtaking lanes here in New Zealand; 2 lanes one way, 1 lane the other. In the median however, they installed a wire rope barrier to prevent head-on accidents. 

The Safence™ median barrier, now installed on more than 300km of Swedish roads, has effectively eliminated head-on collisions.

The median barrier used was a Safence 3 rope system with a post spacing of 2.5m. Under NCHRP350 test conditions*, this would give a deflection of about 2.2m; under European Standard EN1317 test conditions**, a deflection of 1.7m. 

At the time, these deflections were considered inappropriate for the median. The SNRA weighed up the pros and cons - on one hand they could virtually eliminate head-on accidents but on the other there was a risk that a vehicle would deflect the barrier and impact an oncoming vehicle or an accident would block the lane. The SNRA decided to trial it. They now conclude that the benefits far outweigh the risks. This was very unconventional thinking at the time.

* 2000kg pick-up truck at 100kph at a 25 degree angle
** 1500kg vehicle at 110kph at a 20 degree angle
 
Results 

After 5 years and the installation of more than 300 km of wire rope on 2+1 roads of similar and higher speeds, the SNRA have concluded that deflection is not the issue it was once perceived to be. Since this installation, there have been no accidents where a vehicle has deflected the fence in a way that could have caused a collision with an oncoming vehicle.  

The key results for the entire 2+1 roading programme since 1998 have recently been documented by the SNRA. They are: 

• Safety results are better than expected
• Maintenance problems are less than expected
• Drivers attitudes to the new concept are very positive
• Emergency and towing companies are complaining about reduced workloads

For more information go to www.vv.se, the homepage of the SNRA.