Barrier separated road type design: accelerated degradation

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To reduce the risk of vehicular head-on collisions, the Swedish Transport Administration (Trafikverket), has been transforming high traffic-volume conventional roads into barrier separated roads. This process has reduced the number of fatalities by around 80 percent.

However, evidence has shown that barrier separated roads degrade quicker than conventional road types.

The extent of the problem was quantified by comparing various sets of road surface characteristic data. Comparisons revealed that degradation levels increase by up to 60 percent in the single lane sections of 2+1 type barrier separated roads.

Vehicle position surveys were carried out and subsequent data analysis confirmed that confinement of vehicle lateral wander is a main cause of the problem. The analysis indicated that in the single lane section of a 2+1 type barrier separated road, vehicle lateral wander reduced by 24 percent for light vehicles and 19 percent for commercial traffic. These figures increased to 44 percent and 39 percent for a 1+1 type barrier separated road.

Accelerated degradation can be attributed to poor cross-sectional design. The amount of vehicular lateral wander is restricted and results in surface wear and loading being concentrated in narrow tracks along the road section.

Design improvements are possible but will obviously require higher initial investment expenditure.

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