State of the art of concrete safety barriers

In 1976 the ~ew Jerey concrete safety barrier and the experience gained internationally with it was for the first time brought to the attention of interested persons in highway authorities, research and industry in the Federal Republic of Germany. Four years later, the first pilot projects were implemeneed in this country. Others were to follow. In response to the favourable experience that has been gained with them, concrete safety barriers have since been installed in most of the Bundesländer (Federal States), and the trend is distinctly upward. The Federal Ministry of Transport has established criteria for their construction, taking account of experience both in Germany and in other countries. In the new code of practice for passive safety devices, recently prepared, concrete barriers are for the first time included in a German set of technical regulations. Concrete safety barriers prevent vehicles from leaving the carriageway, protect the occupants of vehicles from collision with roadside obstacles or falling from embankments and give protection to persons or installations by the roadside. Barriers are especially advantageous on narrow central reserves and dividing strips, at local narrowing of the clear width beyond the carriageway edges, on busy roads and for the protection of noise reduction barriers. The Federal Institution for Roads (Bundesanstalt für Strassenwesen) explicitly recommends the provision of concrete safety barriers in front of noise reduction barriers in certain cases. The space between the two barriers is preferably planted with vegetation. Concrete safety barriers are almost invariably constructed in situ by slipforming.For this technique, the concrete should have a very uniform consistency and the highest possible "ereen" compressive strength •. It should moreover be highly resistant to the action of frost and de-icing salts. The barrier is supported on the carriageway pavement itself or on a foundation installed at frose-free depth. Sawn dummy joints serve eo prevent cracking. The experience gained with concrete safety barriers is generally rated as good, though in some isolated cases they have been rejected. Experience shows that they favourably affect road safety under the conditions encountered in Germany, too: there is a distinct reduction in road accidents, injuries, deaths and damage to property; in one case a barrier even prevented an army tank from plunging off the road. There has been very little need for awkward and expensive maintenance and renewal work, not even on anti-dazzle devices fitted to the barriers. The effectiveness of the barriers was nearly always preserved even after collision with vehicles. Combined action with noise reduction barriers has proved advantageous. Also, it has been found that concrete safety barriers, besides having a protective function, provide good visual guidance for motorists, especially at night.