A timber guardrail for highways made with hardwoods

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Abstract

A timber guardrail made of sustainable tropical hardwoods has been developed in the Netherlands. The guardrail is an environmentally friendly alternative for zinc-coated steel barriers. The guardrail is made of a combination of two durable hardwood species: angelim vermelho (Dinizia excelsa) from Brazil and azobé (Lophira alata) from Africa. Full-scale tests have shown that the guardrail is able to withstand the impact of a 13000 kg bus driving at a speed of 70 km/h and an impact angle of 20° as well as that of a car of 900 kg having an impact speed of 100 km/h and same angle. Steam bent curved boards are used as energy absorbers from the passenger car impact. After the full-scale tests with the bus, no damage was found in the timber elements, and the guardrail had only to be straightened, saving repair costs during the service life of a guardrail. The guardrail fulfils the requirements specified in European standard EN 1317 Road Safety Systems for the H2 level with accident severity index of 1.0.