two designs of post and rail bridge parapets have been developed which provide more positive containment of vehicles and better vehicle response after impact than conventional parapets. in one design the posts fracture at their bases at a predetermined transverse loading thereby minimising the rolling motion of a large vehicle towards the parapet. in the tests both a car striking at 116 km/h and 20 degrees and a coach striking at 82 km/h and 20 degrees exhibited the same steer back response towards the parapet after impact. the car weighed 1488 kg and the coach 5194 kg. maximum wheel penetration of the coach was 0.79 m. in the second design the posts yield, bending at their bases under impact from a large vehicle but are not damaged by car impacts. in the tests a coach striking at 86 km/h and 20 degrees was redirected at 13 degrees to the parapet with a maximum wheel penetration of 0.36 m. a car striking at 109km/h and 20 degrees was steered back to the parapet after impact. details of the designs are available from the the transport and road research laboratory as follows: frangible post parapet: drawing no.sg.1040.21/a, yielding post parapet (cranked post): drawing no. sg.1040.19/a, yielding post parapet (straight post): drawing no.sg.1040.26/a (a)

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