Structural design and pilot-scale trials of modular cellular paving for greened safe havens and emergency access routes

In order to reduce congestion on the motorway network, the Highways Agency (HA) aims to create additional road space without road widening by turning some hard shoulders into extra traffic lanes. This objective raises safety concerns associated with the parking of broken down vehicles that would need to be left on strengthened verges or towed to purpose built safe havens. In a parallel initiative, the HA aims to improve emergency access to, and egress from, the trunk road network through the provision of emergency turnaround areas in the road verge and other escape routes. The HA commissioned research into the possible use of grassed, cellular pavers to surface such areas on the road network, as they provide a less conspicuous refuge for unauthorised users. A range of pavers was reviewed and six systems were identified and tested for strength and fracture mode in laboratory tests. Design traffic was predicted and the maximum static load applied by propped trailers when disconnected from their tractors was determined. Pavement designs were formulated and two examples of concrete modular systems were built and tested in TRL’s pavement test facility. The pavements were trafficked by up to 50,000 standard axles with a rolling dual wheel and loaded statically by a 10 tonne load simulative of a propped axle of a trailer. Despite some deterioration of the pavers, the pavements remained serviceable suffering little deformation and thereby validated the designs as conservative. The research demonstrated that, providing appropriate engineering standards are developed, grassed, cellular systems should provide a viable surfacing for safe havens and for emergency access and egress routes. Road trials under typical environmental conditions are recommended to further develop paver and foundation specifications, pavement design and to select vegetation that can survive these difficult conditions without degrading the pavement’s functions. (A)


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  • Accession Number: 01050765
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Jun 5 2007 12:06AM