Trief vehicle containment kerbs from Brett Landscaping have been specified to provide protection on bridges as part of Manchester’s major Metrolink project.
The proven quality of Trief – the only product of its type to be independently tested to the BS EN 1317-2 standard for road restraint systems – was instrumental in Brett Landscaping being chosen for use within Phase 3 of Metrolink, Manchester’s light rail system.
This project has seen the creation of around 60km of new tram lines to connect the city to outlying areas including Oldham. As part of this process, nearly 80 bridges have been refurbished, repaired or strengthened to provide a low-maintenance system with a minimum 50 year structural design life.
Safety was a critical element of the bridge design, with enhanced containment required to protect against the risk of vehicles crashing onto bridge parapets and potentially onto the tram lines below. While standard crash barriers have been used where appropriate, there were a number of bridges in the Oldham area with relatively narrow road access, where such barriers would be unduly intrusive.
Delivery partner Parsons Brinckerhoff helped the client Transport for Greater Manchester to review alternative containment methods and identified that safety containment kerbs represented an acceptable solution. “With road speeds across these bridges being no greater than 30mph, we could calculate the level of risk accordingly, and safety kerbs fitted the bill,” explains the company’s Mungo Stacy.
Even so, selecting a suitable containment kerbing system still required extensive research to find a well-engineered safety kerb that was proven to deliver the required standard of safety – and the unique credentials of Trief made it particularly attractive to the Metrolink team.
While the Trief system has delivered a high level of vehicle and pedestrian safety since its launch in 1963, Brett Landscaping was not content to trust to past achievements and set out to prove the credentials of the system by becoming the first kerb manufacturer to test its vehicle containment kerb against the rigours of the latest BS EN 1317-2 standard for road restraint systems.
The best-selling Trief GST2A Kerb was therefore tested by the Transport Research Laboratory (TRL) at their globally renowned test centre in Crowthorne. Not only did Trief become the first of its type to pass the rigorous BS EN 1317-2 standard for Road Restraint Systems, it did so with the highest available A rating for impact severity, whilst the containment level was determined as N1.
This proved decisive for Metrolink. “The fact that Brett Landscaping had successfully sought compliance with BS EN 1317-2, combined with its common usage by local highway authorities across Britain, ensured that Trief had the ideal credentials for this project,” confirms Mike Hann of Jacobs, who designed the bridge solution.
The 400mm-high Trief containment kerb, which has been installed between carriageway and footway at 18 bridges, works in three ways. In the first instance, it provides an obvious visual deterrent. Secondly, if the vehicle deviates from the carriageway, the 25mm upstand provides an initial physical warning to the driver that their vehicle is leaving the carriageway. Finally, if the driver does not take the necessary action, the Trief Kerb’s unique profile passively prevents the vehicle from mounting the kerb and guides it back onto the carriageway, without propelling it into other lanes of traffic.
Groundworks were completed by principal contractor MPT (a consortium of Laing O'Rourke, Volker Rail and Thales), who were impressed by the quality of the Trief solution from Brett Landscaping.
“Metrolink is a long-term solution to the transport needs of the Manchester region, so it is essential that we use durable, effective building products,” explains Adam Rawling of MPT.
“The decision to use Trief kerbs ensures the optimum balance between vehicular access and protection of the Metrolink infrastructure.”
“Brett Landscaping has been immensely helpful in helping us to devise our bridge protection strategy, both in terms of engineering know-how and customer support,” concludes Mike Hann.
“The use of Trief helped us to overcome key challenges on the bridges in question, in order to deliver a cost-effective and fit-for-purpose solution.”