To ask Her Majesty's Government what assessment they have made, if any, of the effectiveness of the Masonry Arch Repair and Strengthening (MARS) system as a potential alternative to the infilling of railway bridges deemed unsafe by Highways England; and whether, as part of any such assessment, they have estimated the total (1) cost, and (2) reduction in carbon emissions, of adopting this approach instead of infilling.
23 July 2021
The Masonry Arch Repair and Strengthening (MARS) system is one of a range of treatments which is considered for the delivery of our maintenance of the Historical Railway Estate (HRE). It is a system that is suitable for strengthening and reinforcing masonry arches. However, given the type of structures that comprise the HRE, it can only be considered for a small number of arched structures. It should be noted that MARS is just one proprietary system and other systems are used where appropriate to undertake repairs on the HRE, examples include Shankend viaduct and Queensbury Tunnel.
It was considered as a treatment at Great Musgrave. However, Highways England’s assessment found that while initial costs were estimated to be lower than infilling (approximately £100,000 for MARS versus £125,000 for infilling), it would take longer to install MARS. Using the MARS system would also require much more follow up maintenance resulting in additional future costs. Those costs are estimated to be ongoing maintenance every 20 years costing approximately £15,000, major refurbishment every 60 years costing approximately £100,000, plus costs for detailed examinations every 6 years costing approximately £1,500. These additional costs do not apply for infilling, representing better value for money.
The carbon cost of the MARS system is difficult to estimate and compare. The steel used in the MARS system would have to be manufactured and transported to site, most of which usually comes from outside of the United Kingdom. The carbon costs would be far greater than sourcing fill material from a local quarry, although it is accepted that this carbon cost comparison does not take account of the fact that infilling might prevent use for cycling and walking unless an alternative route were provided.
At certain sites Highways England (HE) has partially infilled and provided an access for either active travel or heritage railways, for example three bridges in Cumbia on the Cockermouth, Keswick and Penrith branch for a heritage railway and in North Ayrshire on Route 73 of the National Cycle Network. Infilling whilst maintaining access is approximately 50% more expensive than infilling alone and requires ongoing maintenance and inspection costs. Where HE has completed this type of work it is on structures with existing or committed active travel routes.