Research short
Updated calculations could lead to longer, heavier freight trains and lower costs.
Jasmin CollierEditorial Content Manager, RSSB
Unlocking additional freight capacity could mean transporting more goods, opening up paths for more trains, and reducing overall emissions. And following the announcement of the UK government's target to increase rail freight by at least 75% by 2050, this is all the more important.
With that in mind, we recently explored coupler strength (how much pulling force a coupler can withstand) and tractive effort (the pushing or pulling capability of a locomotive) in freight. Gaining a better understanding of the current limitations and potential for improvement in these areas could pave the way for longer, heavier freight trains and help operators save thousands of pounds each year.
Until recently, coupler strength ratings―and, therefore, freight loading limits―had not been reviewed wholesale since the late 1960s. This means that freight operators may be keeping their loading limits lighter than necessary because current industry guidance does not reflect the capabilities of the stronger couplers now available on the market.
Our project ‘Guidance on limits of freight train trailing length as governed by coupler strength (T1256)’ looked at the engineering principles behind these historic loading limits. It uncovered three ways to improve the way trailing load limits and wagon length limits are determined:
standardising the reserve factor (factors of safety) across all traction ratings, which enables trailing load increases for more than half of the GB freight fleet
determining the extent and length of gradients on a given route to apply more accurate ratings
using our newly developed calculator—which accounts for sloping and curvature in each track section on a route—to optimise trailing load limits based on the actual gross laden weight rather than the maximum permitted weight.
Improving how we calculate loading limits could enable freight operators to run an extra four wagons per train, save up to £346,000 for each route per year, and reduce CO2 emissions by 2 tonnes.
To read ‘Guidance on limits of freight train trailing length as governed by coupler strength (T1256)’ in full, head to our Research Catalogue.
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Despite the introduction of new, more powerful locomotive types to the network over the past 30 years, freight operators might be running lighter trains than necessary based on historic loading limit calculations.
For our project ‘Guidance on limits of freight train trailing length as governed by tractive effort (T1302)’, we looked at gravity, curving, acceleration, and total mechanical resistances (the tractive effort required to overcome the aerodynamic and internal frictional resistances within the train). This helped us back-calculate the historic values and come up with a new, more precise way to set trailing load limits for existing and modern freight conveyance.
Adopting these new calculations and running longer freight trains is expected to significantly lower operational costs. For example, operators could see savings of more than £2,000 per return journey. This also has the potential to reduce congestion on the network by enabling fewer trains to move the same amount of freight.
Combined, these benefits may encourage more businesses to move their goods via rail rather than road and help freight achieve its ambitions for growth.
Our ‘Guidance on limits of freight train trailing length as governed by tractive effort (T1302)’ report will be published soon. To register your interest, head to our Research Catalogue.