Longer Semi-Trailer Trial

Longer-semi trailers (LSTs) allow more goods to be transported at once, allowing operators to reduce the number of lorries on the road for the same total quantity of cargo.

DfT are trialling use of these new trailers on roads in Great Britain and Risk Solutions have been retained since 2012 to carry out the independent evaluation of the trial.

The 2017 annual report was launched on 19 September 2018 at an event attended by representatives of the companies running LSTs and a wide range of other stakeholders.


The report shows that at the end of 2017, there were almost 2,000 LSTs on the road and they had covered 443 million km. 85% of their journeys are on Trunk roads (Motorways and A Roads operated by Highways England) 13% on Principal roads (A roads operated by local authorities) and 2% on Minor Roads. This is a similar split to the standard GB semi-trailer fleet.

These LST trips have saved in the region of 225-270,000 HGV journeys with an average saving of 1 journey in every 14. The most efficient operations achieve a saving of 1 journey in 8.

The reduced number of trips has resulted emissions savings of around 7% – equating to around 28,000 tonnes of CO2(e) and 141 tonnes of NOx.

After 6 years of the trial, we have a statistically robust analysis to show that they are being operated safely, with an injury incident rate only around one third of the average for the trailers they replace, even when operating on minor roads or in urban areas.

Next steps

The trial is now moving on to look at further areas of interest including, damage-only incidents, the performance of different types of steering axle and most importantly, the types of operational requirements that are needed to maintain the good performance seen on the trial.

Further information:

The full annual report and separate summary document can be found on the Department for Transport’s website at www.gov.uk/government/collections/longer-semi-trailer-trial#progress-reports.

Trial participants can send any enquiries related to the data collection aspects of the trial to Risk Solutions on 01925 413984 or at LSTTrial@risksol.co.uk

Any enquiries not related to the data collection or analysis should be addressed directly to:
Philip Martin
Head of Freight Policy, Freight, Operator Licensing and Roadworthiness Branch


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