Supporting detail:

Trialling longer HGV semi-trailers

The Department for Transport (DfT) started a trial of longer semi-trailers (LSTs) for longer articulated goods vehicles in January 2012, with a total allocation available of 1,800.

The trial involves longer semi-trailers of 14.6 metres and 15.65 metres in length (17.5 metres and 18.55 metres total vehicle lengths respectively). Longer semi-trailers should provide significant economic and environmental benefits to the UK. The operational trial is a real opportunity for industry to show the benefits these trailers can bring to the UK. The trial is expected to save over 3,000 tonnes of CO2 over 10 years. The overall benefits are estimated at £33 million over 10 years.

The longer semi-trailers must operate within the UK’s existing domestic weight limit (44 tonnes for vehicles of 6 axles). Participation in the trial is on a voluntary basis and at the participants’ own risk. DfT doesn’t provide any guarantee that the use of the longer semi-trailers will continue to be permitted beyond the end of the trial period. The trial is scheduled to run for a maximum of 10 years, to help enable participants to recover the costs of their investment in the longer semi-trailers. Further information about the trial features in the following pages:

Data requirements and trial evaluation

DfT’s trial of longer semi-trailers is a research project which has been established to evaluate and understand the use of these vehicles. The usage and performance of all of the longer semi-trailers in the trial is being monitored and evaluated by DfT’s contractors, Risk Solutions. When operators apply for longer semi-trailers, they are agreeing to take part in this research project and are making a commitment to collect data on their use of the trailers and submit it regularly to Risk Solutions throughout the trial. The following page explains the data requirements in more detail:

The Department appointed Risk Solutions in 2011, experts in strategic risk management, to independently monitor the trial. Risk Solutions are monitoring, among other things, the impact of the longer semi-trailers on carbon emissions, lorry miles and accident rates. They are producing regular reports.

Risk Solutions will be able to answer enquiries from trial participants related to the data collection aspects of the trial. Any enquiries not related to the data collection or analysis should be addressed to the Department for Transport.

Please email all general trial queries to and all data queries to

Issue of VSOs for longer semi-trailers

Operators using longer semi-trailers will need to apply to the Vehicle Certification Agency (VCA) for Vehicle Special Orders (VSOs) which legally allows the operation in commercial service of the longer semi-trailers.

It is the operator’s responsibility to ensure that they obtain a VSO covering all of the longer semi-trailers that they use on the road. VCA will inform DfT when it issues a VSO to an operator.

Any longer semi-trailers operating without a VSO are operating illegally and may, for example, invalidate any insurance policies covering their use. While it is not a legal requirement, operators may find it helpful to make sure that a copy of the VSO covering the longer semi-trailer is carried in the cab whenever that semi-trailer is in use.

In order to obtain a VSO, operators must have signed the undertaking to the effect that they will:

  • present the longer semi-trailers to Driver and Vehicle Standards Agency for annual roadworthiness testing
  • provide data to Risk Solutions for the purposes of monitoring the trial
  • ensure that drivers are appropriately trained
  • inform the Department for Transport immediately if a longer semi-trailer is involved in a serious accident

The secondary market

Once they have obtained the longer semi-trailers, operators will be free to purchase the vehicles from each other (the allocation quota moving with the vehicle). The new operator would have to apply for the necessary VSO.

However, operators must notify the department with their intention to purchase a longer semi-trailer from another operator to ensure that they meet the allocation criteria, as outlined in our guidance document.

The allocation itself has no monetary value and must not be bought or sold. Only the vehicle can be bought or sold.

Northern Ireland and Europe

The trial applies only to roads in Great Britain. Operators who wish to go over to Northern Ireland in their longer semi-trailers must contact the Department of the Environment Northern Ireland (DOENI) to obtain an additional VSO at

The longer semi-trailers do not comply with standards in force in other European member states so cannot be used for international traffic in mainland Europe.

Moving vehicles between sites for trial or demonstration purposes

The Road Vehicle (Authorisation of Special Types) (General) Order 2003 permits longer trailers to be used on public roads for ‘tests and trials’ purposes, without needing a VSO.

No prior authorisation from the department is required as long as the use is in accordance with the requirements and conditions set out in the order. Section 38 covers requirements as to length. One of the conditions is that the vehicle is un-laden. Another is that the police should be given 2 clear working days’ notice.

For those companies who hold an ‘O’ licence, the ESDAL (electronic service delivery for abnormal loads) system provides a web-based notification facility.

Manufacturers who do not themselves hold an ‘O’ licence should contact their local police force’s abnormal loads officer, who should be able to advise on the notification procedure.

Schedule 11, Part 2 of the order gives a more precise definition of what is meant by tests or trials. It defines this term as including the use of vehicles or trailers for demonstration purposes. However, only a court can provide a definitive view of whether a particular activity fits the terminology used in the legislation, so if manufacturers are in doubt they should seek legal advice.

Background information