The highest recorded number of longer semi-trailers are either on the road or will be soon, months into the fourth year of the government’s longer semi-trailer trial.

Latest figures from a report by Risk Solutions show that 91% (1,641) of the trial’s target of 1,800 trailers are registered on Vehicle Special Orders (VSOs). Of these, 84% are the longest available – 15.65m – with just 16% of the overall figure representing the 14.6m option.

The figures are a significant increase on those recorded earlier this year; as of February 2015, MT reported that just 1,439 of the allocated trailers were on the road or under construction.

The DfT said that it had allocated permits for all of the trial’s 1,800 trailers last autumn, meaning there are approximately 149 further allocations to be used.

The report before the full trial complement is on the road said that the average number of journeys saved by hauliers using the longer semi-trailers is one in every 22, with the highest recorded saving at one in every nine journeys.

Andy Dodge, sales director at Lawrence David (which has produced the highest percentage of longer semi-trailers to date, in collaboration with SDC) told MT the split was so wide between the two available lengths because the 14.6m makes less economic sense.

He said: “The 14m isn’t worth the cost involved. If you’re going to pay to take on a new axle you want to get as many extra pallets on it as possible.”

Dodge added that the company hadn’t taken an order for a 14.6m trailer since the government revised its structure of the trial in 2013, allowing operators more flexibility over what length of semi-trailer to use.

The FTA welcomed the report’s findings, pledging its support to the trial after the absence of any fatal accidents involving the longer trailers deemed their presence on UK roads to be safe.

Andy Mair, FTA head of engineering, said: “The incident data submitted under the requirements of the trial shows that these trailers are being operated safely and responsibly.

“The FTA is a supporter of the use of longer semi-trailers as they provide significant environmental and efficiency benefits. The report clearly demonstrates that operators in the trial are making significant efficiency improvements, reducing HGV miles and demonstrating carbon savings on freight operations which are suited to their use.”