That's the verdict from the Department for Transport (DfT), which has just released data from its LST evaluation project, which examined their impact in terms of efficiency, emissions and safety.
Trailers up to 2.05m longer than standard 13.6m units are of "no immediate concern", according to the DfT report, which states that LSTs have caused no increase in the rates of injury and that there had been no reported incidents resulting in serious injuries or fatalities.
"The incident data submitted under the requirements of the trial shows that these trailers are being operated safely and responsibly," comments FTA head of engineering Andy Mair.
"FTA is a supporter of the use of LSTs as they provide significant environmental and efficiency benefits," he continues.
"The report clearly demonstrates that operators in the trial are making significant efficiency improvements, reducing HGV miles and demonstrating carbon savings using LSTs on freight operations suited to their use."
The trial was launched in 2012, permitting up to 1,800 trailers in two length categories (up to 14.6m and up to 15.65m).
On average, the report says operators are saving one journey in 22, with some saving one in nine journeys.
Figures show that between 4.2 and 5.2 million vehicle kilometres have been saved from the operation of LSTs since 2012, leading to lower CO2 emissions.
Empty running for the LST was about 19%, compared with around 29% for the rest of the artic HGV data.
DfT hopes to involve more participants in the trial by the end of 2015 so the full allocation of 1,800 trailers is taken up.