Pity the proponents of the megatruck. These are the lobbyists, mainly from the road haulage industry, seeking approval for use on British roads of a new breed of heavy goods vehicle ten metres longer than a conventional pantechnicon, heavier than a Challenger battle tank, articulated in two places rather than one, and more of an undertaking to overtake than eight family saloons.

The official anagram for these road leviathans – LHV, for “longer, heavier vehicle” – is, at least, honest, and the government-sponsored study on their costs and benefits on which we report today is broadly positive. But as a decision looms on whether to allow a full-scale trial, opposition will be loud and persuasive. It will condemn road freight in general in favour of rail, and LHVs in particular as ill-suited to Britain’s congested motorways, myriad roundabouts and winding country lanes. They may be all these things, but only a trial will tell for certain. It should go ahead.

For all the Government’s pledges on integrated transport policies and climate change, most UK freight still moves by road. In 2005, the last year for which complete data are available, eight times as much freight travelled by lorry as by train in terms of billions of tonne-kilometres, and 16 times as much in terms of total tonnes lifted. Meanwhile, congestion in and between urban areas continues to worsen and road freight, on a mile-for-mile basis, has a carbon imprint three times heavier than the rail variety. If easing congestion and lowering national carbon output are priorities, shifting more freight from road to rail must be a long-term goal.

Yet this has been evident for years, and no Government or rail industry initiative has accomplished the shift. The reason was aptly, if inadvertently, summarised this month by Andrew Tinkler, chief executive of the Stobart haulage giant. High fuel prices had induced him to make greater use of the firm’s new rail freight subsidiary, but, he noted, “you [still] have to have a truck at either end”. Road freight offers door-to-door convenience, even for international loads. Using rail usually means at least three separate journeys within the UK alone. This basic difference explains the competitiveness of road freight, even in the age of oil at $100 a barrel, and it is a difference the LHV is designed to exploit.

Advocates of the new trucks, which are already in use in Scandinavia, present them as environmentally friendly and good for easing congestion. In a comparison with the use of rail (and nothing else), this would plainly be untrue. But if using LHVs can, in some cases, mean one truck instead of two, it may be worthwhile. With a new British device that steers an LHV’s rear wheels by computer instead of leaving them to skid round roundabouts, these monsters might also prove safer than the vehicles they replace.

High oil prices will continue to drive some forms of freight off roads and onto the railways more effectively than any government cajolery. But road freight will remain the backbone of Britain’s logistics infrastructure for the foreseeable future. The challenge for policymakers is therefore to minimise its impact on other road-users and the environment, not to try to eradicate it. The courage to think big must be part of this approach, starting with an LHV trial that enforces a strict low speed limit and a ban on overtaking and minor roads. A proper trial is not the same as blanket approval, and the fate of freight should not be left to guesswork.