Longer, heavier vehicles (LHVs) could reduce the carbon footprint of many transport operations in the UK.
According to Professor Alan McKinnon, from Heriot-Watt University, who was speaking at the Freight Transport Association Carbon Conference, the use of LHVs (pictured) could cut carbon emissions because they are more efficient.
"But the risk is since they are cheaper to operate, they could encourage freight to shift from other modes."
He adds that because it is a very controversial area, he doesn't expect to see 34m trucks running in the UK, but the door is still open to run a trial of longer semi-trailers that could carry six extra pallets. "A 
lot of companies want to take advantage of that," he says.
Jim York, conference chairman and head of engineering special projects at DHL Exel Supply Chain, says: "There needs to be an open door on LHVs, and we need a concerted industry view - possibly channelled through FTA."
Other areas McKinnon touched on include carbon labelling, biofuels and the Euro standards.
Talking about carbon labelling on products, which many of the big supermarkets are keen on, McKinnon says: "Transport is only small element; the main thrust is carbon in the production process.
"Because New Zealand produces lamb in a very energy-efficient way, even though it has to travel 18,000km, it still has a lower carbon footprint than lamb produced in this country. We can't shop our way out of climate change."
However, 
he believes that reducing the carbon impact of transport is more achievable through more fuel efficiency and efficient transport operation than biofuels.
McKinnon also points out that the Euro-6 particulate emissions regulations produce a 2-3% CO2 emissions penalty. "Maybe the time has come to re-prioritise these objectives and put more emphasis on cutting CO2."