One of the country's largest transport firms has called for speed limits on lorries using some roads to be increased - on safety grounds.

The delivery company TNT, which has its UK headquarters at Atherstone in Warwickshire, wants HGVs using A roads to be legally allowed to travel at 50mph.

The present limit for HGVs is 40mph and 60mph for cars.

It has been backed by the Freight Transport Association and the Motoring Trust in its claims that heavy vehicles travelling too slowly relative to general traffic cause congestion and pose risks for motorists who try to overtake.

But the Department for Transport dismissed any changes. A spokesman said: "The subject has been raised. There are no plans for change."

TNT's director of operations, Nigel Barton, said he believed raising the limit for HGVs would lead to smoother traffic flows and reduce motorists' frustrations.

"We are not necessarily saying the HGVs should be treated exactly the same as smaller vehicles on single carriageway 'A' roads, but the limit should certainly be increased to 50mph. This would go some way to helping traffic move more freely," he said.

A high number of fatalities take place on 'A' roads in rural areas. Many of these are caused by reckless overtaking.

Figures from the Department for Transport show that in 2004, the latest full year statistics available, there were 81 fatalities in rural parts compared with 69 in more built-up areas of the West Midlands.

The respective figures categorised as killed or seriously injured (KSI) were were 500 and 701.

Mr Barton said advancements in vehicle engineering would help reduce accidents.

"With advancements in braking and suspension systems, modern day HGVs are extremely well equipped to handle increased speeds in rural areas, without incurring any heightened accident risk," he said.

Bert Morris, director of the AA Motoring Trust, welcomed the suggestion of changing A road speed limits and said modern trucks' braking speeds were much better now.

Chrys Rampley, manager of infrastructure for the Road Haulage Association, said a change would help ordinary motorists as well as lorry drivers.

"We have been advocating the same thing. Motorists get very frustrated - they chance it to overtake. But if lorries keep up with the traffic, then you don't get this." * Paramedics used lassoes to round up a truckload of pigs running loose on a motorway yesterday after a crash caused them to escape.

Amused motorists stuck on the M6 took snapshots of the impromptu "pig rodeo" as the air ambulance crew attempted to haul in the animals.

Warwickshire and Northamptonshire Air Ambulance (WNAA) were asked to help capture the pigs after they escaped on to the southbound carriageway of the motorway near Rugby, Warwickshire.

A WNAA spokeswoman said its crew had already been called to an earlier accident on the northbound carriageway.

As they circled above, a land ambulance crew told them they were no longer needed but they then received a call to the nearby accident involving the pigs.