Fleets will benefit if the Government goes ahead with plans to cut the national speed limit from 60mph to 50mph.

The Energy Saving Trust (EST) said the most efficient vehicle speed is typically between 45-50mph, with faster speeds greatly increasing fuel consumption.

"It's true to say for an average car the most economical speed is 50mph.

"However, the difference between 50 and 60 is very modest,” explained EST head of transport advice Nigel Underdown.

"What will be the biggest benefit is the reduction in overtaking.

"If you are on a 60mph single carriageway it is inevitable you will meet slower traffic and it's the acceleration and deceleration that really impacts on fuel consumption.

Therefore, a reduction in overtaking will provide the biggest benefit in terms of safer and more economical driving."

The Government is considering the new limit on single-carriage A, B and C roads in an effort to cut the high death toll on the rural network.

“There will be some in the driving lobby who think this is a further attack and a restriction on people’s freedom,” road safety minister Jim Fitzpatrick told The Sunday Times.

However, Paul Clark the minister with responsibility for rural and local roads distanced himself from Fitzpatrick’s comments.

He stressed to Fleet News that his department had not decided to introduce the new limit. “No decision has been taken,” he said

But he would not rule out that it is now on his department’s agenda.

The Department for Transport (DfT) is just weeks away from opening a consultation into the government’s next road safety strategy, which will shape road safety policies for the coming decade.

It is highly likely that reducing the current 60mph limit on the country’s most dangerous roads – single carriageway rural roads – will be an option ministers are already looking into.

These speed limits are “always under review” Mr Clark said.

“A decision will be made based on a background of safety, environmental and economic priorities.”

Road safety organisations are divided as to how effective a new limit could be.

“Just changing the speed limit will almost certainly have little or no effect,” said Adrian Walsh, director of RoadSafe.

“However, if you reduce the speed limit and employ clever engineering changes to a road’s design you will reduce the crash rate.”

Meanwhile, road safety charity Brake was unequivocal in its support, but stressed enforcement was key.

“Brake has been campaigning for several years for speed cameras to be installed on country roads and is pleased to note this could become a reality,” added Roz Cumming from Brake.

Rob Gifford executive director of PACTS – the parliamentary advisory committee on transport safety, said the move would be “tokenism” without additional investment in enforcement and education.

“Without the proper investment it is just a token gesture,” he said.

Properly enforced, the impact of a reduction from 60 to 50mph for fleets could be dramatic.

Not only will it go a long way to significantly reducing the number of at-work drivers killed every year on the roads, but it will help fleets cut costs and reduce emissions.

Dr Jillian Anable, senior lecturer at the University of Aberdeen and author of several papers on transport and climate change that have influenced DfT policies, said at a Parliamentary conference on road safety last week that forcing drivers to slow down will drive down emissions.

“Speed enforcement and emissions are closely linked,” she said.

“The relationship between speed and carbon reduction needs to be pushed.”

However, fleet manager Debbie Floyd is unconvinced: "I'm not entirely convinced that modern day engines would see much fuel economy in the reduction of speed limits, but it would in theory improve the stance on road safety.

"A bigger concern would be the education of drivers and potential additional points."

Graham Hurdle, managing director of e-Training World, is also unconvinced about the benefits.

Educating drivers on areas such as how to correctly approach dangerous bends would be more beneficial than just reducing the speed limit, which will introduce other dangers he says.

“Slowing down the speed limit on open roads will just lead to more people overtaking.

"Overtaking is one of the most of the dangerous manouevres a driver can make and more overtaking, by impatient drivers who choose to speed, could lead to an actual increase in collisions and KSI's (Killed or seriously injured) on rural roads,” he said.

“Speed is not the issue. Inappropriate speed is the issue - whatever road you are on.

"Education remains the only way to resolve speeding.”

Enforcement of a reduced speed limit will be key to its success, and this is where new technology comes in.

Geoff Collins, sales and marketing director at SCS, the country’s only supplier of average speed cameras, told Fleet News that it is possible to use its cameras to enforce limits across hundreds of miles of rural roads.

“In theory it is possible,” he said.

Indeed, it is already happening in Scotland where 50km of the A77 is monitored by a network of average speed cameras.

Since the cameras were installed and a major campaign launched to educate drivers, there has been a significant reduction in crash rates and of speeding.

Now, despite the distance of road covered there are only three speeding tickets issued a week.

However, installing average speed cameras across the entire rural road network would cost millions.

To cover a 10km stretch of road costs £400,000 of capital outlay and then £40,000 a year to maintain.

“I would be very surprised if average speed cameras were rolled out widely,” said Collins.

“Currently our equipment is only used on high-casualty stretches of road.”

However, there may be a more cost-effective solution to policing a new speed limit.

A new fleet of average speed camera vans is being developed, which are currently destined to enforce limits at temporary overnight roadworks.

There is no reason why these could not be used to ensure drivers obey a new 50mph limit.