/ Motoring

What’s the real cost of an 80mph speed limit?

The increased 80mph motorway speed limit debate has raged here on Which? Conversation. But now the proposition for the 10mph increase has been hit with a new stumbling block…

The Road Safety Foundation (RSF) has stated this week that England’s motorway network just isn’t up to coping safely with an 80mph traffic flow.

According to its report, the RSF said existing motorways in the country do not offer enough protection to drivers and car occupants if the limit is increased. There would, it says, be an increase in the number of shunt crashes and there currently isn’t enough prevention to stop drivers running off the road.

Concerned by reduced fuel efficiency

But my long standing issue isn’t just with the effects on road safety, as motorways can always be rectified and improved. Instead, it’s the financial burden of an 80mph limit on motorists’ wallets that has concerned me.

According to the AA, two thirds of its members support the speed limit increase. But have these drivers looked into the efficiency pitfalls of this, which are clearly presented on the AA’s site? It says that ‘cruising at 80mph can use up to 25% more fuel than at 70mph’.

And we already know that fuel prices are one of the key issues crippling consumers’ bank accounts at the moment. According to a recent survey from car valuation firm Glass’, as many as 38% of motorists said they would give up driving entirely within a year if prices at the pumps continue to rise.

Mileage matters on motorways

But with fuel efficiency being severely impacted by a motorway speed increase, drivers are ultimately going to get less mileage out of the fuel they’ve taken onboard.

And if people become more concerned about the extra 10mph eating away at their miles per gallon (mpg) figures, there could be serious safety repercussions with motorists lowering their speeds  to achieve a better return when the majority of traffic is moving at 80mph.

You can use our fuel economy calculator for an accurate interpretation of what an individual car’s mpg is. But for now, we want to know if the reduced fuel efficiency of an increased motorway speed limit would be an issue for you?


Even if the speed limit gets upped to 80mph, there’s nothing forcing people to drive at that speed if the don’t want to. If they’re driving a shed, can’t afford the extra fuel or whatever they can still drive at 70 or 55 (just as long as they don’t hog the overtaking lane)

I wonder if anyone has done any research on what %age of people in fact drive above the 70 mph limit now. Chances are its the same roads and the same people so all an 80 limit might mean is no speeding ticket for actually doing the same speed.

John Symons says:
17 May 2012

I agree. If some drive at 80 mph there has to be an unprecedented degree of lane discipline if less wasteful drivers are to drive safely, although it is clear that many drive at more than 70 or even more than 80 already. I doubt whether this proposal could be combined with other ideas such as allowing the hard shoulder to be used. There is also an increased risk of or greater impact from collisions with birds, deer, etc

Daz says:
17 May 2012

Absolute rubbish (RSF) as most drivers break the speed limit now anyway so the increase in the limit would do nothing to change the status quo.


Any decrease in fuel efficiency is counterbalanced through an increase in time efficiency. However, an increase to 80mph will only legalise what most drivers already do and which many police forces already turn a blind eye to. Coupled with a speed limit increase, as others have said, we definitely need a new specific offence of “driving in an overtaking lane without overtaking”.


Not sure I agree entirely with the increase in time efficiency counterbalancing the reduction in fuel efficiency – I don’t see how arriving somewhere quicker will save you money in most cases?

And if you truly believe there’s currently a blind eye turned to travelling at 80mph on a motorway, do you think this will increase to 90mph if the limit is upped?


Time efficiency is not only about saving money; it’s also about reducing time wasted while driving at an unnecessarily slow speed, resulting in increased time to other more interesting or productive tasks before and after a journey. Compare our low motorway speed limit with other European countries, most of which have fewer lanes and some of which have greater traffic densities.

Some police forces tolerate up to 90mph already, provided that the driver’s conduct is otherwise perfect. I doubt there would be any change in the current enforcement approach.


My employer charges me out to clients at £175 an hour, so IN THEORY spending an hour more with the client and an hour less in the car would earn my employer £175. But in reality…

The time saving, i.e. the costs involved, are trivial. On a typical journey I’d save no more than 15 minutes from an increase in the speed limit.
The amount of work I do for the client is usually fixed, so it just means I start and finish a little later.

The argument that “Many people break this law” is feeble. If murder were to become commonplace would that be an argument to repeal the laws on murder?

Driving in an overtaking lane without overtaking, whilst very annoying, creates no danger to other road users in the vast majority of cases. And if it did, I’m sure it will be covered by existing motoring laws. So there is no need for a specific offence, an offence which would be difficult to define precisely and difficult to enforce.


I wish the Cumbrian police could take a commonsense veiw of “speeding”. I was charged with doing 80mph on the M6 at Tebay while overtaking a slower vehicle, and it was very quiet that morning. I wrote a letter to the cheif constable explaining the circumstances, but received a letter back from his underling giving no ground for any excuse whatsoever. There is a place for “speed camera” vehicles but not on the top of motorway flyovers that are only there for revenue and nothing to do with road safety.



Do you really expect the Chief Constable to reply personally and explain that there is no excuse for breaking the law?

Just pay up, infor