The speed issue

Ever since those 19th century pioneer drivers were forced have a man walking in front of them carrying a red flag, speed on the roads has always been a big issue.

Things eventually relaxed in the UK, of course, and it wasn't until 1967 that speed limits were introduced on the motorway. Now, the issue of speed is once again highly topical, since the government is consulting on raising the motorway speed limit from 70mph to 80mph, a change that could happen as early as 2013. If the UK government goes ahead, it could echo the US state of Texas, which is tipped to introduce an 85mph speed limit on one of its toll highways.

Socialvoices: all cars should be limited to 80mph

Of course, it's highly unlikely that we'll ever follow Germany and scrap motorway speed limits altogether - although the Isle of Man has unrestricted speeds on its out-of-town roads - but with The Speed Issue very much in the spotlight, we thought we'd ask some speed-related questions.

Why can modern cars achieve speeds so far in excess of the speed limit and how do manufacturers justify it?
Motorway speed limits vary widely across the world, from just 62mph in Japan, 70mph in the UK, 81mph in France and Italy up to no limits at all on German autobahns.

What top speed a car can do is usually frankly irrelevant where there's a speed limit in place. Even basic city cars are capable of topping 100mph these days, which is way over the national speed limit. But city cars don't behave like larger cars on motorways: at 70mph, their engines can be spinning at 4,000rpm - which gets pretty uncomfortable for passengers and is pretty inefficient on fuel. Compare that to, for example, a current Corvette, which has a top speed of 190mph, yet at 70mph is barely ticking over at 1,500rpm. Lower revs at motorway speeds mean better fuel economy and a more relaxed drive.

Why it's time to raise the motorway speed limit

What would the advantages/disadvantages be of limiting all cars to 70mph?
Electronic speed limiting is very easy to do. Indeed, many new cars already have a speed limiter that can be set by the driver to warn them when they exceed a certain speed limit. Many sat-nav systems can also identify what the speed limit is and warn the driver about it, so it would be easy to limit cars to 70mph in the future.

In fact, there's already a case of one country where all cars are speed-restricted by law: in Japan, they're all electronically limited to 140kmh (87mph).

There's an argument that a forced 70mph limit would make traffic flow better, as the differences in speed on motorways would be less, so cars would brake less. That would likely lead to lower accident rates - even though motorways are already statistically the safest roads to drive on. Also a lot less fuel would be used: the IAM estimates that sticking to 70mph rather than 80mph saves around 4p per mile for a typical car.

And the disadvantages? Journey times would be longer for many drivers, which would have an impact on the national economy, and many people who drive for a living could end up working very long days.

There's also the situation where the safest way to avoid an accident is actually to accelerate out of danger. And doing 75 or 80mph for a short time to overtake a slow car may actually be safer than sticking to 70. Hitting a 'barrier' at 70mph when accelerating in real-world scenarios could compromise road safety.

And what about if you had an emergency, and needed to get a loved one to hospital in a hurry? How would you feel with a life in your hands if your speed were restricted to 70mph on a clear, open motorway?

Celebrity speeders exposed

How would insurance companies look upon drivers who voluntarily limit the speed of their cars?
Some insurance companies already offer the option of putting a 'black box' recorder in your car. Using GPS technology, this records all sorts of information including, speed, distance travelled, time of day the car was driven, location and braking data. The reason to have this black box fitted is simple: it can reduce insurance premiums. This applies especially to younger drivers, but equally to anyone who can build a picture of safer driving - particularly female drivers who are seeing their historically lower premiums than men rise in the wake of sex equality rulings. Many insurance companies charge lower rates if a driver can show they are following speed limits regularly.

Speeding police officers exposed

Is technology to limit the speed of cars likely to be forced on us in the future?
All the necessary technology is already in place for speed controls to be fitted to cars, should such a scheme become mandatory. Indeed, a trial has already taken place in Australia, where GPS devices were fitted to 100 cars, warning their drivers when they went too fast; if they persisted in exceeding the speed limit, the device then limited the supply of fuel to the engine, forcing the car to lose speed.

Will these GPS speed limiters ever become reality, though? Isn't it all a bit too 'Big Brother'? Ultimately it's up to our elected government to decide, and we know that governments have been looking at this issue for some time. Our best guess is that, for now at least, there seems little prospect of it happening in the near future.

22 of the UK's fastest-speeding motorists