The 70 limit was introduced in 1965, in response to a spate of serious accidents on the motorway network. The accidents that triggered the move were in foggy conditions, and it is hard to imagine how a theoretical speed limit would stop people who were happy to drive at that sort of speed in thick fog, but then logic has never been the strong suit of those in charge of the transport network. Of course, the limit had to be introduced for all roads, otherwise you would have the ridiculous situation of the motorways having a lower limit than a country lane. It's amazing to think it now, but before 1965 you could drive at any speed you wanted as long as you were out of a built-up area. This situation still obtains in the Isle of Man, of course. The killjoys haven't got round to that yet.
Another reason for the introduction of the limit was that AC Cars were caught testing the prototype for the Cobra at 196 mph on the M1. This was obviously not acceptable to Transport Minister Barbara Castle (a non-driver), an early example of that curious state of mind amongst our elders and betters that if it is fun, it must be stopped. Can you imagine the Italian police round Maranello stopping all the Ferrari test drivers and asking them to be a bit more careful? Round there, the locals come out and line the streets and would be disappointed if the drivers didn't put on a bit of a show. The thought of hamstringing an iconic Italian manufacturer by petty 'safety' regulation wouldn't enter their heads.
The 70 limit was introduced with very little debate. As most family cars could barely exceed that speed in 1965, I suppose it seemed a reasonable measure. Is it still reasonable? The engines, brakes, handling and passive safety of even the most humble hatchback far exceed the technology available 45 years ago. There aren't many cars that can't cruise comfortably at 90 mph, and in fact from the motorway driving that I do it seems that the default speed for most people is around 80 in clear conditions. I think there is a good case for increasing the limit to 80 or even 90 mph. In fact, there is a good case for removing the limit altogether, and applying limits according to need - see my post on speed limits in Germany. I wrote:
I have a theory. In Germany, on much of the autobahn network, there are no speed limits. People are trusted to make their own decisions about how fast they go. When there is a reason to do so, speed limits are imposed, in a sensible way, and removed as soon as they are not needed. Because of this, German drivers seem far more prepared to observe speed limits than British drivers are. They recognise that they are there for everyone's benefit, and used in specific circumstances, rather than as a blanket control measure designed to take the fun out of motoring and raise some cash from the motorist at the same time. I didn't see a single speed camera or traffic patrol car in Germany, and yet the compliance with speed limits was far higher than in our camera-infested country.But of course that will never happen - at least, not under any current version of Labour (red, blue or yellow) that has the chance of being in government in the foreseeable future.
Would increasing or even removing the current limit increase pollution through the slightly higher fuel consumption of vehicles travelling 10 mph faster? Probably not: the improvement in traffic flow would probably cancel that out. Would it increase the number or severity of accidents? I doubt it. Motorway accidents happen generally because of poor driving habits in general and poor lane discipline in particular, and seem to me to bear little relation to speed.
Go and tell the IAM what you think, or leave a comment here. Or both, of course.
UPDATE: as before, the IAM site isn't letting me access the poll page. Keep trying.