The UK Government's announcement that it is considering raising the motorway speed limit to 80mph came rather out of the blue. It smacks of a populist measure, and the arguments behind it should be treated with some suspicion.

We can accept, as has been said, that car technology has advanced beyond most people's imagining in the 1960s when the 70mph limit was first enacted. At the same time, however, so has the volume of traffic on the roads. Car braking and safety features are not the only factor in the accident statistics.

And is it just my impression, or is there a lot more aggreessive driving these days? Additional power under the bonnet can esily translate into a temptation to throw one's weight around.

That leads to what is surely the weakest ground for arguing for a rise - the claim that as, it is said, many otherwise law-abiding drivers disregard the 70 limit, the law is out of step and we should therefore change it to legalise people's habits.

What tripe. Would the minister also use such an argument to raise the drink driving limit if it was being regularly ignored? Not likely. Proceeding on such a ground would have the opposite effect to increasing respect for the law, as it would encourage the idea to take hold that relaxation could be achieved by going on pushing at the limits. It is naive to think that an accepted tolerance, if such it currently is, of 80mph before police action is taken, would not quickly become 90 if 80 were the official limit.

I would be loth to see average speed cameras on every motorway, but perhaps the minister should look to the evidence of the M77 and their effect on cutting the accident rate there, if I recall correctly, before declaring that higher speeds would not increase the accident rate.

I don't usually stray into economic arguments, but since they too are being invoked in the argument - even though the lorry limit does not appear to be under review - let's look at those too. On a 200 mile journey, assuming the ability to drive at the legal limit all the way (and how often does that happen?), the difference in journey time between 70 and 80 mph is just over 20 minutes. How much would that boost GDP? It would get a bigger boost if you took the train instead and did some work on the journey.

Perhaps the Government is eyeing up the extra tax revenue from people burning up the extra fuel they would need to go faster. In which case it would blow any green credentials they claim, out of the water.

The arguments of the supporters of change on Question Time last night only strengthened my view that this is a thoroughly bad idea, and one to be resisted.