On speed

On 29 September, Phil Hammond, the then Transport Secretary, proposed increasing the speed limit on motorways to 80mph. We’ve been here before. In 2002, the Commons Transport Select Committee looked at raising the limit but decided against the move because it would result in a 5-10% increase in casualties on motorways. We may as well, mayn’t we? After all, Department for Transport figures show that as many as 49% of drivers currently flout the current 70mph limit. But on the other hand, road safety charity Brake claims a move to 80mph would see speeds on Britain’s motorways pushed ever higher.

Higher speeds would lead to more accidents, and more serious accidents. Remember v2 = u2 + 2as and E = ½ mv2 from your school physics? Stopping distances increase according to the square of your speed. Likewise the energy of a collision. The Association of British Drivers says despite the UK’s motorways being significantly busier than other European motorways, there are far fewer fatalities. It seems to me that setting lower speed limits, in order to keep traffic flowing on busier roads (e.g. on the M25), could well be the reason that fatalities are lower.

Seven people died in the terrible multiple pile-up on the M5 near Somerset, and 51 people were injured. If Justine Greening, the new Transport Secretary, goes ahead with the increase in the speed limit, so this sort of event becomes more likely, I wonder how she would sleep at night. And then if – when – it happens again, how will she look the families of the victims in the eye?

But of course, the policy is not about road safety. It is about increasing tax revenues, a ‘stealth tax’ if you like. Most cars are most fuel efficient at a speed between 40-60 mph. Supposing a car has its highest mpg at 55 mph, then it will be 17% less efficient at 70 mph and 28% less efficient at 80 mph, i.e. will use 15% more fuel for the same journey at 80 mph than at 70 mph. That’s 15% more fuel duty revenue into the Treasury coffers. It will be needed to fund the extra cost to the NHS and emergency services.

It’s also a 15% increase in carbon emissions, at a time when we urgently need to reduce them.

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