One of your readers recently asked why car manufacturers can't restrict all vehicles to Britain's national speed limit of 70mph (Letters, March 31).

It's very difficult technically for motor manufacturers to do. There are two reasons: Firstly, the engine has to rev at a higher speed to be able to reach the national speed limit.

Secondly, if the engine's revs are restricted by fuel/ignition systems, the vehicle will grind to a halt when driving up the smallest gradient with a heavy load in the back.

A low-revving engine can put out more power only if the cubic capacity is raised. This will increase pollution and it will cost more to insure the car.

In the EU, many cars are fitted with speed limiters. They are restricted to 155mph. This sounds high but it does deliver a good, economic power band for everyday driving.

The best way forward is to educate drivers as to where and when they can use the power of a vehicle safely. Maybe your reader would prefer us all go back to travelling by a horse and cart?

  • Ian Hunt, Pavilion Road, Worthing