I HAVE used a number of speed detector devices from the cheap to the most expensive units on the market but have yet to discover how they improved my driving ability.

Although dashboard detectors are able to detect roadside and mobile laser cameras as well as radar devices they are susceptible to various forms of enforcement such as police Vascar (distance over time) and the forward facing infra red systems, as well as the fixed motorway units like those over Thelwall Viaduct. Satellite devices are similar in what they do not detect infra red sites unless they are already in the database that the unit refers from to enable it to issue its warning.

Satellite based systems also do not detect mobile laser cameras nor police Vascar, so total "protection" from speed enforcement devices, even if both devices are purchased, is impossible. Also, false alerts are a major problem especially in built-up areas and as far as using them on approach to a camera site to determine a loaded camera then it is possible for the device not to work until the last second.

It is easier to visually check your speed but as Mr Sadler (LET, Letters) describes, taking your eye off the road for three seconds equates to 132ft at 30mph. There is growing evidence to suggest that more accidents are becoming attributable to this paradox so maybe a little more discretion and more balanced approach on behalf of the authorities might work.

With strict enforcement a good example should be set from the authorities where driving is concerned, particularly from these enforcing the speed limit. Parking dangerously to conduct speed checks sets a bad example as I witnessed on the A59 at Billington a few weeks ago where an enforcement van was parked half on the grass verge and half on the carriageway, blocking the mandatory cycle lane and forcing goods vehicles to slow in order to pass it!

Going to such extremes to criminalise otherwise respectful and law abiding people for nothing more than the supposed fear of danger where there is no real accident rate (and no pedestrian danger) than for any scientific reason only lowers respect for the police, since it is the police who are seen as the enforcer, banning the use of speed detection devices further widens the gap between police and those drivers who use such devices as a driver aid.

IAN TALBOT, Radcliffe, Manchester.