You report (Oxford Mail, June 23) that the county council has voted in favour of a blanket 20mph speed limit on Oxford's roads.

Once again, county councillors are making traffic plans without considering the long-term effects - for example, on the already high pollution levels in Oxford streets.

A recent report by the AA found that cutting the speed limit from 30 to 20mph can increase, not reduce, CO2 emissions - because fuel economy is less and drivers have to use low gears.

The AA also found that speed humps increase fuel consumption.

Another factor our councils seem to ignore is that a lower speed limit will keep cars on our roads longer.

Such ill-advised schemes as Oxford's badly-designed Frideswide Square junction and Abingdon's £3m Abits plan increase tailbacks, which inevitably cause more pollution.

There may well be benefits to safety in lower speed limits, but these should be weighed up with awareness of the possible disadvantages.

TONY AUGARDE Carlton Road Oxford