Research found that one in five drivers broke the 20mph limit by 10mph or more

Almost nine in ten motorists drive too fast on 20mph roads. A study by the Department for Transport found that 87 per cent of car drivers exceeded the limit last year.

The research, carried out using automatic traffic counters, found that 22 per cent of drivers broke the limit by 10mph or more. Researchers urged caution with the findings, saying that many of the roads listed would be “through routes” rather than residential streets more typical of 20mph zones.

Nevertheless the conclusions will cast doubt on the wisdom of converting hundreds of miles of urban roads into 20mph zones in place of the previous 30mph default limit in towns and cities.

It follows the publication of a major evaluation by the Department for Transport (DfT)