The average speed at which motorists feel it is reasonable to drive above the legal limits includes 26mph in a 20mph zone and 79mph on a motorway, a poll of more than 2,000 UK adults revealed.
Direct Line Car Insurance, which commissioned the research, also found that more than three out of four drivers (78%) admit to speeding, with 5% speeding on every journey they make.
Asked why they speed, half (51%) claim they do not realise how fast they are travelling, while a third (34%) deliberately speed when the road is empty.
Some 19% speed when they are running late and 14% do it when there are no speed cameras.
There were 229 deaths on Britain's roads in 2016 in collisions involving a speeding vehicle, Department for Transport figures show. A further 1,549 people were seriously injured.
Rob Miles, director of car insurance at Direct Line, said: "Speeding is one of the biggest causes of accidents and casualties on UK roads.
"The research suggests it is often not deliberate, as drivers may be unaware they are creeping above the limit.
"However, speed limits are set for a reason and 20mph and 30mph zones are often around schools, hospitals and other highly pedestrianised zones, where going over the limit could prove fatal in the event of an accident."
A spokesman for road safety charity IAM RoadSmart said: "Sadly, IAM RoadSmart are not surprised by these findings as our own research suggests that the majority of drivers are happy to break the limit on motorways. What is new, and more worrying, is to see similar figures for urban areas.
"Drivers need to take more personal responsibility to avoid becoming one of the millions caught every year. A speeding conviction should never be considered the