In the highway code and the law courts, there is no doubt what those big numbers in red circles mean. As a quick trip up any urban street or motorway with no enforcement cameras makes clear though, many drivers still regard speed signs as an aspiration rather than a limit.
Technology that will be required across Europe from this weekend may change that culture, because from 7 July all new cars sold in the EU and in Northern Ireland must have a range of technical safety features fitted as standard. The most notable of these is intelligent speed assistance – or colloquially, a speed limiter.