The Red Flag Locomotive Act
The increasing popularity of the ‘horseless carriage’ in the late 19th century meant that in highly populated metropolises such as London, where there was genuine concern that these new-fangled contraptions would cause fatal injuries, there was a definite need for new rules and regulations. Between 1861 and 1898 a number of Locomotive Acts were put into place, but that of 1865 was undoubtedly the most bizarre.
'The Red Flag Act', as The Locomotive Act 1865 became known, required that self-propelled vehicles, or automobiles, travel at no more than 4mph in the countryside and no more than 2mph in cities. Furthermore, such vehicles must have a 'crew' of three people - one of which had to walk 60 yards in front waving a red flag (or carrying a lantern) to warn people that the automobile was coming.
So, basically, one could travel in an automobile so long as one travelled the precise speed one would travel by foot…
[Sources: Image | Locomotive Acts | Red Flag Traffic Laws]