The Slough experiment trialled the use of 20mph and 40mph speed limits, crossroad advanced warning signs and yield/give way signs (modern road signs shown).
The Slough experiment was a two-year road safety trial carried out in Slough, Berkshire, England, from 2 April 1955 to 31 March 1957. Different road safety innovations were tested to determine if they would reduce the number of road accidents. Amongst other innovations the experiment trialled the first linked traffic signals in the country, single yellow no-waiting lines, a keep left system for pedestrians and yield signs at junctions (the latter developed into the modern give way sign). The experiment also saw the first use of 20 mph and 40 mph speed limits in the UK. The experiment cost at least £133,100 and resulted in a 10% reduction in serious injuries and fatalities.
The British Government's Road Research Laboratory's (RRL) Traffic and Safety Division was established at Langley, near Slough in 1946.:2 The division was soon tasked with developing a new type of pedestrian crossing that would be visible in all weather conditions. These had previously been marked only by lines of metal studs across the road and poles on the footway at either side. Several different crossings were trialled in Slough from 1951 with the first zebra crossing being laid out on 31 October. The very first zebra crossing has since been lost as the road it was sited on was pedestrianised. RRL testing revealed that of all the crossings trialled the zebra crossing was the best solution and this was adopted for nationwide use.