Born in Algeria on 16 February 1916 to a British father and Swiss mother, Blackmore studied civil engineering in Lausanne, Switzerland. He came to Britain in 1936 to work in the borough engineer’s department at Colchester Borough Council.
After a 20 year sojourn as an RAF pilot during and after the Second World War, Blackmore joined the government’s Road Research Laboratory (RRL), today known as TRL, in 1960 and it was here that his interest in roundabouts emerged.
With no rule for giving way to traffic circulating a roundabout from the right, free-for-alls would often ensue, causing junctions to lock up and massive queues to form on the approaches.
A growing campaign for vehicles approaching the junction to give way at a stop line was championed by Blackmore and the rule was written into Department for Transport guidance in 1966. The new system had an immediate impact on reducing road accidents and improving traffic flow.
The challenge was then to design a version of the roundabout that could be applied in thousands of constrained urban settings where there was a lack of space to install a conventional roundabout.
Blackmore’s controversial solution, developed at the RRL, was a smaller roundabout with a 2-4m wide mini island in the middle that minimised the curve for the vehicle driving around it. This aided traffic flow and was arguably safer because drivers approached it with more caution.
The new roundabout design first appeared in Peterborough in 1969 and was formally written into government design manuals in 1975.
By this time his experiments had become increasingly radical. Among these were the "Magic Roundabout" in Swindon in 1972 and multi-ring junction in Hemel Hempstead in 1973. Such junctions comprising as many as six mini-roundabouts – like a series of cogs in a piece of industrial machinery – did cause some chaos when first encountered by bewildered motorists.
But Blackmore proved that the multi roundabouts reduced speed, increased throughput and aided traffic flow.
Blackmore officially retired from his TRL post as scientific officer in 1980 and carried his crusade overseas as a consultant in Bangkok, Baghdad and California.
He died on June 5, 2008.