Roundabout constructed in 1972 in Swindon, Wiltshire, United Kingdom, designed by Frank Blackmore, inventor of the mini-roundabout. The roundabout joins five roads and consists of a two-way road around the central island, with five mini-roundabouts meeting the incoming roads. The name derives from the popular children's television series, "The Magic Roundabout", and is considered "magic" because traffic flows in both clockwise and anticlockwise directions. This is achieved by surrounding the main island with one smaller roundabout per entry/exit street. This pattern directs traffic in the usual clockwise (in LHT installations) or counter-clockwise (in RHD installations) manner around each mini-roundabout. Exiting the
Roundabout islands is 28 metre diameter ICD with a 4-metre diameter island. This threshold being driven primarily by vehicle geometry – which is globally relatively consistent – rather than driver behaviour, it is adopted in other jurisdictions too. Below this minimum size, the mini-roundabout prevails. After developing the offside priority rule, Frank Blackmore, of the UK's Transport Research Laboratory, turned his attention to the possibility of a roundabout that could be built at sites lacking room for a conventional roundabout. Mini-roundabouts can be a painted circle or a low dome but must be fully traversable by vehicles. Motorists can drive over