Magic Roundabout (Hemel Hempstead) a New Town the roads met in a simple junction which was then replaced by a standard roundabout. Constructed in 1973, the "Magic Roundabout" in Hemel Hempstead was voted the UK's second-worst roundabout in a 2005 poll held by an insurance company (the winner being its Swindon counterpart). In 2011 the roundabout was voted the best in Britain by motorists in a competition organised by a car leasing service. The original magic roundabout had six exits in total, with the British Petroleum building spanning "Marlowes", the road leading to the town centre, in the approximate position of the earlier railway
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