Magic Roundabout
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A Magic Roundabout, officially known as a Ring Junction, is a type of junction design consisting of a ring of mini-roundabouts, enabling traffic to pass around the junction either clockwise or anti-clockwise. In effect, the inside track (closest to the centre island) of a ring junction travels anti-clockwise.
History
Ring junctions were a natural progression from the development of mini-roundabouts and double mini-roundabouts in the early 1970s. The first example of a ring junction was built in Swindon in 1972, with the Plough Roundabout in Hemel Hempstead being converted from a conventional roundabout in 1973. Other examples have followed.
Operation
Whilst superficially they look like a conventional roundabout, their operation is very different, and should be treated as a series of linked mini roundabouts rather than a single large junction. They have a much larger capacity than a standard roundabout, but have the disadvantage of being confusing to drivers who have not previously encountered them. It can be quicker to travel anti-clockwise around the island as intuitively more traffic will choose to travel clockwise.
They are efficient in handling large numbers of turning movements at a junction because there is a choice of vehicle paths around the junction. Opposing right turns have no conflict with each other, compared with other junction forms.
Depending on the size of the magic roundabout and the number of circulating lanes, the central island can be relatively small, for example the one in Swindon which is almost completely covered by roadway, with only minimal use of a central island. In other examples, for example at Hemel Hempstead, there are fewer circulating lanes around a larger central island.
Magic Gyratories and other variants
Magic Roundabouts are related to Magic Gyratories, which are functionally identical but consist of a ring of full-size roundabouts, though these may not be obviously different in use. Another development of a magic roundabout can be seen at Denham Roundabout (M40 Junction 1), which comprises four full sized roundabouts around the two-way gyratory, plus signal controlled junctions with the A40 and M40 slip roads.
Examples
Magic Roundabouts can be found at the following locations:
- Greenstead Roundabout, Colchester
- Magic Roundabout, Swindon
- Abbey Way Gyratory, High Wycombe (can be seen as a Magic Gyratory)
- Plough Roundabout, Hemel Hempstead
- Hatton Cross Roundabout, Heathrow Airport
The former magic roundabout at Sadlers Farm has now been replaced.
Links
Roads.org.uk
