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Roundabouts
in the UK
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first roundabout was constructed in Paris around the Arc de
Triomphe in 1901. According to the BBC the first "recognizable
modern roundabout" was New York's Columbus Circle. The first
British roundabout was five years later, in Letchworth Garden
City in 1909 - originally intended partly as a traffic island
for pedestrians. However, the widespread use of roundabouts
began when British engineers re-engineered the traffic circle
in the mid-1960s and Frank Blackmore invented the mini
roundabout to overcome its limitations of capacity and
for safety issues. Unlike traffic circles, roundabouts operate
with yield control to give priority to circulating traffic
and eliminate much of the driver confusion associated with
traffic circles and driver wait associated with junctions
that have traffic lights. Roughly the same size as signalled
intersections with the same capacity, roundabouts also are
significantly smaller in diameter than traffic circles, separate
incoming and outgoing traffic with pedestrian islands and
therefore encourage slower and safer speeds |
Some of Several UK Roundabout Signs. More Signs
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Roundabouts
are safer than both traffic circles and traditional intersections—having
40% fewer vehicle collisions, 80% fewer injuries and 90% fewer serious
injuries and fatalities (according to a study of a sampling of roundabouts
in the United States, compared with the intersections they replaced).
Roundabouts also reduce points of conflict between pedestrians and
motor vehicles and are therefore considered to be safer for them.
However, roundabouts, especially large fast moving ones, are unpopular
with some cyclists. This problem is sometimes handled on larger
roundabouts by taking foot and bicycle traffic through a series
of underpasses.
Movement
within a roundabout in a country where traffic drives on
the left.
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Mini
roundabouts
Mini-roundabouts
exist at smaller intersections to avoid the use of signals, stop
signs or the necessity to yield in favour of one road of traffic.
Mini-roundabouts can be a painted circle, a low dome, or often
are small garden beds. Painted roundabouts and low domes can easily
be driven over by most vehicles, which many motorists will do
when there is no other traffic, but the practice is dangerous
if other cars are present. Mini-roundabouts work in the same way
as larger roundabouts in terms of right of way. They can often
come in "chains", making navigation of otherwise awkward junctions
easier. There are usually different road signs used to distinguish
mini roundabouts from larger ones.
In the UK the maximum diameter permissible of a mini-roundabout
is 4m. Whilst it may be physically possible, it is illegal for
vehicles like cars, which can turn around the mini-roundabout,
to go over the painted island, or around the wrong way- vehicles
should treat it like a solid island and proceed around it. (In
practice, few motorists obey these rules). Some local authorities
have installed double white lines around the island to indicate
this, but these are not permissible. The centre island also must
be able to be over-run by larger vehicles. If this is not possible,
perhaps due to plants, or street furniture it is considered a
small roundabout not a mini roundabout and as such must adhere
to the stricter roundabout guidelines
A slightly larger version of a mini-roundabout, sometimes called
a "small roundabout", is designed with a raised centre surrounded
by a sloped "overrun area" of a different colour from the roadway
and up to a meter in thickness called a "truck apron" or a "mountable
apron". The truck apron's design discourages small vehicles from
taking a shortcut over it while at the same time allowing the
mini-roundabout to more easily accommodate the turning radius
of larger vehicles (such as a truck which may have to navigate
the roundabout). These are not well suited for bus routes, as
mounting the apron can be somewhat uncomfortable to passengers.
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