66 | New Scientist | 21/28 December 2019Figures suggest that roundabouts are more
efficient, too, allowing a greater number of
drivers through than a signalled intersection,
and reducing harmful exhaust emissions
from vehicles idling at a red light. “It’s really
one of those great win-wins in terms of both
the safety and the ability to keep people
moving,” says Shaw.
The UK has certainly taken to roundabouts
with abandon. A concrete number is hard
to come by, but the country has something
northwards of 25,000 of them, more than one
for every 16 kilometres of paved road. These
include bewildering classics such as Swindon’s
“Magic Roundabout” (pictured, below), which
is actually five interlocking roundabouts
arranged in a giant circle. It divides the
travelling public between awe and fear.
Since 2003, the UK’s Roundabout
Appreciation Society has even produced books,
calendars and other assorted memorabilia
featuring roundabouts with particularly
pleasing displays in the middle. “They lift
our tiring spirits on long journeys with their
colour, their inventiveness, with whatever goes
on the roundabout,” says Kevin Beresford, the
society’s president. Its 2019 “Roundabout of the
Year” is in Truro, Cornwall, and features giant,
wooden sculptured hedgehogs (pictured, right).
For all the FHWA’s technocratic enthusiasm,
such ardour is hard to find in the US. And yet the
US was a pioneer: the world’s first formal one-
way gyratory system was probably Columbus
Circle in New York (pictured, above right),
built in about 1870. Many other grand-scale
“rotaries” were built in the US in the following
decades, says traffic engineer Lee Rodegerdtsof Kittelson & Associates in Portland, Oregon,
who is an international authority on
roundabouts and keeps a database of those
in the US and elsewhere. So what changed?
“What happened is the circular intersection
fell out of favour here as a lot more automobile
ownership took over,” says Rodegerdts.
Early roundabouts also had a simple but fatal
flaw: traffic entering them had priority. This
is still the case in some corners of Europe and
sets up natural conflicts with already circling
traffic that are solved by a lot of weaving.
As traffic speeds and volumes increased,
the size of roundabouts were increased to
allow more space for this weaving, which in
turn encouraged higher speeds, and so on.
“It just kind of fed itself,” says Rodegerdts.
“It was basically a dead-end solution.”
The answer came in 1966 from an iconoclastic
British engineer called Frank Blackmore at the
UK’s Transport Research Laboratory. It seems
obvious now: you reverse priority to make
entering traffic yield to circulating traffic, and
gently curve the approaches to the roundabout
to make traffic slow down. This principle could
be made to work on intersections of all sizes.
It led Blackmore to pioneer a further
innovation: the mini-roundabout. “It’s such
a simple invention, isn’t it?” says Beresford.
“Just a painted blob in the middle of the road.“ Early roundabouts
had a fatal flaw:
traffic entering
them had priority”
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