William Eno’s early small US circles (1920s-1930s) were called the “Sleeping

Policeman,” “Dummy Cop,” and later Ohio’s “Mound.” The designs were not

traversable, so they quickly resulted in fixed object collisions, and none

survive today.

Frank Blackmore’s traversable “miniroundabout” was the solution, but it only

became possible after enactment of the offside priority rule (yield to the

left) that Frank himself had championed (1966).

The term "Miniroundabout" was coined 40 years ago by Frank Blackmore

(1916-2008) at the UK Road Research Laboratory, circa 1968-69. His first

traversable mini was built in 1970, and his standard design was adopted in

1975. (See below.) Frank’s test track and field design trials were done

while Neil Armstrong was walking on the moon.  (Frank’s film is easily as

amazing as Neil’s.)

Blackmore’s mini-roundabout was never intended as a neighborhood traffic

calming circle, but instead aimed to produce a successful high-capacity

and/or offside-priority intersection within a space too small to turn

trucks. Out of respect for Mr. Blackmore’s life’s work, I suggest we give

credit where it is due, and use Frank’s  term “miniroundabout” to describe

his invention.

Ken Todd can provide historic details.

-          Todd, K.: A History of Roundabouts in the United States and

France, Transportation Quarterly Vol. 42, No. 4, Eno Foundation, Westport

CT, October 1988.

-          Todd, K: A History of Roundabouts in Britain, Transportation

Quarterly Vol. 45, No. 1. Westport CT., Eno Foundation for Transportation

Inc., January 1991.

Edmund Waddell, Planning and Research Manager

Ourston Roundabout Engineering

---

Lots of issues, questions, misunderstandings,  myths and half truths!

The UK mini-roundabout WAS any smaller form  of offside priority roundabout;

that was until 1975 when a mini-roundabout was  defined as being a  roundabout

with an overrunnable central island (wrongly) 4m  or less. Anything else with

a central island that could not be overrun and with  yield on entry was then

considered a normal roundabout. I introduced the idea of  the midi-roundabout

as being an overrunnable roundabout with a larger central  island but I was

probably not the first to use this term. A mini-roundabout is  in effect a

stand-alone truck apron and must be made as large as is necessary to ensure

deflection for all light vehicles.

We have never had all-way  stops in the UK so far as I know. The system is

very different from  mini-roundabout operation. Most of our urban and rural

intersections are  priority, i.e. a route through has priority and side roads must yield.

The reputation of mini-roundabouts has been impaired by a  number of poor installations, mostly due to poor guidance;

early schemes which  were carefully designed and applied to well-justified locations

have worked well  and had good safety benefits. It is however wrong to retrofit a mini-roundabout

 anywhere just to achieve a traffic calming effect. It is mostly such schemes  that have

failed to operate well. UK design guidance now recommends at least 500

vehicles per day on a side road before retrofitting a mini-roundabout to a

priority junction (major/minor); this is important; low levels of flow on an arm  of

a 4-arm mini will bring it into disrepute as drivers learn that there is

little ever to yield to. You will have to develop a US warrant on these matters

in particular with regard to retrofitting at 3 & 4 way stops.

 

A  mini-roundabout should be regarded as an inward extension of the normal roundabout, in particular an extension of the truck apron element which should be retained at all sizes. It is the solid centre that has to go at the point where large vehicles can no longer turn (UK ICD < 28m). The operational characteristics should be similar taking the smaller scale into account. As the site gets smaller it can be more difficult to get the deflection  particularly at  4-arm intersections. So ensure that the central island/truck apron is large enough to do this; full guidance in my publications.

 

Clive Sawers

---

Obituary from The London Times - June 14, 2008

 

Frank Blackmore: traffic engineer and inventor of the mini-roundabout

Frank Blackmore’s invention of the mini-roundabout was acclaimed for the

huge difference it made on the roads in stemming the tide of traffic jams

that has blighted motoring in Britain for more than 40 years. His innovative

measures, which also included multiple “magic roundabouts”, rendered traffic

problems considerably less acute than they might otherwise have been.

His emergence as a government traffic engineer coincided with the growing

problem of congestion on the nation’s roads that was causing road junctions

everywhere to snarl up. With no rule for giving way to traffic circulating

on a roundabout from the right, the free-for-all would often result in long

queues forming on junction approaches. As horns beeped away, overstretched

police officers would arrive on the scene, compelled to solve the conundrum

with a flurry of frantic hand signals.

Blackmore championed a growing campaign for vehicles approaching the

junction to give way at a stop line, and the rule was written into

Department for Transport guidance in 1966. The new system had an immediate

impact on reducing road accidents and improving traffic flow.

The next challenge was to design a version of the existing roundabouts that

could be applied in thousands of constricted urban settings where there was

not the space to install a conventional large roundabout.

Blackmore’s controversial solution, developed at the Government’s Road

Research Laboratory (today known as Transport Research Laboratory), was a

smaller roundabout with a 2 to 4m-wide mini-island in the middle that

minimised the curve for the vehicle driving around it, thus aiding traffic

flow. The mini-roundabout was also safer than its large counterpart because

drivers tended to approach it with greater caution.

The new roundabout, which first appeared in Peterborough in 1969,

revolutionised junction design that had up to that point been characterised

by large unwieldy roundabouts with huge traffic islands in the middle.

Blackmore developed the concept further with the painted traffic island

first used at Benfleet, Essex, in 1970. This was “over-runnable” by traffic,

making it easier for larger vehicles to manoeuvre the junction.

Despite opposition to his concept from many in an engineering profession

known for its conservatism, his roundabout designs were formally written

into government design manuals in 1975. By this time his experiments had

become increasingly radical. Among these were the “magic roundabout” in

Swindon in 1972 and multi-ring junction in Hemel Hempstead in 1973.

Such junctions comprising as many as six mini-roundabouts — like a series of

cogs in a piece of industrial machinery — did cause some chaos when first

encountered by bewildered motorists. But Blackmore proved that the

multi-roundabouts reduced speed, increased through-put and aided traffic

flow. However, the idea was perhaps one step too far for an incredulous

engineering profession, and it never really caught on. Nevertheless, his

early experiments remain as legacies to his boldness and still attract

pilgrimages from “roundabout spotters” today.

Frank Blackmore was born in 1916 in Fort National, Algeria, where his

British father, Josiah, was working as a missionary and set up an eye

hospital. An early passion for engineering emerged, encouraged by his Swiss

mother, Clarisse, who was delighted at the little devices he invented to

solve practical problems, which included a flytrap made out of matchsticks.

He left Algeria to study civil engineering in Lausanne, Switzerland, and

came to Britain in 1936 to work in the borough engineer’s department at

Colchester Borough Council.

After war broke out he joined the RAF and became a pilot of Wellingtons,

famously making an emergency landing on the beach at Ardnamurchan Point on

the west coast of Scotland and later winning a Distinguished Flying Cross.

He was closely involved in the successful testing of the Leigh Light, which

was fitted to maritime patrol aircraft enabling them to spot and attack

U-boats at night. In this work a passion for testing emerged that would

later serve him well as he turned his attention from the war effort to

fighting traffic congestion.

He rose to the rank of wing commander and remained with the RAF until 1959,

working for the Air Ministry in London and then for NATO in France and

finally as air attaché at the British Embassy in Beirut.

He left the RAF in 1959 and joined the RRL in 1960, where his interest in,

roundabouts emerged. The huge facility near Wokingham, Berkshire, was a

playground for a man who loved inventing concepts and testing them in full

scale experiments.

“He was quite unstoppable,” recalled Professor Rod Kimber, an ex-colleague

and director of science and engineering at the TRL. “He worked intensively

for hours sketching junctions that could be fitted into very small spaces.

He would keep experimenting and adjusting them until they worked.”

His iterative approach saw him make many improvements to his concept, such

as “flared approaches” of three or four lanes, that replaced traffic backing

up in single file. This design modification led to a large increase in

capacity, although to begin with drivers did not use the approach lanes

because they were so used to queuing in single file.

Blackmore was remembered among colleagues for taking his teams out onto the

road to test his ideas out. Even family holidays with his second wife Eva

and three children were not off limits to his exhaustive research, and he

would regularly stop at junctions to take photographs from every possible

vantage point while the remaining members of the Blackmore family waited

patiently in the car.

Such single-mindedness served him well as he sought to win over suspicious

traffic engineers who disliked the “shoe-horning” of junctions into confined

spaces and what they saw as excessive use of signage and road markings

warning drivers on the approach to the roundabout. As a result, some local

authorities shunned his mini-roundabouts, preferring to install traffic

lights at conventional junctions.

But many changed their minds after meeting Blackmore, who, with his mixture

of continental charm (with just the trace of a French accent) and forceful

debating technique, had a talent for changing mindsets. He was able to

persuade many local authority engineers to try things they would not

otherwise have done.

Gradually his ideas took hold, but his crowning moment came when his

mini-roundabout design was officially adopted in 1975, and recognised when

he was appointed OBE the following year. It was, nevertheless, bittersweet

for Blackmore because he did not agree with the way his designs had been

standardised in the design manuals.

Blackmore never stopped tuning his ideas, and in later years argued that the

painted island should be phased out and replaced with a slightly raised and

tapered island that would ensure that drivers curved around them and reduced

their speed to maintain safety.

Blackmore officially retired from his TRL post as scientific officer in 1980

and carried his crusade overseas as a consultant in Bangkok, Baghdad and

California. His mini-roundabout concept may receive a major application

later this year in the Nigerian capital Abuja, where power shortages often

render the signal-controlled junctions inoperable.

Blackmore was twice married, first, in 1939, to Ginon Dufour, who died of

tuberculosis in 1942. He married his second wife, Eva Johnson, in 1945. The

marriage was dissolved in 1969. He is survived by two daughters and a son of

his second marriage.

Frank Blackmore, OBE, DFC, traffic engineer, was born on February 16, 1916.

He died on June 5, 2008, aged 92

---

France's roundabout count

Have used those same Vail numbers from Guichet's presentation.  Note, a question to him after the presentation resulted in his ballpark estimate of the breakdown, 70% single lane, 25% two lane and 5% 3 or more lane.  Wonder how this might compare to Melbourne, the other location with a gross total estimate on this Listserv of 4,000-plus.

By adding another 3,000 to the Guichet figures, one comes up with about 30,000 in France this year. 

Since the US is six times the population of France conversion comes to 6,000 roundabouts a year once the US gets up to speed, and 2,000 a year in Canada which has about a third of the French population.  From a statistical and political standpoint,  comparing nations are difficult and these are ballpark comparisons--really the US and Canada could be expected to surpass the French production rates since we have all the lessons from those who have gone before as well as the triggers of energy, pollution and global warming factors as drivers.  Unfortunately, good land use practice the really important economic benefit of roundabouts--modal shift and land use benefits--still remain in the background. 

>From    : Kingsbury, Dwight[mailto:Dwight.Kingsbury@dot.state.fl.us]

 According to the table on the 2nd slide of Guichet's presentation to the 2005 Roundabout Conference ( http://www.teachamerica.com/roundabouts/RA056A_ppt_Guichet.pdf  ), there were about 26,000 roundabouts in France in 2003 and the number was growing by "more than 1000" per year (number presumably includes the miniroundabouts depicted on some slides). According to Guichet's report dated 30 Mar 2005 at http://www.setra.equipement.gouv.fr/IMG/pdf/Communication_Guichet.pdf  , "Today, they are certainly more than 27000 in France".

Dwight