Barry Crown is a renowned roundabout expert from the United Kingdom who has designed I believe hundreds of roundabouts in his career, including several in the United States. Barry has put together a response to the Wall Street Journal article that I think Motasem and many other traffic engineers should read. The text of his response is included below:

ROUNDABOUTS IN THE UNITED STATES

The article in the Wall Street Journal painted a black picture about roundabout safety and their suitability for the United States. The Clearwater Roundabout was cited. This response fills in the gaps in the article and redresses the balance.

The design of the Clearwater Roundabout was uncommonly complex. It converted 5 intersections into one intersection that had to accommodate Spring Break traffic volumes of 50,000 vehicles and 6,000 pedestrians per day. The aims of the Landscape Architects and the Fountain Designers also contributed to the design complexity. The design sought to find the best balance between these unavoidably conflicting aims.

The roundabout has had a large number of vehicle crashes at the exit onto the Causeway and at the exit into Coronado Drive. However, there have been no pedestrian accidents at the roundabout. This clearly reveals that the best balance was not initially achieved.

In July 2001, my recommended revisions to signing, striping, and lane arrows were introduced at the Causeway exit. The crashes subsequently dropped from an average of 25 to 0 crashes per month. There have been no crashes at this location since that time.

This clearly demonstrates that the fault was with design detail and not the drivers.

To resolve the crash problem at the Coronado Drive exit the curbs need to be realigned. This work will be completed by the end of February 2002 when a dramatic reduction in crashes is expected. (Similar to the reduction at the Causeway Exit.)

Over the past twelve years about 300 hundred modern roundabouts have been constructed in the United States. Almost all have been unqualified successes. A study commissioned by the Insurance Institute for Highway Safety determined that roundabouts in the United States have reduced all crash types by 40% and injury crashes by 80%, at sites where they replaced other types of intersection. We do not know of any other type of highway
improvement that has such a high success rate.

Considering that the US Engineers are relatively new and inexperienced at roundabout design it is to their credit that their failure rate is only a few percent. This is exemplified by US public opinion, that is typically about 80-90% against building a roundabout, but after construction this soon changes to about 80-90% in favor.

The lesson to be learnt is not that roundabouts a bad for the US, but that design faults lead to failure while good design produces roundabouts that are safer than any other type of at-grade intersection in the United States.

R.B. Crown
28th January 2002

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