[BikeLongmont] more about traffic circles and bicyclists

[Richard Masoner]

  Traffic circles and mini-roundabouts are being installed in
Longmont. There are a couple on Deerwood south of 9th, some on Olympia
west of Pace, one at Collyer & Longs Peak, and a couple are being
installed on Mountain View Avenue (but I forget where).

  Len Marques asked me to comment on the traffic circles so I've been
doing some research about them. Here's what I've discovered:

  * While there are significant, proven safety benefits for motor
vehicles and pedestrians, research in the UK and France shows that
bicyclists have about three times the risk for accidents, serious
injuries, and death at roundabouts than in signalized intersections.
NOTE that these studies are for roundabouts rather than the small
traffic circles in Longmont. I also don't know about traffic volume or
speed, whether these accidents occur in double-lane roundabouts, and
whether the bicyclist is doing something preventable to increase the
risk of accidents (e.g. riding along the outside edge of the circle
rather than with the other traffic).

  * Most bicyclist advocacy organizations in the United States are
opposed to traffic circles because of the safety issue. Some recognize
the other safety benefits and accept traffic circles.

  * The US DOT FHA has a document "Roundabouts: An Informational
Guide."  This is not a standard or anything, just something to
document what other countries and some states are doing along with
commentary about the current state of the art. Some specific
recommendations they make with regard to bicyclist use include:

   -- Bike lanes must stop well ahead of circle entry to encourage
bicyclists to mix with other traffic. Something to consider might be
signage to educate motorists and bicyclists that through and
left-turning bicyclists should "take the lane" in low-speed traffic
circles. Bicyclists making an immediate right turn may safely ride
along the outside edge of the circle.

   -- A ramp-up from a bike lane to the sidewalk should be provided at
circle entries for those bicyclists who wish to traverse the circle
pedestrian-style on the sidewalk and crosswalks. Similarly, a
ramp-down from sidewalk to bike path is provided at circle exits.
(PLEASE don't make these ramps like the tiny 30" things we have on
Missouri Avenue from the Lefthand Creek sidepath with the right-angle
entries). Chapter Six of the Informational guide gives specifics on
what these ramps should look like.

  -- Bike lanes within circles are Very Bad News.

  -- At high volume, high speed intersections, alternate routes for
bicyclists should be considered. I don't think we're considering
installing traffic circles on streets like this in Longmont.

  If you're interested in the issue, the FHA Informational Guide seems
to be the right resource. It's available as several PDF documents at:

   http://www.tfhrc.gov/safety/00068.htm

  Much more information about roundabouts is at:

    http://roundabout.kittelson.com/index.html

  I appreciate the city in working with us to guage acceptance and
usability of these traffic calming devices.

Richard Masoner