This page is intended to help educate the reader about the use of traffic circles and modern roundabouts . Please send feedback on usefulness, questions and comments to daniweber@daniweber.com.
Traffic circles are different from roundabouts in that they are intended to slow traffic as well as reduce collisions by reducing possible conflicts. Roundabouts are placed where the intent is to improve traffic flow . In the central neighborhood, we are concerned about speeding and cut-through traffic, so our intent is to reduce this by installing traffic circles that will slow traffic as well as make the area safer for children to play. Thus, our existing traffic circle and new planned ones have 4- way stops in addition to the circle.
The specific traffic circle we are trying to make permanent is located at 5th Ave. and Eldorado St. in San Mateo. This is a temporary traffic circle intended to stop cut-through traffic and slow speeds installed at the request of the Central Neighborhood Association.
The San Mateo Public Works Commission held a public hearing on the status of this traffic circle in September of 2001 and voted to continue the temporary status for 6 more months and hold another hearing at that time. It is critical that the neighbors who want this circle to be made permanent voice their support. The Commissioners want to support this circle over the objection of the Public Works department, but they can only do this if they receive significant support from the neighborhood.
The commissioners comments were:
1) That they recognized the need for some traffic calming measures on Fifth Ave. and they mostly supported the traffic circle. They felt it was possible it should be modified to improve its effect and wished to study this in more detail.
2)The commissioners were also concerned about the mixed reaction from the community and want to see clear support for this traffic circle at the next hearing if this is to be made permanent.
What you can do:
Educate yourself by reading this page and following these links.
Write a letter to the San Mateo Public Works Commissioners in support of this
traffic circle and cc the letter to Laurie Watanuki (lwatanuki@earthlink.net),
head of the Central Neighborhood Association
Attend upcoming neighborhood meetings for education and networking
Tell your neighbor
Contact us to be put on the volunteer list
Attend the San Mateo Public Works Commission hearing tentatively set for March,
2002
Examples
Our traffic circle at 5th and Eldorado
Mini roundabout similar to ours but with splitters & without stop signs
Benefits of Traffic Circles and Roundabouts in General:
50-90% decrease in crashes and greatly reduced severity of crashes which do occur.
The reasons include:
Reduction in possible level of conflicts. At a four-way intersection there are 32 possible conflict points between vehicles and only eight at roundabouts. Pedestrians face six conflicts when crossing only one leg of the road whereas at a roundabout they only have two.
diagrams from http://www.roundabouts.net/newpage3.htm
Speeds are reduced due to the circle and collisions are offset, so it is easier to stop or the resulting force of impact is greatly reduced. Speeds are controlled at 15 mph through the intersection.
Crashes at signalized intersections are frequently high-speed right angle and left turn crashes whereas crashes at roundabouts are primarily rear end or low speed merge crashes.
Increase safety for pedestrians if properly designed by creating a refuge and moving the crosswalk away from the actual intersection.
Bicycles can merge safely with car traffic and travel at the same speed as cars, thus reducing possible conflicts.
Traffic circles are less costly to build and maintain than a signalized intersection, provide opportunity for landscaping and create a presence and define an entrance to the neighborhood.
The design guidelines at
http://www.tfhrc.gov/safety/00-0676.pdf
describe improvements to make to this traffic circle to reduce chances of illegal left turns and improve pedestrian safety.
The traffic circle works well as it is, with zero collisions since it was installed. However, possible conflicts exist which can be diminished.
The circle could use island splitters as shown in the left picture, courtesy
of http://www.Trafficcalming.org
Technically this shows a roundabout and not a traditional traffic circle. which is above and right, however, even traffic circles can have splitters, as shown in this photo, also from the same website:
Note the bicycle taking the lane. The splitters can be made of raised concrete to force the cars right.
Below is a sample letter to send to the commissioners: Feel free to copy and paste. Try to individualize if you can. You can also simply send a letter stating "I suppport this traffic circle and I live at such and such address"
date
San Mateo Public Works Commission
330 W. 20th Ave. San Mateo, CA
Jay Finkelstein
Robert Logan
Kelly D. Moran
Chris Schulz
Marion Weiler
RE: Traffic Circle at Fifth and Eldorado:SUPPORT
Dear Commissioners,
As a local resident who traverses this intersection daily, I strongly support making this traffic circle permanent.. Studies have shown that modern roundabouts can cut serious traffic collisions by 90%.
We would recommend several additions to the design. However, even without the improvements that would make this traffic circle a modern one, it appears to have remarkably cut traffic speeding and made this intersection much safer to cross.
One: Place center triangular splitters in the front of each side of the traffic circle to keep cars from cutting the wrong way.
Two: The sidewalks should be set further back from the intersection so pedestrians are not threatened by cars entering the crosswalks as they negotiate the curves.
Three: Signs stating "bikes merge with traffic" as is seen on a narrowed section of Sand Hill Road in Menlo Park should be placed in front of the approach to each side of the traffic circle(s). Bicyclists need to take the lane in order to negotiate the traffic circle without being in danger of being cut off or sideswiped, and are allowed to do so under CVC 21202. In order to do so, they need to be in the lane on the approach. Motorists do not necessarily know this or understand the reasons why. Some cyclists may try to hug the outside edge, thus setting up a potential conflict. A sign can help to reduce the chances of these possible conflicts arising.
These changes should fix any small problem that exists due to the circle. Again, the benefit of traffic circles greatly outweighs any drawbacks. I am extraordinarily grateful and pleased about the traffic circle being in my neighborhood and hope to see many more. They are wonderful traffic-calming devices and provide an excellent opportunity to beautify the road. Please make this traffic circle permanent.
Sincerely,
name
address
Also, here are urls for research:
http://www.tfhrc.gov/
http://www.tfhrc.gov/safety/pedbike/pubs/99035.pdf
http://www.tfhrc.gov/safety/00-0676.pdf
http://www.tfhrc.gov/safety/00068.htm
http://www.tfhrc.gov/pubrds/fall95/p95a41.htm
http://www.hwysafety.org/
http://www.hwysafety.org/srpdfs/sr3505.pdf
http://www.hwysafety.org/srpdfs/sr3403.pdf
http://www4.nationalacademies.org/trb/onlinepubs.nsf/web/NCHRPSynthWeb
http://roundabout.kittelson.com/
http://roundabouts.kittelson.com/dbase/queries/inv.cgi
http://www.roundabouts.com/edu.html#anchor739421
http://www.roundabouts.net/
http://www.roundabouts.net/newpage3.htm
http://www.roundaboutsusa.com/
http://www.roundaboutsusa.com/design.html
http://www.ksu.edu/roundabouts/
http://www.ksu.edu/roundabouts/sr3607.pdf
http://www.ksu.edu/roundabouts/videos.htm
http://www.ksu.edu/roundabouts/upstruck.mpg
http://www.milpasroundabout.com/index.html
http://www.milpasroundabout.com/automobile.html
http://members.aol.com/penntraff/mini-roundabout/
http://members.aol.com/penntraff/mini-roundabout/largerbt.html
http://www.trafficcalming.org/ROUNDABOUTS.html
http://www.dlzcorp.com/seg/modern.html
http://home.planet.nl/~jvansant/veld.htm