Traffic Management and Roundabouts

Traffic Management and Roundabouts

The following position statement was approved at the July, 2002 meeting of the Santa Barbara County Taxpayer Association meeting, and has never lost its validity. Another Timeless Assessment.


Questions or comments should be directed to Mr. Joe Armendariz, Director.


The Chair of the Transportation Committee at time of approval was Scott Wenz.



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Approved and adopted at the July 2002 meeting
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With the increased population density witnessed in the entire County of Santa Barbara, and the concurrent increases in cars and trucks on the roads it is obvious that roundabouts or "rotaries"are not desirable intersection design for intra-city urban locations. Vehicle safety, evacuation route concerns, cost, increased size of intersections, loss of parking, creation of un-regulated intersections, and the need for safe bicycle/pedestrian alternatives that roundabouts adversely impact are all points against their construction.
Roundabouts are reasonable alternatives for highway and freeway junctions. Where there is enough room to create the proper deflection angles, maintain vehicle speed, and have safe travel because of the available land for proper planning they make sense. End of conclusion


A significant portion of the "Alternative Transportation" discussion in Santa Barbara County is the management of intersections. One of the most persistent designs put forth by anti-car groups is the Roundabout. When confronted with the charge that this is a "traffic calming" device intended to cause congestion and inhibit the smooth flow of traffic they have consistently denied this. Yet the Federal Department of Transportation is circulating an independent publication called, Designing Sidewalks and Trails for Access3 where the roundabouts are listed under "traffic calming" devices.2 This publication quotes The Institute of Transportation Engineers as stating that traffic calming is "...the combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior, and improve conditions for nonmotorized street users, 1999."
Examples of roundabouts often promoted are those primarily in Europe and England. The chief argument for roundabouts is that they provide a continuous feeding of traffic through an intersection without the need for stopping. The theory then states that as a result of this continuous movement of traffic there is reduced travel time, reduced pollution, and reduced accidents (and severity of accidents). Most often the primary argument "for" is based solely on perceived time delays. The most significant analysis of intersection design currently used is based upon delay. This is qualified in a system based upon the so called Level Of Service (LOS). The grading of each intersection, "A" through "F" is based on the ability to process traffic with or without significant delay.
The argument against roundabouts include the lack of pedestrian safety, lack of bicycle safety, placement requires more land area then conventional intersections, a greater cost of construction, the need to remove parking adjacent to roundabouts, and the fact that as an un-regulated intersection accident responsibility is difficult to assign. This difficulty exists because vehicles are not required to stop. Right of way determination is at best difficult to determine. Accident rates often increase after installation of a roundabout.


Location Examples

In the United States, Massachusetts stands out as having the greatest number, and the longest history of roundabout application. The traffic review group Cars Are BasicTM contacted the head of traffic management for the state of Massachusetts (1998) and asked him as to his experience and opinion of roundabouts. He pointed out that his state was in the process of removing small and medium roundabouts (rotaries) because of the problems of congestion that they cause. He stated that when volumes of traffic reached rush hour peaks, and with the added problem of pedestrian management, they are not desirable. The direct quote is, "roundabouts are contraindicated where pedestrians are present." He did state that he supported roundabouts on large highway and freeway interchanges as long as they are designed in accordance with specific safety standards and include properly designed entry point deflections. The proper entry angle is dependent on having ample land available with adequate site lines on each approach, and a large turn radii. He supports the concept and use of roundabouts in proper context. This is the difference between the old concept of traffic circles or "rotaries" and the modern day roundabout.


Park City Utah is another location that has been held up as a great example of roundabout installation. Talking with both commuter workers and residents of Park City the apparent reality is that the construction has created more problems then it solved. The problems are associated with peak traffic congestion (roundabouts are supposed to solve this), and the creation of an un-regulated intersection. All of these problems are the issues that have plagued the City of Santa Barbara.


Santa Barbara
There has been a consistent public relations campaign supported by those interested in making car travel a thing of the past. The Santa Barbara News-Press last year printed an article praising roundabouts with a picture of the Milpas/Carpinteria Street roundabout at a low traffic period. This story was a syndicated publication that based its information on a report published in the American Journal of Public Health, April 2001, Vol. 91, No. 4. Reading the abstract one would believe that roundabouts are akin to the second coming of the savior of the world. A critical review of this is attached at the end of this paper. This paper pointed out that the "expected" number of accidents at this intersection without conversion to a roundabout equaled the actual accidents after conversion to a roundabout.2
The short of it is that the methodology of the paper is flawed, yet to their credit the authors point out that the type of small and medium roundabouts of the type planned in this county are on streets that should not have them. These are streets that are business oriented, tend to have pedestrian traffic, have periods of high traffic flow as diversion routes, and/or have substantial bicycle traffic.
Salinas/APS - Milpas/Carpinteria
A quick look at the reality of both the Salinas St./APS/Sycamore Canyon roundabout (rush hour and diversion route), and the Milpas St./Carpinteria St. roundabout (business & rush hour) proves the wisdom of the Chief Traffic Engineer of the State of Massachusetts. When the City of Santa Barbara traffic engineer, George Gerth claimed "success" of the roundabout at the Salinas intersection as an example of why the Milpas roundabout would work it would appear that he did not look at the results of the predicted theory of recognized roundabout experts. This same traffic manager has declared the Milpas St. roundabout a success despite official City of Santa Barbara accident figures to the contrary (300% increase in traffic accidents, 2 deaths, and congestion at rush hour at Milpas/Carpinteria Streets.)4. It is note worthy here to mention that approximately 1/3 of the increase in accidents reported are due to intoxication. Which means that those with impairment have difficulty negotiating this type of intersection. There is anecdotal evidence from witnesses and debris that more than the reported accidents have occurred. The current protocol for investigating automobile collisions is that no reports are made unless there are injuries or at least one vehicle was damaged so badly it was un-driveable and had to be towed from the scene. Additionally the following effects occurred: it was 100% over budget (2.5 vs. 5.1 million dollars), several months over due on completion, dramatically hurt nearby local businesses, and has yet to have built the required pedestrian bypass that will cost millions of dollars more.
An "Unintended Result" of the Milpas/Carpinteria roundabout is the fact that the amount of traffic Eastbound on Carpinteria St. exceeded design year (2015) projections within a year of the installation. Vehicles are not required to stop, entrance to the street from the roundabout is at an accelerated rate, and it encourages north bound drivers to turn eastbound on Carpinteria without slowing. The change to a roundabout eliminated the safety factor of a regulated intersection. The accident and death rate further down the block on this street sky rocketed after the roundabout was built and residents demanded the city do something about the speed and traffic volume on the street. All this as a direct result of a design that was intended to make traffic safer.


Six roundabouts have been proposed for the new City of Goleta. These proposals are in part based upon glowing reports of the "success" of the Salinas and Milpas street roundabouts by obviously biased proponents. In addition to the dangers inherent in a roundabout sited at an inappropriate location similar to the Milpas St. roundabout is the increased expense verses a standard intersection, and larger land area needed for building such a device. This is further supported by the example of the Salinas/APS rotary.
Just the "improvements" after construction like the circular median cost an additional $250,000.00, for an area approximately 20 ft. across and has not provided any remedy for pedestrians. Recently the city tore out this and planted a tree in the middle of this circle despite the fact that it was designed to be driven over in case of emergency. How the City of Goleta will handle such pressures will be instructive.


North County
It would appear that North County (Lompoc, Santa Maria, Guadalupe) is under these same pressures to "calm" traffic. Yet these are locations that are growing and developing traffic counts and increased populations that the above examples dictate should not have roundabouts. The only instances that would appear to benefit by the construction would be some of the intersecting highways and freeways. There is land space available to build the multi-acre roundabouts that work efficiently, do not have the inherent problems of pedestrian traffic, tight radii, insufficient lanes, and business traffic. A concern that this report has is the City of Santa Maria that constructed a roundabout at a growth area. This has the potential of becoming the same type of congestion and accident problems that have been reported above.
Impacts on pedestrian access
Under signals Building a True Community (final report) has developed among its guidelines for for roundabouts the recommendation that "(C) Signals. A pedestrian acutated traffic signal complying with x02.5.2 shall be provided for each segment of the crosswalk, including at the splitter island. Signals shall clearly identify which crosswalk segment the signal serves."1 This completely negates the concept of free flow of traffic that the proponents of roundabouts have tauted to be a primary reason for building roundabouts. The discussion section of this chapter is quite detailed but it is instructive to quote the following: "While this traffic pattern has been an asset to traffic planners in controlling and slowing the flow of traffic at intersections in lieu of having a signalized intersection, the absence of stopped traffic presents a major problem for blind and visually impaired pedestrians when crossing. .... Pedestrians report that vehicles at roundabouts, right slip lanes, and other unsignalized pedestrian crosswalks often do not yield for pedestrians."1 What this states is that most certainly roundabouts are not pedestrain friendly and they are most definitely considered traffic calming devices despite the ascertations of the city of Santa Barbara to the contrary.
The following are quotations from Desiging Sidewalks and Trails for



Negative impacts:
Motorists exiting the roundabout are often not required to yield to pedestrians..;
If properly designed, the crosswalk locations are set back from the intersection,.... Setback crosswalks are difficult for people with vision imparments to identify becasue they are not at the roundabout itself. (note this takes additional space that detracts from parking capability of the street);
Busy roundabouts provide very few gaps long enough to cross. This can be especially problematic and unsafe for pedestrians such as children, elderly with mobility and cognitive ivsion impairments;
Pedestrians with vision impairments experience difficulty seizing the right-of-way from exiting drivers due to the lack of pedestrian to driver eye contact;

Due to the wide turning radii at the corner, pedestrians with vision impairments may fail to identify the intersection; (note this includes intoxicated walkers)
Roundabouts are confusing for people with cognitive impairments due to the irregular design of the intersection....; and
When a crosswalk is setback from the intersection, pedestrians have to walk longer distances out of their way to cross the street. Some pedestrians will use the most direct route regardless of the crosswalk. (note this phenomina has been observed by members of this committee at the Milpas/Carpinteria roundabout from the first day of operation)

Add these negative observations to problems listed above and the grave concerns about emergency evacutation then the problems become daunting. The admonition to not build roundabouts (rotaries) where there is heavy peak traffic conditions, constantly heavy traffic conditions, commercial traffic conditions, or concerns about bike and pedestrian takes on important and serious weight in this light.
Final note

It appears that a common tactic by those in favor of roundabouts is to dismiss the expense and other objectionable factors related to them. They then pick an intersection that is in need of long over due maintenance, and possibly has other factors contributing to hazardous traffic operation such as improper signalization. Multiple options are then presented all of which include a variation of what they want and leave out other reasonable alternatives. This was very apparent with the City of Santa Barbara decision to build the Milpas/Carpinteria Roundabout.


With the increased population density witnessed in the entire County of Santa Barbara, and the concurrent increases in cars and trucks on the roads it is obvious that roundabouts or "rotaries"are not desirable intersection design for intra-city urban locations. Vehicle safety, evacuation route concerns, cost, increased size of intersections, loss of parking, creation of un-regulated intersections, and the need for safe bicycle/pedestrian alternatives that roundabouts adversely impact are all points against their construction.
Roundabouts are reasonable alternatives for highway and freeway junctions. Where there is enough room to create the proper deflection angles, maintain vehicle speed, and have safe travel because of the available land for proper planning they make sense.


1. Building a True Community
Final Report - Public Rights-of-Way Access Advisory Committe
U.S. Architectural & Transportation Barriers Compliance Board
January 10, 2001

2. Crash and Injury Reduction Following Installation of Roundabouts in the United States.
R.A. Rerring, B. N. Persaud, P. E. Garder, and D. Lord
American Journal of Public Health
April 2001, Vol 91, No. 4

3. Designing Sidewalks and Trails for Access
Best Practices Design Guide
U.S. Department of Transportation
Federal Highway Administration
September 2001

4. Milpas Roundabout Traffic Study
Presented July, 2 2001
Willdan Associates
City of Santa Barbara, California


Bibliography item #2The following review of this article was prepared by a former City of Santa Barbara police officer who worked as a traffic accident investigator and is presently working locally as an attorney.

A. Methodology

1. The method of extrapolation using a small sample is bad science. The projections of how many accidents the researchers predicted "would have occurred" if the roundabouts were not installed is not supported by an empirical evidence.

2. Only 4 intersections involving signal lights were studied before and after the conversion to roundabout.

3.. Any bona fide reduction in accidents or more accurately injury accidents are a result of the forced reduction in speed not the roundabout per se. The theory states that the angle of deflection is such as to force a speed reduction lessening the severity of impacts.
a. No significant information is provided as to whether the signalized or previously un-controlled or partially controlled intersections had speed limits of 35-55 mph. Obviously a reduction of such speed by any means at any intersection will reduce accident severity and frequency.

4. There is no evidence that fewer accidents are occurring. There is in fact only evidence that there may have been a reduction in REPORTED accidents in some intersections. The reduction if any, in reported accidents, is as likely a result of the reduction of severity of accidents (not supported), and the vehicles are driveable with no report made. No law enforcement agency is called or the drivers would not wait for a responding agency.

B. Specifics
1. As the reader can see there was a 40% increase in accidents in the Salinas/APS roundabout which was included in this national study.

2. 11 "property" and no "injury" accidents prior to the roundabout to an increase of 17 total accidents including 2 injury after conversion to roundabout. The authors describe the Salinas/Sycamore Canyon/APS roundabout installation as a failure. This admitted failure is said to be because prior to conversion to a roundabout all five entry points were controlled by stop signs (all way stop). This stop sign controlled design is concluded to be as safe or safer than the roundabout configuration.
C. Relation to Milpas

1. The Milpas roundabout was too new to be included but as you know our experience confirmed by the City of Santa Barbara Police Department accidents statistics, it is very likely that safety is not improved by roundabout conversion except in rural, low volume and often higher speed uncontrolled or partially controlled intersections.


D. Conclusions
1. The authors admit roundabouts are not particularly safe or efficient for busy high volume urban intersections, particularly when used also by bicycles, pedestrians and mixed types of vehicles such as trucks and buses.

2. The authors admit that roundabouts may not be as safe as conventional intersections for pedestrians and bicyclists. The context or location of any roundabout as well as its design, are critical to the determination of whether or not to install a roundabout.

3. The attempts to estimate or predict the likely reduction in accidents that would or could result from roundabout conversion is a virtual impossibility because of elements of chance and changes in volume and traffic patterns brought about by the roundabout (and demographic changes of population).

4. Traffic volume and relative speeds are more important factors in the likelihood of accidents than any other element(s). e.g. The pre roundabout traffic accident "patterns" were non-existent 1995 - 1, 1996 - 6, 1998 - 0, etc. There are many intersections which have gone years with no accidents reported then suffered a spate of 3-4 accidents in one year. Often these are pure coincidence, other times the result from changing temporary physical conditions , overgrowth, visual obstruction, or weather conditions and the volume of vehicles using that intersection during that period or season.

5. The paramount problem with the current intersection analysis is that it is pre-occupied with time delays. The level of service (LOS) approach grades intersections on an A through F scale based entirely on delay. i.e. whether queues develop, and at signalized intersections whether all waiting vehicles "clear" the intersection in one or more signal cycles, and how many seconds they must wait. This approach fails to consider safety, comfort and convenience factors, non-reported accidents, new accidents, fear and road rage incidents.

6. In addition the Americans with Disabilities Act (ADA) provides that no government may alter or modify any existing public facility so that it results in a condition less safe or convenient for those with a disability. Signalized intersections like the Milpas/101 intersection provided protected intersections right of way for pedestrians using "walk", "Don't Walk" lights. To remove these protections for a system that leaves a pedestrian to fend for themselves (that is cross only when they think it is safe to do so) is a violation of the A.D.A.
The proponents of roundabouts often know little about any of these factors.