Roundabouts and Older Drivers

Typical circulating speeds in Clearwater's four one-lane roundabouts such as this one are 18 to 21 kph (11 to 13 mph), and typical approach speeds (measured at the crosswalks) are 23 to 26 kph (14 to 16 mph). Photo: Ken Sides, City of Clearwater, FL.

Of the many changes that come with age, the following are particularly relevant for drivers as they negotiate intersections: narrowing of the visual field and the area of visual attention; decreased visual sensitivity to motion; a decline in the abilities to filter out less important information and continuously refocus on what is the most critical information; a decline in the abilities to perform multiple tasks simultaneously and process information from multiple sources; a disproportional increase in perception- reaction time with increase in complexity of the driving situation; and loss of the head, neck, and trunk flexibility needed to rapidly scan an intersection.

In short, older drivers need more time to perceive and evaluate situations, more time to make decisions and take action, and simpler, narrower scenes to take in—all needs that are well served by the lower traffic speeds and less complex vehicle paths of roundabouts. Events play out more slowly at roundabouts, with ample time for all intersection users to anticipate and adjust to the movements of other vehicles and pedestrians. Vehicle/vehicle conflicts and vehicle/pedestrian conflicts are reduced by about three-quarters and two-thirds, respectively, in single-lane roundabouts, and to a somewhat lesser extent in multiple -lane roundabouts.

Roundabouts are less complicated than conventional intersections controlled by stop signs or traffic signals for several reasons: Traffic threats come from only one direction. Color-coded signal bulbs and ever-cycling phases normally are not used in roundabouts. And the approaching driver need only scan straight ahead for pedestrians and about 30 degrees to the left for slow-moving approaching circulating traffic. Above all, roundabouts eliminate the need to judge gaps in fast head-on opposing traffic. Because older persons are more fragile, crash severity is especially significant. Roundabouts, intrinsically by design, limit vehicle speeds on entry and in the circulating lane. Roundabouts also separate opposing vehicle paths, thereby virtually eliminating the most serious types of crashes that occur at conventional intersections: head-on, left-turn, T-bone, and red-light running. Crashes that do occur at roundabouts tend to be either rear-end crashes or else low-angle, low-energy merging crashes with low closing speeds of 8 to 16 kilometers per hour, kph (5 to 10 miles per hour, mph). Because kinetic energy increases exponentially with velocity, roundabout crashes dissipate far less energy than those severe crash types at conventional intersections: right angles with closing speeds of 56 to 89 kph (35 to 55 mph) or head-on crashes with closing speeds of 113 to 177 kph (70 to 110 mph).

According to ongoing studies from FHWA and the National Cooperative Highway Research Program, roundabout injury crashes are reduced about 75 percent and fatalities by 90 percent or more compared with those at conventional intersections.

—Ken Sides, City of Clearwater, FL

Clearwater, FL, has the highest proportion of population aged 65 or older of any U.S. city with populations of 100,000 or more. Clearwater has built five roundabouts and has seven currently in design and five more in the pipeline, for a total of seventeen. All but the first one were proposed by—and strongly supported by —residents.

About Mini-Traffic Circles (aka Neighborhood Traffic Circles or Mini-Roundabouts)

Mini traffic circles are raised circular islands constructed in the center of residential or local street intersections. Mini cricles are a traffic calming intersection treatment employing yield control. They may also be used at uncontrolled junctions. Signs should be installed directing motorists to proceed to the right around the circle before turning right, passing through or making a left turn. Entering traffic yields to traffic in the circle and both entering and exiting vehicles should yield to pedestrians crossing the legs of the approaches to the intersection. Mini circles are commonly landscaped (often with a center tree and low-growing shrubs, flowers, or grasses). In some communities, the city may require the neighborhood to maintain the plantings. In locations where landscaping is infeasible, traffic circles can be made more aesthetically pleasing by using special paving materials.

The primary benefit to bicyclists is that, like roundabouts, mini circles slow traffic approaching the junctions by forcing motorists to maneuver counterclockwise around them. Mini circles also reduce the number of conflict points at intersections. Mini circles have been found to reduce motor vehicle crashes at the involved intersections by 90 percent or more in Seattle, WA. Mini circles may provide one of the largest safety benefits of all the traffic calming devices. Most impact studies suggest they have a nominal impact on traffic volumes, so the reduction in crashes is apparently not due to diverting traffic to other streets.

Mini circles must be properly designed with enough deflection to slow vehicles to provide safety benefits to bicyclists, pedestrians and motorists. Pedestrians with vision impairments will, however, find fewer cues to identify a gap to cross when traffic does not stop. Additionally, right-turning vehicles are not (stop) controlled at intersections with mini circles, potentially putting pedestrians at risk. Therefore, narrow curve radii should complement this treatment to discourage fast right-turn maneuvers. Adding splitter islands with pedestrian cuts to the legs of the intersection makes crossing easier for pedestrians, especially wheelchair users. Splitter islands also direct vehicles entering the intersection but require additional space.

The occasional larger vehicle going through an intersection with a traffic circle (e.g., a fire truck or moving van) can be accommodated by allowing these vehicles to make left turns in front of the circle or by creating a mountable curb in the outer portion of the circle. 

Purpose
Manage traffic at intersections where volumes do not warrant a stop sign or a signal.
Reduce crash problems at the intersection of two local streets.
Reduce vehicle speeds at the intersection.

Considerations

Consider whether bicyclists may be "squeezed" in traffic circles by overtaking motor vehicles.

This type of problem is not likely on low-volume streets, but should be considered where vehicle and bicycle volumes are higher.

Keep the turning radii low to reduce turning speeds and improve pedestrian and bicyclist safety.

Larger vehicles that need access to streets (e.g., school buses and fire engines) may need to make left turns in front of the circle, or accommodation may be made with mountable curbs on the perimeter of the circle.

Use yield, not stop, controls.

Midblock speeds may not decline, or may even rise, if intersections and mini circles are widely spaced and no midblock traffic calming measures are introduced. Traffic circles are primarily used to manage traffic flow at intersections and reduce intersection speeds, but may be combined with other measures or frequent mini circles to achieve street-long traffic calming.
Pedestrians with vision impairments will find fewer cues to identify a gap to cross when traffic does not stop  [Note: Which is another reason why Ann Arbor must change its pedestrian right-of-way ordinance to require motorists to yield to pedestrians attempting to cross the street.  Pedestrians must have right-of-way in the entire cross walk].

Chickens in New York Cross Roads At Crosswalks

New York State recently improved their pedestrian right of way law to give pedestrians right of way in the entire cross walk. Anything less than entire right of way creates an ambiguous situation for drivers and pedestrians and results in unsafe cross walks and increased pedestrian injury and death.

Watch New York State's new PSA on their new cross walk law.



New Yorks new law:

§1151. Pedestrians' right of way in crosswalks.

(a) When traffic-control signals are not in place or not in operation the driver of a vehicle shall yield the right of way, slowing down or stopping if need be to so yield, to a pedestrian crossing the roadway within a crosswalk on the roadway upon which the vehicle is traveling, except that any pedestrian crossing a roadway at a point where a pedestrian tunnel or overpass has been provided shall yield the right of way to all vehicles.

(b) No pedestrian shall suddenly leave a curb or other place of safety and walk or run into the path of a vehicle which is so close that it is impractical for the driver to yield.

(c) Whenever any vehicle is stopped at a marked crosswalk or at any unmarked crosswalk at an intersection to permit a pedestrian to cross the roadway, the driver of any other vehicle approaching from the rear shall not overtake and pass such stopped vehicle.

Watch Video of California Pedestrian Right of Way Law

California law is straight forward and clear. Drivers must yield for pedestrians attempting to enter a cross walk. Watch this video now to see how new drivers are taught about the unambiguous rules to protect pedestrians.

Mini-Traffic Circles

Mini-circles can be used on residential streets to slow vehicle speeds.

Mini-circles are raised circular islands constructed in the center of residential or minor street intersections (generally not intended for use where one or both streets are arterial streets). They reduce vehicle speeds by forcing motorists to maneuver around them. Mini-circles have been found to reduce motor vehicle crashes by an average of 90 percent in Seattle, WA (Seattle has over 700 mini-circles). Drivers making left turns are directed to go on the far side of the circle prior to making the turn. Signs should be installed directing motorists to proceed around the right side of the circle before passing through or making a left turn. Mini-circles are commonly landscaped (bushes, flowers, or grass), most often at locations where the neighborhood has agreed to maintain the plants. In locations where landscaping is not feasible, traffic circles can be enhanced through specific pavement materials.

Mini-circles are an intersection improvement as well as a traffic-calming device and can take the place of stop or yield signs. Many unwarranted four-way stop signs are installed because of the demand for action by the community.

Mini-circles must be properly designed to slow vehicles and benefit pedestrians and bicyclists. Right-turning vehicles are not controlled at an intersection with a mini-circle, potentially putting pedestrians and bicyclists at risk if not designed correctly.

Therefore, tight curb radii should complement this treatment to discourage high-speed right-turn maneuvers. The occasional larger vehicle going through an intersection with a traffic circle (e.g., a fire truck or moving van) can be accommodated by creating a mountable curb in the outer portion of the circle.
Purpose

* Manage traffic at intersections where volumes do not warrant a stop sign or a signal
* Reduce crash problems at the intersection of two local streets
* Reduce vehicle speeds at the intersection

Considerations

* Do not make generous allowances for motor vehicles by increasing the turning radii—this compromises pedestrian and bicyclist safety.
* Larger vehicles that need access to streets (e.g., school buses and fire engines) may need to make left-hand turns in front of the circle.
* Other traffic control is often not needed; however, if needed, use yield, not stop signs.
* Mini-circle landscaping should not impede the sight distance.
* Treat a series of intersections along a local street as part of a neighborhood traffic improvement program.

Estimated cost

The cost is approximately $6,000 for a landscaped traffic mini-circle on an asphalt street and about $8,000 to $12,000 for a landscaped mini-circle on a concrete street.