Traffic Signals Could Seriously Harm Congestion and Safety

at Chevy Chase Circle

By Mary E. Rowse

September 2004



Traffic safety and congestion at Chevy Chase Circle could dramatically worsen if District Division of Transportation (DDOT) officials proceed with their ill-thought-out plan to install traffic signals inside the Circle at both Western Avenue entrances.

DDOT's justification for these signals is that the Chevy Chase Advisory Neighborhood Commission (ANC) asked for them to control congestion and improve pedestrian access to the center island. But ANC Commissioners are not traffic engineers and until DDOT makes it a priority to stop vehicles from crashing through and damaging the fountain, benches and trees inside the Circle, it would be irresponsible to encourage citizen access to this area. Furthermore, DDOT has performed no studies to determine if congestion at the Circle will improve with signals. In fact, the opposite could easily occur because this circle conservatively handles anywhere from 50-80,000 vehicles per day.

It is astounding to note that when the Mayor first announced in May 2001 that signals were going in, DDOT officials had not performed one single traffic study on the Circle. The one study that had been done in 1988, was lost. To date, DDOT has still not performed the usual studies other neighboring jurisdictions automatically undertake before determining whether signals are justified in an area, such as a traffic safety analysis of accidents and their causes, a "Time Delay" study to determine if signals would improve or worsen delays motorists already experience at the Circle, or computer modeling to determine the impact signals will have on congestion and safety for drivers and pedestrians in the area.

The only study DDOT has done, was a hastily compiled one in January 2002, nine months after the Mayor's announcement. It relies heavily upon 1993 traffic count data from neighboring streets and intermixes it with just four hours of 2002 traffic counts from Western Avenue only! No other streets were reviewed. In addition, the study inappropriately applies rules for signalizing four-way intersections to signalizing a circle, and it reports only three accidents at the circle in a three-year period. The study doesn't examine the causes of these accidents nor does it appear to have contacted other jurisdictions (aside from DC police) such as Montgomery County and the U.S. Park Police for their accident reports. (All three jurisdictions respond to accidents at the Circle, depending upon where they occur.)

Circles, first introduced in the U.S. in 1905, were never meant to be signalized. Their purpose was to bring thousands of vehicles on interconnecting roads safely and efficiently through a single point. Not only do traffic engineers rarely advise signalizing circles, they also rarely advise signalizing four-way intersections (unless justified) because signals can greatly decrease safety for both drivers and pedestrians. It's a fact that there are more fatalities at signaled intersections in this country than at non-signaled ones. And because signals are extremely expensive ($150,000 +) and usually do not offer the exact solution needed for an area, traffic engineers use them only as a last resort, after all other traffic measures have been tried.

In a meeting last month, traffic engineers from the Maryland State Highway and the Federal Highway Administrations warned DDOT officials that signals at Chevy Chase Circle were premature and might do more harm than good unless the city first tried improving lane markings, signage, lighting and the geometric design of the circle's outer perimeter. Signalizing the Circle could create a situation where rear-end accidents and other fender-benders dramatically increase because drivers have limited vision of an unexpected signal and will be braking on a curve. Vehicles that once changed lanes with ease in a free-flowing situation, would be required to change lanes from a stationary position, drastically affecting the safety and flow of Circle traffic.

Traffic signals will not stop aggressive drivers who fail to yield to traffic inside the Circle, who prematurely enter the circle trying to get ahead of a car already inside, who cause broadside collisions inside the Circle when they prematurely enter in front of oncoming traffic, or who crash through the center island (particularly at night or in poor weather) because they didn't know the Circle was there. Solving these problems involves creating better signage, lane markings, new lighting inside the Circle at night (including the fountain), developing channelized "splitter islands" on Western Avenue to direct traffic away from the center island and into the circle, and perhaps re-timing existing signals (such as the one at Connecticut and Oliver) for southbound Connecticut Avenue traffic only, in order to reduce congestion inside the Circle and prevent traffic backups on Western Avenue.

Anyone who has ever driven around Chevy Chase Circle has to admit that while there are problems, most of the time traffic flows fairly smoothly inside. Instead of proposing an ill-thought out plan for signals, DDOT officials should carefully analyze the problems that do exist there and develop solutions that not only specifically address traffic and safety concerns, but that also respect the Circle's original purpose and protect it as one of the most beautiful and historic gateways into Washington.


Why Accidents Occur at Chevy Chase Circle

and Why Signals Are Not the Answer

By Mary E. Rowse

Updated July 28, 2009

Land Mass inside the Circle (“the Island”) is dark at night and difficult to see for those unfamiliar with the area. Drivers don’t know the Circle is coming up especially on Western Avenue and on Connecticut Avenue, northern approach. All signs must be retroreflective.

There are twelve streetlights that dot the circumference of the Circle. Many are not consistently working and their light creates too great a contrast for drivers who find it more difficult than ever to notice the land mass of the Circle.

As a result, vehicles have driven into the center of the Circle and severely damaged the landscaping, benches, and fountain because they didn’t know the Circle was coming up and couldn’t see it at night until they were upon it.

Possible Solutions:

* Artfully light the inside of the Circle to illuminate the land mass, trees and fountain at night. These lights would be installed where vehicles could not damage them. Lights can be strategically placed in trees and on the ground so as not to shine in the eyes of drivers. (The overhead streetlights already do that) Goal is to artfully illuminate the trees and land mass that drivers must avoid when traveling around the Circle.

* Create a more even lighting area at night around the Circle so that there is no sharp contrast between the very bright, intrusive light cast by the 12 streetlights around the Circle and the very dark land mass inside. Lighting the circle inside will help do this.

* Install reflectors on the side of trees facing the Circle and/or on foot-high brown wooden posts around inside circumference of Circle (examples can be found on Rock Creek Parkway).

* Install reflectors/reflective markers around the base of the curb around the outer circumference of the Circle.

* Install reflectors (raised pavement markers) into the lane markings near the end of all four Connecticut & Western Avenue approaches and also around the Circle dividing the lanes. The smaller streets like DC’s Chevy Chase Parkway and Maryland’s Magnolia Parkway and Grafton Street don’t need this.

* Install effective signs warning that a Traffic Circle is ahead on four major approaches. The current lighted sign facing southbound traffic in Maryland is okay and is certainly better than nothing!

Problem No. 2

Vehicles approaching Chevy Chase Circle aren’t aware they’re coming to a Circle. Drivers must be made aware that a Circle is ahead.

* Install clearer retroreflective signs that indicate a circle is ahead. The existing green & white ones do not clearly indicate this. The pictorial ones with four spokes through them are ok, but not great.

* Raise the white painted triangular islands currently chanelling traffic on and off Western to sidewalk height—create splitter islands. Pave them so pedestrians can seek refuge on them. Place a blinking light post to alert traffic of impending circle just as there is one facing northbound traffic leaving DC and going into the Circle at Oliver Street, NW.

* Install reflectors that follow the curve of these splitter islands to guide drivers. (One of the most important indicators to drivers heading southbound on Connecticut Avenue into the District that things are changing, is the neon yellow/green pedestrian sign and the arrow sign that greets them as they are about to merge onto the Circle from Maryland.)

* Install blinking yellow or red lights on Western and Connecticut Avenue approaches with a sign that says “Circle” or “Circle Ahead

* Install rumble strips on both Western & Connecticut Avenue approaches to warn drivers that changes are ahead—similar to what drivers encounter approaching toll booths..

Problem No. 3

Traffic entering the Circle often fails to yield to traffic already inside.

Solutions

* Install electric blinking signs that say “Yield to Traffic in Circle”

* Paint “Yield” or “Yield Ahead” in white inside the lanes to warn drivers.

* Ticket aggressive drivers who fail to yield

Make sure traffic lanes are marked with arrows or dotted lines so traffic in inner lane, for example, knows it can’t cross to the far left lane. RPMs in lane dividers

Problem No. 4

Pedestrians find it difficult to access the Circle

Before pedestrians are given greater access to the Circle, safety measures must be put into place that will prevent vehicles from crashing through the Circle and killing them. It is not advisable to create greater access to the Circle when the trees, benches and fountain are not safe.

Western Avenue needs raised triangular islands or splitter islands on both approaches (similar to Conn. Avenue islands although not landscaped) instead of the flexible poles that block pedestrian access and safe refuge.

DDOT must consult with experts in circle design (such as Joe Bared) who understand the traffic engineering challenges that circles present. This is not a traffic intersection but a circle and those involved in designing solutions must respect that circles were never intended to be signalized. First introduced in 1905, circles were designed to move large amounts of traffic safely and efficiently through various interconnecting points. Signalizing circles disrespects their inherent design. Circles are safer without signals.

Has DDOT done any of this?

l. Perform Traffic Safety Analysis of Chevy Chase Circle Accidents—worse accidents can occur when signal stops traffic inside Circle for signals. Different kinds of fender-benders and signal-related accidents will occur. Circles were never designed to have signals inside. They were designed to eliminate the need for signals. Three jurisdictions (DC, MD, Park Police) handle accidents depending upon where they occur. What are their statistics?

2. Perform a Time Delay study—signals could create worse delays than currently exist.

3. Do Computer modeling on the impact of signals.

4. Consult with experts on Circles such as Joe Bared who edited the book on Roundabouts. Signalizing Western Avenue at Chevy Chase Circle is more complicated than signalizing a traditional four-way intersection. DDOT’s January 2002 study seems to treat Western as a four-way intersection. It is not! A signal warrant study is not applicable to a Circle.