Posts about Roundabouts

Just counting collisions misses important facts

How many of these were just property damage? Minor injuries? Major or disabling injuries? Fatalities? It's important to keep in mind that in the District, the number of traffic fatalities each year can usually be counted on one hand.

Some road designs reduce severe crashes but potentially increase minor collisions. For example, many areas are finding "modern roundabouts," the small circles without signals, to be a fantastic alternative to huge intersections with multiple turn lanes or freeway-style interchanges. They move traffic more smoothly and safely, but minor collisions are more common while major ones are less so. Limbs and lives are more valuable than bumpers.

On the flip side, bad road design can contribute to collisions. Short yellow lights or poorly-coordinated signals can lead to red light running. Poor signage or markings can confuse drivers and induce sudden movements. And what about maintenance? Crumbling roads can damage cars, potentially adding to the collision tally if the person places a claim with Allstate.

What about other modes? If the methodology counts based on Allstate claims, it might undercount pedestrians or cyclists being struck who might not have insurance. That could penalize cities with good ped/bike safety practices. On the other hand, areas with more walking and bicycling can require more attention from drivers than areas with long, straight, very wide roads where nobody dares walk, and the rate of cars touching each other might be higher despite the many other benefits of these more lively places.

We also can't let Allstate's and the press's repeated usage of the word "accidents" pass by. When we have thoroughly vetted users traveling on context-sensitive travelways being taken aback by sheer acts of God, then these can be genuinely called "accidents." Until then we have crashes, collisions, and oft-unintended unions of flesh and metal.

Maryland actually has the best drivers?

Rankings always seem to grab the most headlines, and this is useful data for Allstate to release. But it's always important to keep in mind that statistics are very finicky. A quick analysis (XLS) shows that the rankings vary enormously based on what gets factored in.

Allstate ranked areas based on the average time between claims per driver. If we adjust these numbers to equalize vehicle miles traveled per capita, then Maryland comes out with the fewest collisions. So this story could easily have also borne the headline, "Maryland drivers the best in the nation." Are they the best or among the worst? We don't really know enough to say.

What can we do?

Even though it's disputable whether the area's drivers are really the worst, most people aren't contesting or doubting it. Rather, they're nodding in agreement and cheering it on among the blogosphere. We seem to agree that we're lousy drivers.

So perhaps we don't even need thrown-together numbers to tell us that? If we just assume our region is full of bad drivers, what's next?

We could look at licensing regulations, and do more to ensure those who get or keep licenses have a decent competency to drive. However, any weeding-out is politically difficult. What if we were the ones being weeded out? In one study, the vast majority of drivers said they thought they were above average. That's statistically impossible if there's anything close to a normal distribution.

What about enforcement? We could detect and punish more of the particularly unsafe behaviors on our roadways. Automated traffic cameras are an effective solution, but they too encounter resistance. Plus, as with the roundabouts, cameras might actually make a region's Allstate ranking worse while saving lives. Statistics on red light cameras also show that they often lead to more minor low-speed rear-end collisions while reducing the much more dangerous side-impact crashes.

Finally, we can design roads for the safety of all users, motorized and not. There's often pressure to design for higher speeds and then jurisdictions set lower speed limits when people get hurt. We can do more to build in the visual cues that help people slow down, pay attention, and reduce crashes, or at least reduce the most severe ones.

Any of these take some political courage. Will our region's leaders stand up to take action to improve DC's ranking on this survey or, better yet, on the more important statistics of fatalities and severe injuries?

Option 3 stands out as the best option. Its most notable feature is to reconfigure the intersections with Vermont Avenue and Sherman Avenue to traditional right angles. Currently, the intersections are designed like highway ramps to aid drivers in speedy turns between the avenues. As expected, when you engineer a road for fast driving, people will drive fast regardless of the speed limit signs.

Vermont Ave & Florida Ave. Left: Now. Right: Option 3 proposal.

To discourage speeding, option 3 curves both of these avenues to intersect Florida Avenue a right angles. This will require sharper turns that will calm traffic and reduce the distances pedestrians must traverse to cross the avenues.

The elimination of the high-speed turn lanes creates the opportunity for two small plazas at these intersections.

Option 3 also reduces the amount of impervious surface (orange) and allows for a planting strip with trees on the east side of Florida Avenue just south of Vermont Avenue. Furthermore, it includes for curb extensions that reduce the distance pedestrians must spend in the path of traffic when crossing the streets.

Bike lanes will extend from Sherman Avenue to 9th Street and will connect the bike lanes on V Street, W Street, and Sherman Avenue.

These changes are very welcome, but there are several regrettable omissions. The intersection at V Street lacks a crosswalk on the north side, as does the north side of the intersection of Vermont Avenue. The intersection with W Street lacks any crosswalks for crossing Florida Avenue at all.

To cross Florida at W, a pedestrian will have to detour nearly 900 feet to and from the nearest crosswalk, or cross without a marked crosswalk. Under DC law, any edge of an intersection is still a legal crosswalk, but by avoiding striping one, DDOT is sending a signal that it isn't designing the intersection to be safe to cross.

W St & Florida Ave. Left: Option 3. Right: Author's proposed improvement.

As Howard University increases the number of students living on campus while encouraging walking and biking, the city must build the infrastructure that makes walking safer, easier, and more comfortable.

Curb extensions and crosswalks at W Street would provide an excellent pedestrian accommodation, yet options 1 and 2 show one isolated curb extension at W Street and option 3 shows none.

In 2009, DDOT agreed to add a crosswalk to a Fort Totten intersection which had a missing leg. Including safe crossings at all intersections in street designs should be one of the ways DDOT follows through on its "complete streets" policy.

Another disappointment is that DDOT's 3 design proposals ignore the roundabout envisioned in the Office of Planning's Duke Plan.

Left: Intersection of Florida and Sherman today.
Right: Older plan for the intersection with extended Bryant Street.

A roundabout would lie at the intersection of Florida Avenue, Sherman Avenue, and a newly created Bryant Street, which would be constructed on a DC-owned parking lot that lies east of the intersection.

DDOT staff will present this design and take questions at tonight's meeting of the ANC 1B Transportation Committee. The meeting starts at 7 pm at the Thurgood Marshall Center, 1816 12th Street NW.

• This circle has a series of lights, which effectively kills any chance of it being a true traffic circle. This also makes merging into the circle difficult, because given the light cycle the circle may be filled with stopped cars which often create their own lanes.
• Route 50 travels through the center of the circle, but there are no left turns allowed and the signage indicating this is quite confusing. Drivers who wish to turn left onto Lee Highway or Old Lee Highway have to first turn right and then proceed through the circle, stopping at the light at route 50, from which they just turned off.
• To add to the confusion, left turns from Old Lee Highway or Lee Highway onto Route 50 are allowed and encouraged.

At least the pedestrian access issue has been solved. After some mysterious construction, pedestrian crossing signals have been installed on the right hand turn lanes onto and off from Route 50. This is a literal step in the right direction, but there is still a long way to go to make this circle something useable and safe.

This circle is near the border of Fairfax County and Fairfax City and could be treated as a celebrated entry into Fairfax City; this could be achieved by restoring this to a real roundabout, with lights regulating pedestrian crossings and entry into and out of the circle and creating a park-like center with a statue or fountain similar to many of the DC circles. If the traffic along route 50 needs a direct access to the other side of the circle a below grade ramp could be installed; there is already precedent for this treatment in Fairfax County at the intersection of Fairfax County Parkway and Route 29. However, do not believe that an underpass would be necessary. During rush hour traffic crawls in any case, and at all other times of the day, the local 35-mph speed limit should be easy to maintain in a properly timed and lighted DC-style circle.

A real circle here would solve many of the problems highlighted above. This new traffic pattern would be easier for drivers and safer for pedestrians. The break in the continuity of Route 50 would help emphasize the change from Fairfax County to Fairfax City. In addition, the shopping centers surrounding this circle attract a decent number of pedestrians, a park-like circle would provide them with some easily accessible green space.