Traffic Calming

I am a member of the Sebastopol General Plan Advisory Committee. Circulation was the topic of our meeting last month. It was a robust conversation for 3.5 hours, and we still managed to omit large topics, like transit. But it gave me another opportunity to look at circulation issues in Sebastopol. And while there is plenty to talk about, I’d like to discuss traffic calming today.

Two state highways intersect in the middle of Sebastopol. Highway 12 actually starts in the center of downtown and travels east. Highway 116 travels north/south and is Main Street in the center of downtown. North of downtown 116 is known as Healdsburg Avenue and is the primary route to the north. South of downtown it is South Main Street and is one-way in the southbound direction. Posted speed limits are 25 mph on Main Street downtown and 30 mph on both Healdsburg Avenue and South Main Street about 4 blocks south of downtown. In my observation, and based on comments from many other committee members, traffic speeds are often exceeded along most of the length 116 and the result is that these streets do not feel like safe places to walk or bike. There are several reasons for this.

Sebastopol Aerial

Both Healdsburg Avenue and South Main Street are very straight (actually Healdsburg Ave. has a couple slight bends as you can see in the photos, but given it’s width and the slope you can see along it’s entire length). People have a tendency to drive faster on straight streets because you can see far ahead. Streets with bends tend to slow drivers down as you can’t see what’s around the next corner and you need to be prepared for the unexpected. This is evident on the segment of 116 that serves as the one-way northbound approach to downtown. The street is Petaluma Avenue and it has several bends and changes in elevation. Traffic definitely drives slower on this street than on Main Street which is just a block away and is one-way in the southbound direction.

In addition to being very straight, Healdsburg Avenue also slopes down most of it’s length heading towards downtown which encourages cars to speed up as they are heading into downtown.

Healdsburg Ave. is configured with a center turn lane, single travel lane in each direction and parallel parking on each side (parallel parking is omitted at some locations). The curb to curb width varies from 52′ to 54.5. Travel lane widths vary from 12′ (which I believe is the Caltrans minimum) to 20′ (yes, 20′!) at the east end where there is no parallel parking. Most of the driving lane width is in the 12′-14′ range.

Healdsburg Ave. at intersection with Main St., looking west

Crosswalk on Healdsburg Ave. It would be nice if the white line was indicating a bike lane, but it’s not. Not sure why it’s there

Healdsburg Ave., near the top looking east

The configuration of S. Main starts as 3 lanes all in the southbound direction at Bodega Ave., but one lane is dropped after a block so the bulk is 2 lanes. Where 3 lanes, the lane configuration is 13′, 12.5′, 13′ with 8′ parking lanes for a total width of 54.5′. Where it goes to 2 lanes each lane is 17′ wide with 8′ parking lanes (curb to curb 50′).

Looking South on Main Street – How fast would you want to drive here? The speed limit is posted 25 mph here and changes to 30 mph a block south of this location. Driving lanes are 17′ wide.

The lane widths of both Healdsbug Ave. and S. Main allow for much faster driving than the posted speed limit. While I don’t have a radar gun it is obvious as a pedestrian walking these stretches that vehicles are traveling over the speed limit. It’s also obvious when driving. I’m very aware of the speed limit and the environment and have to be extremely alert when driving these streets so as not to speed. And it is also obvious to the police department who have several spots they like to park to catch speeders. The police department also uses those portable speed detectors that display your speed. (You know a street is designed for a speed far greater than it’s posted speed limit when they have to pull these out.)

Speed Detector – not being used today

Both street segments have been the recipient of ‘Street Smart Sebastopol’ crosswalks which typically include bulb-outs, pedestrian crossing signs, flashing lights and sometimes include in-roadway lights and colored crosswalks (although the green color of the crosswalks does not differ much in value from the regular asphalt). While I believe these have helped in making drivers more aware that they are in an environment shared with pedestrians, it’s really not enough to keep speeds low.

Street Smart Sebastopol crossing of Main Street and Calder

Main Street crosswalk at Willow

One idea for slowing traffic I believe deserves to be explored, would be to create a raised intersections between Healdsburg Avenue and Main Street and their respective side streets (See the National Association for City Transportation Officials guidelines for raised intersections here). The street would be ramped up at intersections ahead of the crosswalk, to the sidewalk level. The raised section is continued to the opposite side of the intersection. This allows pedestrians to cross without a curb ramp and encourages drivers to slow down as they travel over the raised intersection. Raised intersections are often constructed of pavers or stamped and/or colored concrete/asphalt to bring attention to themselves. This type of installation prioritizes the pedestrian over the car which is rare in our urban places. It may be a bit much to include at each intersection with Healdsburg Ave. or Main St., but even a couple on each length of street would limit a driver’s ability to speed up much in between raised intersections, keeping vehicle speeds lower and safer for everyone.

When the lanes are wide and streets are straight drivers are more likely to engage in other distracting behaviors (like texting) and take their minds off the activity at hand which is driving a car. By introducing an unexpected piece of infrastructure like a raised intersection you cause drivers to pay more attention to their environment, they can’t just go into autopilot mode on the wide straight street.

To be honest, I’ve never seen a raised intersection used on a busy main street like I’m proposing, but I think they would definitely serve to keep speeds in check. If would be great to see some examples. (If anyone has any please forward to paul@fritzarchitecture.com.)

It has been shown that pedestrian fatalities are much reduced when cars are traveling at 25 mph or less. The design of Healdsburg Ave. and Main St. allow for much higher travel speeds, and have been the sites of bad collisions between pedestrians and cars (there was 1 fatality at a crosswalk on Healdsburg Ave. earlier this year). We’ve been prioritizing cars in the design of our streets for a long time now. We need to recognize the importance of pedestrians and other non-motorized street users in street design and raised intersections is one way to do that while at the same time reducing traffic speeds and hopefully accidents between cars and people.