Monday, September 14, 2015

Slowing Cars with a Bucket of Paint

I’m often disappointed with the slowness at which I think.  Given enough time, I can assemble logical thoughts just fine, but it takes longer than it seems that it should.

All of us come home from occasional parties frustrated by bon mots that popped in our heads ten seconds too late.  But there times when the key facts to a problem are in front of me for a half hour or more, a problem to which I know the perfect urbanist solution, and yet the pieces don’t fall into place until the opportunity to interject the solution has passed.

As a case in point, I recently sat through a public hearing on a proposed apartment project in Petaluma.  An element of the project was a road diet along the frontage, converting a current four-lane road into a two-lane street, with a center turn lane and two 12-foot travel lanes.  The width left over after the diet would be used for a new parking lane and for wider bike lanes.  In general, I supported the concept.

There was extended public comment on the apartment project, probably over an hour, during which the neighbors mostly expressed their opposition to the project.  Although not expressed as frequently as concerns about parking sufficiency and building massing, a recurrent theme was the speed of traffic.  Neighbors recounted their fear of crossing the street and their unwillingness to allow their children to play near the street.

In keeping with typical public hearing behavior, it’s likely that the situation was exaggerated.  Personally, I’ve driven the street a number of times without noting any abhorrent traffic patterns, but it’s also likely that concern had at least some basis in fact.

And yet it was only at the end of public, as the Planning Commission Chair raised the gavel and looked about the room asking if anyone else wished to speak, that the penny finally dropped for me. 

It’s well-established that reduced traffic lane widths result in slower traffic speeds.  As replacements for the long-time standard 12-foot lanes, 11-foot lanes or even 10-foot lanes can calm traffic noticeably.  And yet here I was, watching a public discussion of a proposed road diet that called for 12-foot traffic lanes in a neighborhood that was loudly bemoaning excess traffic speeds and I was sitting on my hands.

I was still marshalling my thoughts, trying to decide how best to phrase my lane width insight, when the gavel dropped.  Nuts, another opportunity missed.

My failure was particularly galling because several articles on land width have recently crossed my desk.  A study presented to the Canadian Institute of Transportation noted that accidents are minimized when traffic lanes are 10 to 10.5 feet in width.

Better Cities and Towns reported the same study and complemented it with the information about pedestrian deaths being reduced at lower car travel speeds.

Writing for StrongTowns, Rachel Quednau noted that most crosswalk warning systems don’t function as well as hoped, so lesser lane widths, resulting in slower travel speed and greater opportunities for drivers to react, is the only solution.

Most persuasive was a piece from CityLab, written by walkability expert Jeff Speck, that summarized the current data on lane widths.  Speak also linked a study from the National Association of City Transportation Officials with an even more rigorous assessment.

Before dipping further into the role of lane width changes, I should offer a refresher on speed limits.  Speed limits are set based on how fast cars travel in the absence of posted speed limits.  City Engineers are empowered to change those results, but only slightly.  So the primary determining factor for a speed limit is how the driver perceives and responds to the road design.  (I wrote more completely on this subject, including a fun and pertinent North Bay anecdote, in an earlier post.)

Setting speed limits based on actual speeds may seem an odd approach, but with a thought experiment the reasonableness quickly becomes apparent.  Imagine a new freeway with broad sweeping turns, wide shoulders, perfectly smooth pavement, and plenty of bridge clearance.  Now imagine that a sign is posted at every on-ramp limiting driving speed to 35 mph.  What would happen?

There would be two streams of traffic, one responding to the posted limit and driving perhaps 35 to 40 mph.  And another stream that didn’t see the signs and is driving 70 to 75 mph or even faster because that’s how drivers respond to freeways.

 And when two disparate streams of traffic try to occupy the same roadway, accidents will happen, potentially a lot of accidents.

Admittedly this is an extreme case, but something similar would happen if a 25 mph sign was posted on a road that was designed for 35 mph.

 The paradoxical result is that, when someone complains to city hall that drivers are speeding through their neighborhood, a correct response, and the most convenient and easily implemented response, is to raise the posted speed limit.

I dined with a cousin last evening, a fun dinner at a sidewalk café on a fall evening with a slight chill in the air.  During the meal, she told of a neighbor who was embarking on a crusade against speeders on the collector street passing by the side of his home lot.  Being my typical slow-witted self, I failed to note to my cousin that her neighbor was effectively arguing for a higher posted speed limit on the street.  However, I’ll forward this post to her.  Whether she shares it with her angry neighbor is up to her.

The other, less convenient option available to city halls is to change the drivers’ perception of the street.  This option is the source a StrongTowns blog that may be the most delightfully pithy blog post ever.  I highly recommended spending the necessary 15 seconds to digest the absurdity that it highlights.

If changing the drivers’ perceptions is pursued, a number of tools are available, from stop signs to speed bumps to street trees.  But in most cases the easiest and most cost effective is to reduce lane widths.  On streets that are already striped, fog lines can be pulled in to reduce driving widths.  (I’ve previously suggested this for B Street in Petaluma.)  On streets that aren’t striped, a dashed line down the middle can serve the same function.

Although it’s a simple and effective solution, it also seems a solution that fails to gain traction as well as it should.  In fact, people often seem remarkably uninterested in it.

I’ve had conversations with groups who were agitated about speeding and arguing for increased law enforcement, speed bumps, flashing lights, more stop signs, etc.  After I patiently explained why modified lane striping was the best and perhaps only real solution, they generally seemed mollified, departing quietly and unwilling to broach lane painting to city hall, ensuring that their problem remained unsolved.

It seems that mobilizing law enforcement or inducing city hall to spend lots of money are the only problem solving approaches that fire our enthusiasm.  That disappoints me.  We should revel in low-cost, simple solutions, but we don’t, at least for traffic speeds.

Which brings me around to one of the reasons for this post.  There will be a meeting on pedestrian safety at the Petaluma Community Center on Thursday, September July 17 at 5:30pm.  I don’t recall what organization is hosting the event, but I’m planning on attending.  And perhaps I’ll have the chance to mention lane widths.

Back to the recent hearing, I may have missed my opportunity to make comments during the public hearing.  However, the Planning Commission deferred their decision, asking the applicant for additional information before rendering their judgment.  The continuing process won’t include further public comment, but there may still be opportunities to sway Commissioners.  I’ve already exchanged private thoughts with a couple of the Commissioners on lane widths and I know that several are occasional readers of this blog.  So I can perhaps make a difference even if I whiffed my first chance.

Better late than never.

For my next post, I have one more insight from the apartment project hearing to share, on the oddly tenuous relationship between effective project planning and the Goals in General Plans.

As always, your questions or comments will be appreciated.  Please comment below or email me.  And thanks for reading. - Dave Alden (

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