Preventing Bicycle Fatalities at US-36 and Violet

Ghost Bike at Violet and US-36 in North Boulder by Zane Selvans on flickr

Two bicyclists have been killed at the intersection of US-36 and Violet Avenue since 2009. The most recent was TJ Doherty, on July 24th, 2012. Both cyclists were headed southeast on US-36, and were hit by cars traveling northwest, making left turns onto Violet. In this area US-36 is just outside of Boulder’s city limits, in the county, but it’s the Colorado Dept. of Transportation (CDOT) that’s responsible for it. Looking at the aerial view below we can explore why this intersection might be particularly dangerous for cyclists.


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Northwest bound vehicles on US-36 have a dedicated left turn lane, and no obligation to stop before making their turn. The angle that Violet Ave. makes with the highway is quite oblique, meaning that it can be taken at high speed, and because US-36 has a speed limit of 55 mph in this area, cars often will take it at high speed if they don’t see any oncoming traffic.

From a southeast bound bicycle’s point of view, there’s no obviously correct place to be on the road, if they’re planning to proceed through the intersection. The shoulder on the west side of the road narrows to a few inches, and it’s to the right of a right-turn-only lane. If you ride all the way to the right, you risk a vehicle turning in front of you onto Violet. Your intent to continue through the intersection is also unclear to oncoming traffic. Most cyclists instead take a position that’s well within the right turn lane, to prevent right-turning vehicles from passing them and immediately turning right in front of them. However, this lane position still leaves their intent ambiguous to oncoming traffic. Alternatively, you might choose to straddle the line separating the through travel lane and the right turn lane. This makes the bike relatively visible, and more clearly conveys the intent to continue through the intersection, at the expense of potentially sandwiching the cyclist between right turning vehicles and very fast moving through traffic. If the cyclist instead chooses to behave exactly like a motor vehicle, moving into the through lane of traffic, the very large difference in speed between the bike and the other vehicles in that lane creates a hazard. Thus, there’s no right place for a cyclist to be on this road if they’re planning to continue through the intersection.

When we combine the unavoidable ambiguity of the through cyclist’s intent with the very high left-turning speeds of oncoming traffic, we have a recipe for disaster. A recipe which has killed two people in three years.

The particular geometry of this intersection is really just the proximate cause of death. The larger issue is the proximity of a fast, high volume road to a relatively dense residential neighborhood. North Boulder has become a town center in its own right in the last 5-10 years, and the re-development is ongoing, and has been highlighted as one of the most successful redevelopments in the city. Traffic counts between Jay and Broadway on US 36 indicate that more than half the cars the road carries are accessing north Boulder. Boulder has done much better than most towns at preventing the introduction of large volumes of high speed traffic into its urban fabric, but this is one place where that friction exists. There are no plans to mitigate this friction. The area to the northeast of US-36 here is part of the Area III Planning Reserve. Plans for its eventual development have been contentious, and at the moment it seems likely that it will remain rural for quite a while. This half rural, half residential context for the highway, and the road’s location outside of the City’s jurisdiction and status as both a US and Colorado state highway makes it likely that it will continue to have near freeway like design criteria applied to it.

Despite that, there’s still room for improvement, and even before the most recent fatality, the intersection was slated for renovation. Using federal TIP funding obtained by the city, the intersection will be re-aligned to more closely resemble the one at Yarmouth, just to the north:


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This should result in much slower turning speeds for the northwest bound drivers, giving them more time to see what’s going on in the intersection, and avoid potential collisions.

However, those changes will not take place until 2015. With that in mind, the Community Cycles Advocacy Committee (CCAC) organized a meeting with CDOT at the site to talk about ways we might make the intersection safer in the interim. Because the road is a state right-of-way sandwiched between city and county lands, we made sure we had representatives from all the relevant jurisdictions. We had GO Boulder‘s bike/ped person, Marni Ratzel; Boulder traffic engineer Bill Cowern, Lesley Swiren from the county, and from the CDOT office in Greeley we had traffic engineer Larry Haas.  We had most of the CCAC as well, including advocacy director Sue Prant, board member Ann Haebig, north Boulder resident Chuck Brock, long time Boulder bicycle advocate Kurt Nordback, Fred Ecks, and myself.  I suppose I was also representing the city in some capacity as a member of the Transportation Advisory Board.

CCAC Meeting Larry Haas from CDOT by Zane Selvans on flickr

Having looked at the scene and the crash reports ahead of time, we (the CCAC) had a couple of suggestions for improving its safety.  The first was to lower the speed limit.  Just to the southeast of this intersection US-36 transitions to being slightly more integrated with the city, and the speed limit drops from 55 mph to 45 mph.  The more recent of the two crash reports incorrectly listed the speed limit at this intersection as 45 mph, and we thought it might be straightforward to simply move the speed limit signs up by one intersection, to include this one until it’s re-engineered in a couple of years.  Our second suggestion was to carve out space for a bike through lane between the right turn lane and the car through lane, so that there’s a designated space for through cyclists, that makes their intent clear and increases their visibility.  Most of the riders who came through the intersection while we were standing out there were willing to take up the right turn lane, so hopefully a significant proportion of them would be willing to use that designated space if it were provided.  We also suggested striping the lane all the way through the intersection, and potentially painting it solid green, to create an obvious visual cue to northwest bound drivers that there’s the potential for conflict with bikes proceeding into the intersection, somewhat along these lines:

Let me first say that CDOT, to their credit, was very responsive when we requested a meeting.  They got right back to us and within about a week of our first e-mail we were out at the intersection together.  They also provided us with copies of the crash reports.

In retrospect, we probably should have known better than to suggest lowering the speed limit, as several of us already knew that in effect transportation agencies do not set speed limits.  Drivers set speed limits.  This is true in at least two ways.  First, the numbers you see on speed limit signs along the side of the road are usually the result of speed studies, not policy decisions.  Someone comes out with a radar gun and clocks the speeds of the cars for a while.  From the distribution of observed speeds, you can see what speed drivers seem to consider reasonable.  The top end of the distribution is cut off, usually at the 85th percentile, and that cut off speed becomes posted speed limit.  Second, it turns out that drivers are very insensitive to posted speed limits.  People tend to drive as fast as the physical road suggests is safe (safe for the driver, that is).  Wide, straight, smooth roads with large clear areas on either side say “drive fast!” no matter what the posted speed limit is.  In California, the 85th percentile rule is actually law — transportation agencies have no leeway in whether or not to use it to set the speed limit.  In Colorado it’s not law, but traffic engineers are reluctant to deviate from the practice, because there is a small segment of the population that actually looks at the posted speed limits, and when you mix those people (driving slowly) with everyone else (driving the speed the road design suggests) you get rear-endings.

So Larry’s take on the idea of lowering the speed limit was that, if they actually did a study, the speed limit (as indicated by the 85th percentile rule) would be more likely to increase than decrease, which wasn’t really what we wanted.  Of course, it didn’t really matter much, since virtually nobody’s driving behavior was going to be changed either way.  The real solution, if we wanted slower cars, would be a costly re-engineering of US-36 itself for slower speeds.

CDOT Traffic Engineer Larry Haas talking with Sue Prant from Community Cycles by Zane Selvans on flickr

Our second suggestion, for a well demarcated through lane, was also dismissed out of hand initially.  First, because there was “no space” for a bike lane between the through travel lane and the right turn lane, and second because any paint through the intersection “would just get scraped off anyway” by snow removal equipment.

Now, if you look at the aerial view of the Violet and US-36 intersection above, you’ll see that southeast bound US-36 has a dedicated left turn lane, which lets drivers get from the highway onto (zoom out a little) a tiny dirt road that doesn’t go anywhere.  Nobody is using that left turn lane.  Similarly, on the northwest bound portion of the road, you’ll see an acceleration lane on the east side of the highway, allowing the non-existent traffic merging onto US-36 from the tiny dirt road to get up to the prevailing speed of traffic. These amenities are only there to support hypothetical future development, and altering them would require nothing more than changing the paint on the ground, which is relatively cheap and easy compared to pouring concrete or rolling asphalt. Clearly with two deaths already, the danger posed by the intersection is not hypothetical.

We further pointed out, to no avail, that solid painted bike lanes were being used in plenty of snowy places like Minneapolis, Minnesota, and that in any case this was meant to be a temporary treatment, mitigating the danger of the intersection until its re-engineering in 2015. But somehow, the communication seemed to be failing. All we were hearing was no.

Then Larry presented his suggested solution to us…

Watch for Bikes

Now, there’s nothing wrong with signage, but just about anyone who rides a bike in traffic will tell you that it doesn’t get you much in the way of behavior change.  Both of the drivers who killed cyclists at this intersection said they didn’t see the bikes.  A 2 foot wide sign on the far side of the intersection seems like a sad consolation prize in this context, unlikely to attract the necessary attention if drivers already aren’t seeing the other road users.  Additionally, there’s another sign which doesn’t just encourage generic awareness.  Left turning drivers actually don’t have the right-of-way here — they have to yield to all oncoming traffic.  This reality might be better conveyed with one of these instead:

Left Turn Yield to Bikes/Peds by Eric Gilliland on flickr

At this point, thankfully, Marni and Bill showed up and got involved in the conversation, as did a random elderly passer-by. The interloper shared his concerns that the current arrangement of the intersection would result in additional fatalities, and that something needed to change. He repeatedly pointed out that the behavior of cyclists in the intersection was hard to predict, and we all agreed… but it seemed that there was a lingering suggestion that the unpredictability of the cyclists was somehow also the fault of the cyclists. Larry Haas from CDOT echoed this sentiment, which raised the hackles (and some of the voices) of the bicycle advocates, who pointed out — again — that there is no right place for cyclists on this road today. It is not a complete street. The outburst created some temporary distance between Haas and the now 8 people surrounding him.

CDOT's Larry Haas talking with Boulder's Bill Cowern about the intersection of VIolet and US-36 by Zane Selvans on flickr

At this point Bill Cowern, the City of Boulder traffic engineer, engaged Haas more directly and constructively. Somehow having another traffic engineer suggesting to him that striping a painted bike lane through the intersection was both possible and desirable made the idea more palatable, and they started talking about where they could get the space from on the road, or whether it might be possible to do a shared right-turn through-bike lane, as we’ve got on 28th St. now, with dashed striping inside the lane (even without getting additional width from the other lanes on the road).  Lesley that the county has been considering vacating the right-of-way for the short dirt chunk of Violet Ave. on the east side of US-36, since the properties it serves are accessible via 26th St. just to the south, there’s virtually no use of the road today, and no concrete plans for development out there. Eventually Bill and Larry drove off together to take a look at the shared bike/bus turn/through lane on 28th St., and we all took a couple of deep breaths. A few of us rode down to Boulder Beer to unwind and debrief a bit.

The whole experience was a vivid reminder that outside our little bubble — even just a few feet outside it — transportation expectations and priorities are very different. Unfortunately what the state and the nation want are pretty different from what we want. All the more reason to overhaul our local transportation funding mechanisms to give us the means to pursue our own goals. It was also a good reminder that we have built a team of people, both within the local government and the citizenry that can effectively engage with and press for change from folks outside the bubble, and I’m happy to be able to play some small part in that process. The plan right now is to have whatever paint-and-signage solution we can agree on in place by later this summer or early this fall. We’ll see how it goes.

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2 Responses to Preventing Bicycle Fatalities at US-36 and Violet

  1. Zane Selvans says:

    After I wrote this up, somebody pointed me at this great conversation with a traffic engineer video on YouTube from the folks at the excellent Strong Towns initiative.

  2. This is the intersection you mentioned this morning? I normally avoid US36, but I took it from Yarmouth to Jay for a couple of weeks last month, to avoid construction on 19th. This intersection was a little nerve-wracking. I’d try to shadow the southbound cars as best I could so that those turning left wouldn’t get any bright ideas. The construction on 19th is complete (at least for now), but I may check out this intersection later this month to see how it looks.

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