Tamm Avenue Opening & Lane Shifts Revisited

MoDOGYesterday, the first small portion of the Highway 40 reconstruction project was completed. The Tamm Avenue bridge opened up to traffic six months to the day after the old overpass had been imploded. I attended the opening, and much of it was the mundane: the political speeches, the posing for the media, and the propaganda banner proclaiming “A Milestone Delivered” . However, there were some things that highlighted the uniqueness of the area: the unveiling of Bob Casilly’s reconstructed snake biting the bridge, turtle races on the bridge, a cute “MoDOG”, and a surprisingly poignant speech by Sunny Glassberg, who helped found Turtle Park.

At the same time, I was curious if six months of lane shifts had changed driver behavior around Tamm Avenue, which I highlighted several months ago in this video.

A summary of it all is in the video below.

By the way, the Post-Dispatch had a nice article in today’s paper about the overpass opening. It features a photo of my son keeping an eye on the wayward traffic on the highway below.

Update: Lane Shift Standards

Lane Shift guidelines In a previous post, I documented drivers’ behavior at the lane shift at Highway 40 and Tamm Avenue, which many of you agreed was dangerous. In looking for ways to make this area safer, I noted that the lane shift at I-270 and Dougherty Ferry used solid white lines for lane markers instead of dashed lines like at Tamm. It was much easier to stay in the lane with these bright solid lines. These two construction projects are handled by different contractors, so I asked MoDOT what standards they specify. I received a quick and professional response from MoDOT:

At the core of the issue, Federal Highway’s Manual on Uniform Traffic Control Devices dictates the guidelines we use for lane shifts. If you have a dramatic lane shift, or one that requires a quick traffic movement, the manual dictates using solid lanes. If the lane shift is a little more gradual, it is acceptable to use the dashed lines. Often times, the determination on the traffic impact of a lane shift is made by the person designing that particular traffic movement. So, though MoDOT doesn’t provide guidelines per se (since we use Federal mandated guidelines), we will adhere to, and ensure contractors adhere to, those guidelines. As with every guideline, though, there is some area for interpretation.

If you’d like to read the guidelines on lane shifts for yourself, here are links to the notes and the details . The guidelines seem to lean toward using solid lines as lane markers, but does leave it open to some interpretation.

At MoDOT’s recommendation, I will submit a comment form to the Highway 40 project team, asking them to look at the video I shot to see if solid white lines might be an improvement in this area. I’ll keep you up-to-date on their response.

Update 6/22:

I received the following response from the I-64 Community Relations team. They are not considering use of solid lane lines at Tamm, for reasons they describe below. So the best advice for now is to stay vigilant when driving through these lane shifts.

EB I-64 at Tamm, the traffic shift is fairly minor, and the use of solid lines is not recommended. WB I-64 at Tamm the lane shift is more noticeable on the inside lanes and very minor on the outside lane. This is caused by the lanes narrowing from 12′ to 11′ in the work zone, with the outside lane experiencing the smallest shift.

At this time, the use of solid lane lines between each lane is not being considered. One of the main reasons for this is that the transition points for the stripes use curves opposed to hard angle points and taper-style lane shifts. The taper lane shift is shown on the MUTCD excerpt on your blog; meaning, there are hard angle points where the stripes force traffic to turn abruptly to remain in their proper lane. The Tamm workzone lane lines use curves allowing for smooth transitions around the work zone. Plus, the striped curves are designed to handle 55 mph interstate traffic, so no speed reduction signs are necessary. By designing the traffic shift to current speed limit, the need for solid lane lines between lanes is also reduced.

Lane Shifts and the Loss of Common Sense

You can’t drive far on St. Louis highways today without encountering a lane shift due to construction. On Highway 40 alone, there are 3 lane shifts from Kingshighway to I-170. As I drive through these lane shifts, I can’t help but notice just how challenging it is for many motorists to stay in their lane. I suspected that if you were to watch traffic at one of these lane shifts, you would see many dangerous situations in a short time. Little did I know how true that would be. See the video below. . .

It seems that drivers are just not paying attention. They’re zipping down the road, following the car ahead of them, unaware of the signs for the upcoming lane shift. The next thing they know, they’re across the dotted line. We tend to assume that the lanes follow the seams in the concrete and asphalt — which typically do line up with the painted lines — but can we not pay a little closer attention?

What are your thoughts? Can anything be done to make these seemingly simple lane shifts safer? Share your ideas by leaving a comment.

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