Illustration for article titled Who is the best authority to contact for interpreting Traffic Control Devices?
Image: Manitowiki

Traffic Control Devices (TCDs) come in many forms. Road markings, signs, traffic signals, VMS boards, etc. And they’re usually pretty easy to understand. But on the rare occasion that they’re not, whom should one contact for interpretation?


Local road commission? State DOT? Local police? State police? A lawyer specializing in traffic law? In theory, they should all offer the same advice. But what if they offer differing opinions? Who would be the most knowledgeable and most authoritative?

I’ve got a few hard questions that I’d love to get resolved, but here’s just one example of a case that I struggle with on a daily basis: “right lane ends; merge left”.

Illustration for article titled Who is the best authority to contact for interpreting Traffic Control Devices?

When/where exactly is the right time/place to merge left? Of course adjustments need to be made when merging among other drivers, but surely there’s an ideal point for merging when the road is clear? If the speed limit begins precisely at the speed limit sign; is there a similar rule for merging? Does the yellow coloring of these signs render them as nothing more than unenforceable advisory signage, as opposed to the white backgrounds used on regulatory signs?


In my area, most drivers seem to consider it prudent to merge as early as possible, securing the Unending Lane miles before the merge point. But this becomes a big problem when the left/inside/passing lane becomes backed up, extending the traffic jam twice as far as it otherwise could be. It even becomes a problem before you reach the actual congestion, as timid drivers who like to drive 5-10 mph below the posted speed limit jump into the lane way too early.

Sadly, my state (MI) does not mandate zipper merging like Minnesota does. (Update: my bad, MN hasn’t actually made it a statewide law yet. LAME) Right-of-way still belongs to whomever is already in the lane, and many will fiercely defend that R-O-W, blocking what they perceive to be unfair attempts to get ahead.


The main focus of my question revolves around the conflict created by this type of lane drop in view of our left lane laws. According to MCL 257.634, we are to keep right, driving “in the extreme right-hand lane available for travel”, leaving the left lane open for turning left, passing slower vehicles, and rush hour traffic volumes. Slower drivers are to stay in the right-most lane, and faster drivers are to return to the right-most lane at their earliest opportunity. The right/curb lane is supposed to be our default lane of travel, but the threat of an upcoming lane drop really screws with everybody’s willingness to drive in that lane at all.

To help relieve this stressful and awkward situation, two solutions come to mind:

  1. Replace the signs with “LEFT lane ends; merge RIGHT” ones, and paint the road lines accordingly
  2. Mandate and enforce zipper merging at the merge point

(Personally, I’d like to see both happen)

Funny thing is, our Department of Transportation is already well aware of the benefits of zipper merging, thanks in part to this 84-page analysis from Wayne State University submitted to MDOT over a decade ago. It’s a far superior and way more efficient method than what we have now, but legally speaking, right-of-way still technically belongs to traffic already in the unending lane. No matter how much MDOT encourages and experiments with zipper merging, the rest of the state does not require it. And if they do enforce it, it’s only happening where MDOT has placed signs ordering zipper merges at specific construction zones. They know it’s a good idea, but have yet to make it official statewide.


But the choice of signage deserves attention too. Seriously, why bolt up a W4-2R sign, when it would be just as easy to bolt up a W4-2L sign instead? And if the right lane doesn’t line up with the single remaining lane after the merge point, all it takes is a little paint on the road to direct the lane shift. Note how this broken line in the image below aims to keep traffic to the right instead of letting them continue in a straight line. A similar diagonal line could be used prior to a lane drop merge point to help show left-laners that they are running out of room.

Illustration for article titled Who is the best authority to contact for interpreting Traffic Control Devices?
Image: Alchetron

Anything would be better than a system that literally, directly rewards left-lane hogging. But I digress... Until we get better road/TCD design, we need clarity on how the current system is actually supposed to work. Who should be my first choice in directing these questions toward? The DOT or road commission in charge of road design? The cops who enforce traffic law? The lawyers who study the verbiage on the books?

(Again, lawyers, police, and road authorities should theoretically all offer the same advice, but here’s a quick story to explain my doubts: I once asked a local police officer about our left lane laws and he denied that there was any problem with cruising indefinitely in the left lane. I later received a totally different answer from a state trooper. The apparent conflict has shaken my faith in getting a straight answer that I can trust.)

Share This Story

Get our newsletter