I-94 Congestion: A Simpler And Safer Solution?

The congestion on I-94 heading towards St Cloud, particularly on sunny Friday afternoons, can be infuriating. It’s understandable that a lot of people are calling for ‘something to be done.’.

The quick reaction of politicians and others is a call to widen the thing—$30 million for another lane. Certainly that is the solution, they think.

There are a few concerns with this approach. First, we’ve never yet built our way out of congestion. We add roadway and, within a short time, (often just four years according to some studies) the problem is just as bad as before.

Second, widening one section of road often just pushes the problem down the road—literally. We might soon be hearing calls for widening further along 94, expanding 15 through St Cloud, and more.

Third, this is another few million dollars we could use elsewhere, like dealing with the all day every day congestion and fatalities in the Twin Cities that impact more individuals and businesses every day.

There’s also a question of safety (hint, with the same number of daily vehicles, which is safer and faster: a 4-lane highway in Europe or a 6-lane highway in the U.S.?).

There’s a possible solution that won’t cost $30 million, can provide relief immediately instead of five to seven years from now, won’t require a year or two of construction headaches, and will increase safety instead of decrease it.

Phantom Jam

Here’s what happens on a typical Friday afternoon on I-94. Someone drives slower than others in the left lane and a few cars pile up behind him waiting to get by. This micro jam of cars is called a platoon by traffic engineers. Platoons like this are inefficient use of the roadway and their tightly packed nature and enraging of drivers can be quite dangerous.

Once the lane blocker at the head of the platoon moves to the right, or everyone behind does to get around him, the platoon moves forward and breaks up. For these drivers it is a bit frustrating, but usually results in only a minor slowdown.

However, there’s another platoon lined up behind another lane blocker a few minutes behind this one and another behind that. Over the course of about 20 minutes, in the early afternoon, the gaps between these platoons get narrower and narrower until one platoon comes up on the rear of the platoon in front of it and whammo, you have the beginnings of the day’s phantom traffic jam. And it all started with the left lane blocker who’s now happily 30 minutes ahead of the jam they helped to start.

If you are a math or physics minded person, this behavior has been modeled by MIT and others with Poisson Distribution and Fluid Dynamics.

For those smart enough to studiously avoid such things, let’s watch a video:

Now, assume every car on I-94 is moving at a constant 80 mph (yes, it’s possible in a perfect world, perhaps such as if every car had a radar based dynamic cruise control to keep you exactly ten feet behind the car in front of you). One car brakes for just a very brief moment, which causes the car behind to brake, and so forth. Each car brakes just a little more than the one in front and so about the 80th car brakes to a stop and soon there are 50 cars stopped and jammed up behind number 80. This jam of stopped cars will grow and move backwards through traffic, sometimes for miles.

Someone blocking the left or middle lane has the same effect. One engineer describes the resulting jam as a shockwave moving backwards from the lane blocker.

We may not be able to prevent this completely in really heavy traffic, but we can likely reduce it quit significantly.

Lane Discipline

Lane Discipline is using the lanes of a roadway in the most efficient and safe manner as possible and is usually summed up as Keep Right Except To Pass.

A huge potential benefit of a four-lane highway, such as I-94, isn’t just to double the capacity of a two-lane rural roadway by having two lanes in the same direction instead of just one, but to multiply the capacity much more. Allowing faster drivers to quickly move around others and then get back in to the flow of traffic allows these drivers to utilize roadway capacity that is otherwise unused.

Instead of that driver being in front of you, they are now well down the road and not impacting you. You have more space to the car in front of you and are more comfortable. They are filling an unused gap. And this hasn’t cost anyone anything.

Our lack of lane discipline eliminates this benefit. Instead of getting perhaps a threefold increase in capacity by building a four-lane highway in place of a two-lane rural road, we only get about a twofold increase.

Lane blocking makes our highways more dangerous and less efficient for everyone.

If that first person had not blocked the lane, the people behind him would have proceeded on up the road, leaving the lanes available for those behind them to use. Same for the second person blocking the lane, and each after them.

Lane blocking not only creates jams, but prolongs them as well when someone at the head of the jam continues to block the left lane instead of moving right and allowing those behind to move forward and get out of the way of those behind them.

If you’re sitting in this traffic at the back of the jam, it’s hard to believe that something so simple as lane discipline can work. Consider, though, that most of the cars around you wouldn’t be here now if the cars in front of them were further down the road instead of blocking them, and on and on up to the left lane blockers at the very front.

In front of this jam, just a few miles ahead of you, are miles and miles of I-94 with much lighter traffic—a lot of excess capacity. But a few people are preventing others from using this excess capacity.

In Europe, where Lane Discipline is routine, you don’t see the weaving, tailgating, and road rage to the extent we have here in the U.S. Their highways are more efficient, people drive faster and at more consistent speeds, and yet they have fewer fatalities and many fewer crashes. Their law enforcement knows the importance of keeping the lanes open for traffic flow and are much quicker to ticket someone for blocking a lane (left or middle) than speeding.

In the U.S., some western states have enforced lane discipline for years and recently Texas began doing so and New Jersey recently began heavier enforcement and increased fines for blocking the left lane.

Minnesota already has a law (169.18(10)) requiring slower vehicles, regardless of their speed or the speed limit, to move right, we just need to begin enforcing it. Many people think that this applies only to vehicles moving slower than the speed limit, but that is not the case and may be the crux of the problem.

Perhaps more important, people need to understand why we have that law and why it’s being enforced. They need to understand that blocking the left lane isn’t just against the law, but that their blocking the lane makes our roadways significantly more dangerous for everyone and needlessly causes a traffic jam.

Another way to think of it is this—Mind The Gap–if the car behind you is closer than the car in front of you, you likely need to move right and let others utilize the space in the gap in front of you.

Tailgating is dangerous. Enraging other drivers is dangerous. Weaving in and out of traffic is dangerous. Inconsistent speeds in the same lane is dangerous. Passing on the right is dangerous. And we effectively encourage all of this by not enforcing lane discipline—Keep Right Except To Pass.

We likely have enough road surface, we just need to use it more safely and efficiently. We have nothing to lose and potentially much to gain by enforcing some lane courtesy. If traffic continues to be a significant problem, then we can consider spending millions for extra lanes.

The next time you’re stuck in a “phantom” traffic jam, MITs term for those jams that you get to the front of only to find nothing there to have obviously caused it, consider this; You are likely in this jam thanks to a lane blocker or two. If people five, ten, or thirty minutes ago hadn’t blocked the left lane, the people in front of you would be further down the road right now instead of sitting in front of you.


Walker Angell

About Walker Angell

Walker Angell is a writer who focuses mostly on social and cultural comparisons of the U.S. and Europe. He occasionally blogs at localmile.org, a blog focused on everyday bicycling and local infrastructure for people who don’t have a chamois in their shorts. And on twitter @LocalMileMN