Shockwave Jam

During a couple of days spent driving to visit family over the Thanksgiving holiday, I experienced a phenomenon that I’m sure is familiar to most of you: An interstate highway traffic jam with no apparent cause. After cruising along smoothly in moderate traffic for miles, I would crest a hill or round a bend and suddenly be faced with a sea of brake-light red threading its way far into the distance. I used to think bumper-to-bumper standstills like this were caused by an accident up ahead, but often, as was the case here, when traffic starts moving again, there is no evidence of an accident or anything else that might have caused the backup.

The phenomenon, I learned several years ago from Tom Vanderbilt’s book, Traffic, is called a “shockwave jam.” It’s a chain reaction that can be caused by a single driver slowing down, changing lanes, or even just tapping on the brakes.

We’ve all experienced this wave in reverse while waiting in a long line of cars at a traffic light. When the light changes, only the first car has room to move forward. A beat later, the second car starts to move forward, but all the other cars are still stopped. This “wave” of motion slowly moves through the line of cars until the light changes back, infuriating any drivers who never made it through the intersection.

The wave has the opposite effect on the interstate. Even with restricted access, no stop lights, and 65 mph speed limits, traffic not only slows down but often comes to a complete standstill simply because, for example, someone changed lanes. That causes the driver they pulled in front of to tap the brakes, which causes a chain reaction as all of the cars behind, one by one, tap the brakes. Even if each car slows down just a little, eventually the whole line of cars slows to the point that the next car in the wave must actually stop, as must the car behind, and the next car behind, and so on. 

Part of the problem is that cars are too close together. (Way too close together, in fact. According to the “three-second rule,” cars moving at 65 mph—a travel rate of 96 feet per second—should maintain a spacing of … wait for it … 19 car lengths or 288 feet.) With more space between cars, a slight slowing of one would decrease the spacing but not necessarily cause the following car to slow at all.

There are other issues, of course—inattentive drivers, speeders, joy-riders, etc.—but even in a highway occupied only by model drivers, one problem remains: Lack of communication. No one knows what other drivers are going to do, or when and why they are about to do it.

One solution is autonomous vehicles. Whether on the highway or downtown, when every vehicle is communicating its location, speed, and travel route to every other vehicle, shockwave traffic jams would be a thing of the past.

Unjamming Remodeling 

It remains to be seen whether autonomous cars solve more problems than they cause. But the root cause of the shockwave jam may also explain why many, if not most, remodeling companies miss their deadlines. Like highway drivers who don’t leave enough “following distance,” remodelers who don’t allow enough time for the effects of unknowns are vulnerable to a scheduling pileup. 

Unknowns are myriad: an error on the plans; an incomplete, damaged, or incorrect delivery; a failed inspection; a no-show trade contractor; a jobsite injury; a meddling homeowner. Like a driver tapping the brakes or switching lanes, almost any delay or change early in the process ripples through the whole project. And these days, the problem is exacerbated by increased reliance on subcontractors, all of whom have their own shockwave jam of backlog projects and service work to attend to.

Lack of communication is also the root cause of the remodeling shockwave. Autonomous vehicles are already on our roads, but your company will never run itself. Systems are essential, but they still need people to monitor them and make adjustments. In a world where streamlining the sales cycle, and reducing or eliminating delays and punchlists are increasingly important, unless you are constantly communicating with your team, your vendors, and your subs, one day you’ll come around the bend to find your project calendar backed up for miles, bumper-to-bumper.