Around the Tennessee Valley we have no doubt all experienced the 'phantom' traffic jam. You're driving along just fine until all of a sudden you're in stand still traffic for no rhyme or reason. It turns out that reason could be as simple as someone who tapped the brakes because they were looking at their phone and not the road. Or somebody decided they just had to slow down to see a fender bender wreck on the side of the road. Whatever the reason, it's something small that can end up affecting traffic for miles by creating a traffic wave. Most phantom traffic jams are caused by drivers overcorrecting with their braking. The wave starts out as people lightly hitting their brakes at Mile Marker 1 but by Mile Marker 3 cars are slamming on brakes and creeping along at 5mph.
The above video shows you exactly how a phantom traffic jam is caused while the below video informs you on how we can do our part to cut down on them.
Ways to help stop phantom traffic jams:
- Use the Zipper Merge
- There are many areas in the Tennessee Valley that go from 2 lanes to 1(whether that be the natural flow of the road or construction zones). While the majority of drivers will get in the main through lane well ahead of the merge, the suggested (and most traffic efficient way) is to zipper merge. This is a simple merge where the ending lane vehicles merge evenly into the main through lane as their lane ends, not earlier which can lead to brake checks as cars try to get over early. Yes, the person who bypassed 40 cars to cut in at the front of the line was actually helping traffic.
- Don't Weave in traffic
- Instead of saving time by weaving in and out of slower drivers, don't. Studies have found that you will only save 1-2 minutes during an hour plus drive but dramatically increase your chance of a wreck. This also leads to brakes checks which can cause a traffic wave.
- Stop tailgating and use bilateral control instead
- A big problem for many drivers is riding the car in front's bumper. This is not only dangerous but a big contributor to phantom traffic jams as it leads to more brake checks which create the traffic wave effect for the vehicles behind you. Instead use bilateral control. Try to keep an even spacing between the car in front of you, as well as the other cars around you. This will allow more time to slow instead of forcing you to stand on the brakes because the car you were tailgating decided to brake all of a sudden.
- Use Adaptive Cruise Control (ACC)
- Many new vehicles now have adaptive cruise control. Instead of just going 70mph, ACC has sensors to adjust your speed to match the vehicle(s) in front of you. This allows for a smoother flow of traffic without having to constantly adjust your speed while also helping you resume speed more smoothly. The more uniform speed all cars travel, the less chance of a phantom traffic jam. Researchers found that using a fleet of 36 vehicles with ACC on a test track, the last car only had to reduce its speed by 5mph to accommodate the vehicles suddenly braking in front of it. In fact, they found only 1/3rd of the cars needed to have ACC to have similar results.
The main takeaway? Our bad driving is the reason Phantom Traffic Jams exist. Try to maintain as constant a speed as possible while being as predictable as possible. Traffic works best when it flows at a continuous pace, don't be the log jam that messes that up!