What is Car Platooning? Highway Hookups Explained

There’s lots of hype around self-driving cars, but what gripes my gears is that nobody seems to be talking about what I think could be the biggest benefit: platooning.

That’s when cars connect electronically and travel in groups, like a small train. Imagine zipping through a construction zone or busy on-ramp as the cars talk to each other, driving with precision – and safety– in a way that’s impossible for human operators.

How many times have you been trapped in the accordion effect on the highway? That’s when a driver a mile ahead of you taps their brakes briefly to avoid crashing into some fool changing lanes in front of them. That sends a shock wave back through the line of traffic. Sometimes you come to a complete stop without ever knowing why.

Watch what happens when the line of traffic starts moving: every car and truck accelerates at a different pace. The same thing happens at a traffic light. The cars roll out at different speeds, based on the attentiveness and skill of the driver. Think of how many more cars we could put on the highway if each car kept the same distance between it and the next car?

Consider construction zones where two lanes squeeze down to one lane. Our sense of fairness says we should try to move into the open lane as far ahead of the restriction as we can. We get mad at those inconsiderate dopes who zoom past us and dive into the open lane at the last possible second. Well, research has shown that the zipper merge, as it’s known, is actually the most efficient way to do merge lanes. Cars that communicate with each other could turn the zipper merge into a thing of beauty, like a well-trained marching band just barely missing a collision in the trombone section.

Now, I don’t want 100-mph car trains. I’d be happy with 20-30 mph car trains through construction zones and congested areas. Research shows the best gap between cars is about 20-feet. That allows for small variations in distance without starting the accordion effect. Lower speeds would be safer for passengers in case of an emergency. Picture your car hitting a panic stop at 75 mph. Not good at all.

Research shows Los Angeles residents waste more time in traffic congestion than other drivers on the planet, on average 102 hours every year. The second worst city is New York, with 91 hours wasted, and followed by San Francisco with drivers there losing 79 hours to congestion.

Think how much pollution we could cut by keeping traffic moving. If those cars are all electric vehicles, the pollution issue goes away. But think about the increased productivity and reduced potential for road rage by putting computers in charge of your morning commute.

More roads aren’t the answer. We can’t build ourselves out of traffic congestion. If we add more lanes to a highway, they eventually fill up with cars again. With platooning, we can reduce congestion within our existing infrastructure.

Volvo has demonstrated platooning on normal roads with three cars driven autonomously behind a lead truck moving at speeds up to 55 mph (90 kph) with a gap of no more than 20-feet (6-meters). This system is called SARTRE (Safer Road Trains for the Environment). The vehicle at the very front of the platoon controlled the speed. The following cars then snapped together in a single-file line behind the first vehicle and drove themselves safely at close proximity on the highway.

The Volvo test limited platoons to 10 vehicles so platoons and ordinary traffic could intermix, without having to worry about blocked freeway exits.

The U.S. Army conducted a car platooning proof-of-concept using five Cadillacs with automated longitudinal control at Aberdeen Proving Ground in Maryland. The vehicles were fitted with a special computer and vehicle-to-vehicle (V2V) communications devices.

The computers inside the vehicles not only control braking and accelerating, but use radar data from the front vehicle that’s part of the production adaptive cruise control system to create a cooperative adaptive cruise control capability. The cars could see where the car in front of them was located and how fast it was going, then control the brakes and throttle, and therefore control the position of the following vehicles.

Platooning is possible, or will be soon. Most new cars come equipped with enough communication gear and sensors to make it a reality, such as Bluetooth and wireless, GPS, and radar-sensing systems, as well as drive-by-wire steering and throttle controls.

So when will we see platooning cars? Maybe never. There’s a lot to work out before our cars start hooking upon the highway.

Despite the complexity, the technology is relatively easy. However, the legal and social hurdles are higher. Perhaps platoon lanes could replace the high occupancy vehicle lanes in some cities. The cars would need a system to engage and disengage from the platoon, and alert the drivers to what’s going on. I’m sure someone will develop an app for that as well. And of course, drivers would still have to pay attention.

So the biggest barrier to better motoring just might be ourselves. That’s always been the case. But a guy can dream, can’t he?


Driving Tests – https://www.drivingtests.co.nz/resources/what-is-vehicle-platooning/

U.S. Department of Transportation – https://www.volpe.dot.gov/news/how-automated-car-platoon-works

Minnesota Department of Transportation – https://www.dot.state.mn.us/zippermerge/

MIT – http://news.mit.edu/2016/driverless-truck-platoons-save-time-fuel-1221

Forbes – https://www.forbes.com/sites/niallmccarthy/2018/02/08/the-cities-where-u-s-drivers-spend-the-most-time-stuck-in-traffic-infographic/#51cf387716d8

Volvo – https://www.media.volvocars.com/global/en-gb/media/pressreleases/45734

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