Auto Drafting Mode to Save Energy

[ItsNotAboutTheMoney]

I used to remember closely following tractor trailer trucks to maximize fuel economy back in the ICE days, and a though occurred to me that with the right software tweaks, our Tesla Model S/X autopilot be can really good at this.

It was reported that by closely following a truck, one can save 10% energy at 100ft, maybe 40% energy at 10ft when moving at say 90km/h (55mph). Hey, Mythbusted did it, so it must be true right?

Want to Save Gas? Follow That Truck!
MythBusters (2007 season) - Wikipedia

Now, 100 ft is really too close for comfort at highway speeds and 10ft is blatantly unsafe. However, given that a Mode S/X can brake harder than a truck and autopilot reaction time can be a lot better than human, there may exist an auto-draft mode that would follow a large truck at say 50ft and allow the following vehicle to save 20-25% energy, pretty significant. 50ft is about 0.5s at 60mph/100km/h, probably well within reason for autopilot reaction time.

Imagine, instead of 200wh/km we would do 150wh/km going at the same speed.

I wish people would give up on this kind of idea. Instead of compressing distances we really want to _increase_ distances to reduce collisions and their severity. Each highway collision kills, injures, and cause a lot of additional energy use. Not to mention the wasted time that hurts economic productivity and quality of life.

Safety first.

 

[artsci]

I wish people would give up on this kind of idea. Instead of compressing distances we really want to _increase_ distances to reduce collisions and their severity. Each highway collision kills, injures, and cause a lot of additional energy use. Not to mention the wasted time that hurts economic productivity and quality of life.

Safety first.

One can draft successfully while maintaining a safe distance behind. No need for tailgating.

 

[DarkMatter]

There is an energy consumption difference even at safe distance - which is when you can see both of the truck mirrors at once. Any closer than that, and you'd best be getting ready to pass.

 

[Austral]

Drafting is tailgating. NASCAR tactics do not belong on the street. Love breaking rules (and track time) but not looking to kill anyone with a 5,000-lb vehicle.

For a robot to successfully do it safely, there will need to be knowledge of the other vehicle weights, brake component wear of other vehicles and yours, condition of tires & road surface, a willingness to accidentally bump the car in front, and so on. That doesn't sound feasible. Safe distance is required.

 

[ecarfan]

On the highways I drive (meaning the Western US) a significant fraction of all drivers tailgate cars that are traveling at or over the speed limit, meaning they do not maintain a safe distance between themselves and the car ahead of them. When I observe a car tailgating me I either move to the right to let them pass (if possible) or I gradually slow down enough so that they decide to go around me on the left. The risks many drivers regularly take at high speed continue to amaze me. They think they are superhuman and nothing unexpected will ever happen.

TACC set at "1 or 2" in my opinion definitely does not provide adequate distance because TACC is not yet perfect and human attention and reactions times are inadequate, and I am disappointed that Tesla allows such a setting. I keep TACC at 7 and wish there was an "8".

Regarding the OP, yes someday it may be possible for AP to allow what is described when traveling in a row with other AP cars. But that is many years away.

 

[AmpedRealtor]

Using Autopilot or not, this is a great way to get a ticket. I hope anyone who does this gets pulled over and cited.

 

[Triptych]

I am not saying drafting or closely following is safe as it exist today. There are many variables involved but human reaction time is the most significant factor as the actual braking distance apply to both the car you are drafting and you, making it a relatively non factor. What I am suggesting is that as driver assistant technologies improve, there would be a day (maybe we are closer to it than we think) that close following can be done safely. When that happens, vehicles should have a mode that allows them to closely follow, improving the energy efficiency of all cars involved.

We bulk at the concept specifically because it is deemed as unsafe. But what if near instant reaction time and near flawless detection capabilities makes that possible? Train cars follow each other very closely, and we are OK with that because we believe the mechanical linkage allows near instant reaction time and detection (obviously), so if cars can do that too due to improved automation capability, then why not?

I picture an all-Tesla paceline of sorts. Peloton Mode? Vehicle-to-vehicle communication controls a line of vehicles where each car leads the pack for a few minutes then drops to the back. No semi involved, unless it's a Tesla semi.

Are you a cyclist perchance?

 

[Austral]

Cyclist? I am. Been in some rough crashes. For cars, not worth the risk above 30 mph. Also serves no purpose to have vehicles in a tactical bumper lock at highway speed unless some of us do personal security details for world leaders. Vehicles communicating with each other would still not be able to accurately guess the effects of part wear on brake performance, but again the key question is why do it at all? It's sounds like some random act inspired by an unrealistic B-movie called F8.

 

[DarkMatter]

Systems could totally understand part wear. Machines do it all the time. The robots that built your Tesla keep track of it so that they can keep working.

Auto-draft is still a bad idea, though. After we have lots of autonomous vehicles, sure. Not now.

 

[bhzmark]

Drafting is only advisable when your think you'll be short of range to reach the next supercharger or other charging source. I've done that a few times and it's saved me in those situatiions. And as @Reciprocty notes, you don't need to draft a semi. A large van or SUV serves the purpose quite well.

Exactly.

my driving now is way more conservative and safe then it was before EV/Autopilot. I find that AP allows me to scan farther ahead and be more ready for issues and not trying to pass every car is making me a safer driver and able to focus more on what is directly in front of me instead of checking my blind spot to pass every car.

+1

Instead of compressing distances we really want to _increase_ distances to reduce collisions and their severity.

Exactly wrong. Increasing density increases traffic flow and volume reducing commute times and congestion. This will eventually be done safely with v2v and autonomous driving.

Vehicle-to-vehicle communication controls a line of vehicles

Right . Cars will eventually become like train cars -- one right behind the other.

 

[ItsNotAboutTheMoney]

Exactly wrong. Increasing density increases traffic flow and volume reducing commute times and congestion. This will eventually be done safely with v2v and autonomous driving.

If there are large numbers of autonomous vehicles we'd expect lower traffic volume due to increased ride sharing, so we wouldn't need to increase density. That would create a system that works better with the initial mixture of autonomous and non-autonomous vehicles, and it would be more tolerant of failure.

Right . Cars will eventually become like train cars -- one right behind the other.

Train cars are connected together and powered by a separate engine.

 

[ecarfan]

Cars will eventually become like train cars -- one right behind the other.

The key word being "eventually". We are many years away from such a scenario.

For now, drafting is dangerous. Following another vehicle at a distance that is not safe endangers the driver who is drafter and those around that driver. Despite what one may think, we do not have superhuman reflexes or X-ray vision or an ability to predict the future. And TACC is not reliable enough to make drafting safe.

 

[S4WRXTTCS]

I think some of you are confusing the idea of staying behind a large vehicle for efficiency gains with drafting.

With drafting you are really too close, and it is illegal. Hopefully at some point we will have car-car communication enabled drafting mode. Where a bunch of cars could get together to choose to engage in it. Where the front car communicated to the other cars about what was ahead, and the drafting mode could easily be undone. Where they could occasionally trade of on the leader. With a Tesla it's kinda funny because we know we're likely headed for the same supercharger so why not?

But, until then the only option we really have for efficiency gains is to stay behind a large vehicle. There is no ap setting that will get me pulled over by a cop for following too close. If everyone used similar adaptive cruise control systems the roads would be safer and we wouldn't have so many tailgating caused accidents.

There is nothing wrong with simply choosing to stay behind a large vehicle. Sure there is a trade off, but if you're trying to conserve those trade offs are worth it. You accept less warning if there is a pot hole or some debris on the road. Like others have said a semi is likely not your best choice. Last time I picked a moving van to stay a safe AP set distance behind. I am the one driving so of course I was also paying attention. I don't use AP to reduce my attention. I mostly use TACC to keep a consistent speed and I wish other motorist would use adaptive cruise control systems. I'm tired of people who driving 70 one moment, 80 the next, and 60 a few moments later with no change in the speed limit.

 

[S4WRXTTCS]

The key word being "eventually". We are many years away from such a scenario.

For now, drafting is dangerous. Following another vehicle at a distance that is not safe endangers the driver who is drafter and those around that driver. Despite what one may think, we do not have superhuman reflexes or X-ray vision or an ability to predict the future. And TACC is not reliable enough to make drafting safe.

I think it's kinda of ironic that a person from California is talking about how drafting is dangerous. I don't disagree at all, but this is HOW YOU GUYS DRIVE.

The people from California do drive as if you have super human reflexes. Either that or you guys really enjoy sniffing other peoples fumes. Chances are if someone is on my butt they are from California. We're talking about so close they could be in violation of the human three foot rule let alone the safe following distances rules.

Now I don't mind your stopping rules. But, geesh you guys get too close.

 

[EVie'sDad]

Agreed, any larger vehicle will do, as for drafting programs, we all ready have one! AP set at 1 or 2 provides plenty of spacing. Pay attention and you should be ok

Warning! Any setting of distance below 5 at highway speeds is taking your life into your own hands, the Tesla will be unable to avoid collision with any vehicle in it's path at that distance. Even it cannot react fast enough to stop. I would not risk the lives of me or my family or friends on the chance that the car may be able to brake in time.

 

[kort677]

Warning! Any setting of distance below 5 at highway speeds is taking your life into your own hands, the Tesla will be unable to avoid collision with any vehicle in it's path at that distance. Even it cannot react fast enough to stop. I would not risk the lives of me or my family or friends on the chance that the car may be able to brake in time.

nonsense! I've drafted trucks for 50 miles at a time with it set on 2. you've offered a blanket one size fits all statement that just isn't true.

 

[number12]

Replace a $1500 X windshield and see how much you try to be behind trucks. I avoid like the plague.

 

[tga]

Ever see a tractor blow a retread? Do you really think it's wise to be 50 feet behind it? Or even 100 ft?

+1000!!

Not too long ago, I was a less than a 1/4 mile behind a tractor trailer when it had a blowout and flung its tread. It went high enough I lost sight of it above my windshield, and the next thing I know it was raining tire chunks in front of me.

You definitely don't want to be near a truck when one of those lets go.