Drafting at Highway speed..It works

[DFibRL8R]

I can see myself doing it between St Augustine and Savannah for sure, the rest of the time it really is not important.

I followed a large truck at 2-3 seconds following distance (pretty typical following distance) in my 60kWh between Savannah and St Augustine on a cold drizzly January day (temps 34-42 F)and it helped me avoid having to stop in between for some slow charging (I had scoped out possible options just in case). Averaged 66mph, 286Wh/mile and arrived with 22 miles Rated Range left.

 

[jcaspar]

It only helps the drivers not paying attention. I suspect an attentive driver would be much safer as they can see situations ahead (stopped cars ahead) and could anticipate slowing down long before the radar would see the car in front slowing.

I imagine radar cruise control automatically solves this?

 

[GreenT]

Guys, let's discuss the merits and perils whilst avoiding belittling each other.

What's belittling about being candid.
These "adults" are sending the WRONG message and encouraging very dangerous driving.

 

[MikeL]

Elaborate on the underlined, please. Thanks.

Several ways the driver could say "No Thanks"
slow way down
put his right side tires over the line - assuming you're both in the slow lane - that would have the added 'information' of extra airborne rocks
He could signal you with his lights/flashers/turn indicators

just so you guys know, I picture this event happening out on the open interstates of NV and WY where cars are often literally miles apart. NOT in ANY urban-ish highway setting where constant changes in situation are to be expected. A big rig and me close together between Filmore and Meadow on I-15 would not be a problem. I am a safe driver, just wanted to say that IF you want to draft a truck, let him know you're there. He might help out, or not.

 

[Chipper]

I think the term "drafting" is not a good one since it conjures up visions of Nascar drivers literally on top of one another. I do believe there is a safe distance to follow a larger vehicle which can still improve range. On a busy highway, you're going to be behind somebody, why not improve your range by following behind a larger vehicle at a safe distance? Clearly 1.5 to 2 car lengths is pushing it at high speeds. I prefer the "2 second rule". Stone chips, tire debris and limited view of stray tow hitches/potholes in the road are the main hazards but I'm fairly confident I can stop my model S with Brembo's in much less distance than the guy driving the 18-wheeler can. The Model S tests 60 to 0 in 108 ft. Unles you're not paying attention or you are ridiculously close, you are not going to rear-end a semi.
Two-second rule - Wikipedia, the free encyclopedia

It is not the braking I would be concerned about. It would be the blown out tire, the trailer hitch, the leaf spring blade, the builder's ladder. The 18 wheeler can clear all of these with no issue. My Tesla OTOH cannot. The truck scoots right along over it and I don't care how fast your reflexes, you cannot avoid something of that nature. Oops! Honey where is that Tesla Road Service number???

 

[Al Sherman]

There's been a lot of arguing back and forth on this "issue" as far back as the Prius Chat days. I've never commented and am not judgmental about it either way. I WILL admit to having tried it in both the Prius and the MS just to see if it works and it clearly does.
I've flown supersonic fighters in fingertip formation. The truck drafting felt very dangerous to me.

 

[jerry33]

The truck drafting felt very dangerous to me.

No kidding.

 

[dsm363]

You still get a decent benefit if you stay back far enough to see the trucker's side mirror. One car length is very dangerous and will anger many truck drivers as they can't see you back there anymore. If you do rear end them somehow that accident still impacts the trucker even if it isn't his or her fault (likely lost income from having to miss hours or a day of driving to stick around and talk with police or loss of the use of their trailer, lots of paperwork I bet, accident on their work record and damage to company property). Also, if accident is severe enough you can shut down one direction of traffic on a highway for hours. Let alone cause an accident in traffic the other direction from rubbernecking.

 

[green1]

It only helps the drivers not paying attention. I suspect an attentive driver would be much safer as they can see situations ahead (stopped cars ahead) and could anticipate slowing down long before the radar would see the car in front slowing.

You can't see a thing ahead when you're behind a big truck or bus at that distance, and the Radar has a much better reaction time than you do.

Sure you can stop quicker than the truck can if he's using his brakes, but that means you're assuming that he's not going to be your problem. There's no guarantee the radar will save you. Here are some easy examples of places where you get in big trouble real quick:
- tire blows out on truck
- truck runs over something that he has the clearance for but you don't
- something falls off truck
- truck crashes
- a vehicle is at a full stop in your lane, you can't see him because of the truck, truck chooses to change lanes instead of braking, he does it last minute, you can't change lanes because someone is beside you. (good luck slowing to a stop from highway speed in the length of the truck)

There are two ways of safely drafting:
- don't
- or stay 3 seconds back (you'll get some benefit, though not nearly as much)

I've seen the aftermath of following a truck too closely. It's just not worth it.

 

[brianman]

You can't see a thing ahead when you're behind a big truck or bus at that distance

You need to be more specific when making such assertions. Since you didn't specify, I'm assuming 20 cars lengths and thus your assertion is completely incorrect.

 

[green1]

The conversation was about 1-2 car lengths. I shouldn't need to specify it again in each reply.

 

[jerry33]

You need to be more specific when making such assertions. Since you didn't specify, I'm assuming 20 cars lengths and thus your assertion is completely incorrect.

No offense here, but "car lengths" is about the silliest measurement I can imagine (well, maybe bubblegum bubble diameter might be even sillier). A Tesla car length is 3x what a Smart car length is. I can understand seconds--works for everything, and everyone who has a drivers license can count to five (overkill since they only need to count to four). I can understand metres, although I wouldn't bet my life on being able to correctly estimate 30 meters (as opposed to 25 or 35) but there is no way I can estimate 20 car lengths.

There is an episode of Dragnet where Sgt. Friday is explaining how simple it is to calculate car lengths (couldn't find it on youtube), but it's hilarious. No one would do that in real life.

 

[brianman]

No offense here, but "car lengths" is about the silliest measurement I can imagine

Wasn't my measurement. That's always what they used in Driver's Ed. Fix the schools rather than blaming the students.

- - - Updated - - -

There is an episode of Dragnet where Sgt. Friday is explaining how simple it is to calculate car lengths (couldn't find it on youtube), but it's hilarious. No one would do that in real life.

Not the one you were looking for but interesting and somewhat on-topic:
Warning: May be a bit strong for children.

- - - Updated - - -

@jerry33 - Maybe in this one?
Dragnet - The Big Hit And Run Killer - Free Old TV Shows Full Episodes - YouTube

 

[jerry33]

Wasn't my measurement. That's always what they used in Driver's Ed. Fix the schools rather than blaming the students.

I had thought they stopped teaching car lengths twenty years ago

 

[FlasherZ]

We were taught in terms of seconds. Watch a car pass a fixed object, start counting. Suggestion was to maintain 3 seconds.

 

[rpo]

I have been drafting behind semi trucks in my Prius for the last five years. At 4-5 car lengths, I can consistently get 75+ MPG on 100+ mile road trips at 65 MPH. On a few out-and-back road trips, I managed to get nearly 100 MPG both ways. So.....drafting does work. Nearly any car will stop faster than a big truck, so as long as the truck ahead of you hits the brakes in time to avoid an accident, so should you. Now if you are being distracted while driving, DON'T DRAFT.

 

[brianman]

I had thought they stopped teaching car lengths twenty years ago

I think you just called me on old geezer.

Get off my lawn!

- - - Updated - - -

We were taught in terms of seconds. Watch a car pass a fixed object, start counting. Suggestion was to maintain 3 seconds.

This was taught "in my day" as well, but car lengths too.

 

[Bigbit]

I think the term "drafting" is not a good one since it conjures up visions of Nascar drivers literally on top of one another. I do believe there is a safe distance to follow a larger vehicle which can still improve range. On a busy highway, you're going to be behind somebody, why not improve your range by following behind a larger vehicle at a safe distance? Clearly 1.5 to 2 car lengths is pushing it at high speeds. I prefer the "2 second rule". Stone chips, tire debris and limited view of stray tow hitches/potholes in the road are the main hazards but I'm fairly confident I can stop my model S with Brembo's in much less distance than the guy driving the 18-wheeler can. The Model S tests 60 to 0 in 108 ft. Unles you're not paying attention or you are ridiculously close, you are not going to rear-end a semi.
Two-second rule - Wikipedia, the free encyclopedia
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Well, you do know that your reaction will come after the rigs reaction. So you will react after the brake lights come on. Good luck with that!! You will have hit him before your foot reaches your brake pedal... At full speed minus a bit of regen that is....

 

[Rebel44]

Well, you do know that your reaction will come after the rigs reaction. So you will react after the brake lights come on. Good luck with that!! You will have hit him before your foot reaches your brake pedal... At full speed minus a bit of regen that is....

Not really - being 2 seconds behind that rig at 90 kph means that you are 50 meters behind him. Considering that distance + fact that 18-wheeler have much longer stopping distance compared to normal car, you shouldnt have a problem breaking behind him and/or changing lane.

View attachment 52510

 

[Bigbit]

Not really - being 2 seconds behind that rig at 90 kph means that you are 50 meters behind him. Considering that distance + fact that 18-wheeler have much longer stopping distance compared to normal car, you shouldnt have a problem breaking behind him and/or changing lane.

View attachment 52510

I was referring to the 1-2 car length drafting. At 50 meters that is 9-10 car length. I see no problem with the latter...