What say this group on the virtues of drafting trucks? Most commercial 18 wheelers are governed at 100 kilometers per hour or less now days, and I have found that if I get behind one and stay 1 or 2 car lengths behind, I have a significant mpg gain.

I know the truck driver can't see me, and I can't see what is going on ahead of the truck, but if I concentrate on the trucks brake lights, I seem to stay out of trouble.

Is what I'm doing OK, or is it just tacky and poor road etiquette?

 

Sorry, OE, my response is NO, NEVER, PLEASE DON'T DO THIS....a few mpg's are not worth the risk.... one mistake, one blown tire you could be gone. A second or two at highway speeds is not very much.....next time you are out driving find a fixed object on the side of the road, pace it by counting 1001, 1002, how much space has passed, how fast can you react & stop/avoid that big object in front of you?

 

I would have to agree that it's not worth the risk. Even if you can stop quicker than the 18 wheeler, all it takes is a half a second and you'd be in the back of his truck. I used to drive that way, but actually found that by taking my time and not driving aggressively, I'm much more relaxed and have less stress when i'm on the road. Surprisingly, most drivers either will pass me (to which, I am next to or behind them at the red light) or just stay behind me and go at my speed (typically within 5 mph of the speed limit).

Regardless, for your own safety and that of the others on the road, don't draft or tailgate the big trucks (or anyone else for that matter!).

 

For many hypermilers it's quite simple really...

Close drafting- Absolute NO NO.
Surf drafting- OK, with some caution
Distant drafting- OK, with some caution

However, for me no kind of drafting is worth the stone chips I get even when riding a distant draft of a truck. On some roads, those little tiny rocks remain bouncing many seconds after the truck passes and they still do a number on the front bumper and hood.

Cheers;

MSantos

 

When I do it, I seem to settle in about 40-50 feet back. Enough that some onramp jockeys will always seem to want power in between me and the truck on their way to the inside lame.

Now assuming you are going at 100 kilometers per hour, 40-50 feet would in a worst case situation provide about .005 seconds to take evasive actions(in the unlikely case that the truck was to completely stop). In reality, an event that requires evasion will give you at least .5 to 1 second to respond.

Most (but not all) automobile/truck rear-end collisions are due to operator inattention. I must say that when I do attempt drafting, While I am always concentrating when I drive, I am in a much higher state of concentration When drafting then when I am just driving down the road. I also periodically go out of formation to read the road conditions ahead, and try to model the level of risk.

If I was to recommend drafting, I would only advocate it on large multilane highway with center divide barriers, a moderate traffic load, and minimal or no congestion and at speeds no higher than 100 kilometers per hour.

On the issue of colliding with debris from a truck tire disintegration, While this is a concern, I have to say that this event provides a significantly high precursor warning and can be more easily avoided. Again concentration is key. I have been involved in about 10 tire disintegrations at speed in my driving life, and have seen from these experiences that they usually do not just happen, they take time to happen, which gives you more time for evasive actions.

Road debris collisions are a significant issue (such as a shredded tire tread on the road, but when drafting, this is somewhat mitigated by the truck driver's actions of not wanting to hit what is in the road. They having a better view of the road ahead and will usually take timely evasive actions that can be read by the drafter. Another reason that concentration and reading the trucks actions are key.

The hard collision events are oncoming objects in your path(such as tires, golf *****, other cars or trucks, livestock, etc.) In those situations having a large object in front of you may be better than not having anything at all.

 

Odds of an accident are pretty low, but this is one of those risk-reward trade-offs where I just can't accept it.

For non-distracted driving, you're looking at .4 seconds to react. If the truck hits its brakes and drops 20mph before you react, you'll be roughly 5 feet closer. If you were two or three car lengths back, you're fine. Not even sweating.

Now say you were glancing in your review mirror, chatting on the cell phone, or simply over 65. Now your reaction time would drop anywhere from .3 to 1 second later. Instead of 5 feet closer, you're somewhere between 15 and 45 feet closer. You could easily find your car hitting the rear of that semi if you were keeping 4 car lengths.

Again, how often would it happen? Rarely, probably never. But what is the value of the gas gained vs. value of the life lost?

 

The expression that comes to mind is

If you have to ask.............. You probably already know the answer.

 

I'll admit that I do it, but not all the time, generally when traffic is a bit lighter. I'd say on an average of 3-4 car lengths behind, only on multi-lane freeways between Sac and SF (80 and 680). I always try to leave space for an out.

 

My approach is (1) only distance drafting (>~60ft) and (2) only at higher speeds, like 65mph. But the hardest part is actually finding a truck going around the right speed & steady/predictable.

 

I draft semi trucks but only at a distance of 75 to 100 feet back. This distance is safe for me and it does provide a small but measurable increase in mpg. The episode of myth busters tested and confirmed this. Their test was done at 55 mph and the figures were as follows..... * 55mph control: 32mpg
* 100ft: 35.5mpg, 11% improvement
* 50ft: 38.5mpg, 20%
* 20ft: 40.5mpg, 27%
* 10ft: 44.5mpg, 39%
* 2ft: 41mpg, 29%

The fuel economy actually dropped at 2ft. Andrew Smith's theory was that at 2ft, Grant got nervous with the throttle as it was difficult to maintain that 2ft gap.
Clearly anything closer than 50ft is stupid, and never worth it, but if im cruising down the interstate and i have to choose a lane by myself or a safe distance behind a semi, i slide in behind but not overly close and reap every small increase in mpg, even if its only 10% to 15% at that distance. Every little bit helps as long as your not too close.