To draft or slow down?

[GasSavers_RoadWarrior]

Something I notice with driving Wile-E more again is an effect around the 55-65mph mark which is just before a laminar to turbulent flow transition point, which can mean a drop in the effective Cd, before the cube of the speed rule takes over again. The effect is that "messy" vehicles, leaving a very turbulent wake, no matter how large, provoke early laminar to turbulent flow transition when you follow them. This feels like it drops aero drag in a small speed range dependant on aerodynamics of your car, just below the laminar/turbulent flow transition. This effect also seems to persist further behind the vehicle than the conventional "draft" or "tow". The effect is further up the speed range with lower Cds and shorter vehicles. I think I discussed in another thread about the lam to turb transition "notch".

So you might say, just provoke the turbulence yourself! Well it's not that simple, the gain is only seen in a narrow speed range, below and above that, due to various other effects, the turbulence makes more drag, unless you either have active turbulation devices that only operate in that speed range (specific to vehicle don't forget) or place them at the very rear of the vehicle, where in the low speed range, surface drag and skin friction is minimised, and at higher speeds they do not cause a "snowballing" of turbulence along the vehicle, but they only reduce base drag and can change form (shape) drag.

Anyway, turbulent air, in a narrow speed range should increase FE slightly. "Drafting" a harley is sort of possible. Prius and Insight drivers will probably find this speed range is higher than legal speeds most places.

[KU40]

[QUOTE=diver1972;118615]

While some may cry out "But you're being a rude bastard by doing this!", to them I retort "But it was the other driver who was first rude by being inconsiderate and/or unaware of those drivers around him/her."

QUOTE]

I have a question about this. It's not directly in line with what has been said, I just want to get viewpoints on it. The situation: I'm in the right lane, doing 70. I'm coming up on a vehicle going 65 in the right lane, that I would have to pass. However, I see a vehicle coming down the left lane behind me at 75 mph. There's that point where you think "ok, do I pass this guy, which would make the driver behind me slow down, or do I slow down and let the other guy pass me before passing the guy in front of me?"

I always feel guilty if I choose option A and pass, making the other car slow down. I always try to make myself feel better by saying that the other guy was speeding, so technically he was breaking the law and should be punished in this fashion anyways. However, wouldn't there be justification to do it since I would have to slow down in option B, which would inconvenience ME?" Maybe this is one of those true tests of nature to see how generous a person is, haha. Or, would the blame be passed on the guy in front of me that's going too slow that caused the whole situation? Since if he sped up, it wouldn't inconvenience either me or the driver behind me. I guess this is similar to the German trucker pulling out from behind another truck that itsjustagame commented on. Although over there, there are no speed limits so maybe a little different to my justifications.

[theholycow]

The guy going 65 is not to blame for anything. Maybe the limit is higher than 65 there, but the limit is not the minimum, it's the maximum. I can never blame someone for obeying the legal speed limit even when I think it's too slow...and people wanting to go slower when there are multiple lanes should not be pressured to go faster.

The decision to save your own gas and time or the 75mph guy's gas and time is muddy but unimportant. It's not worth much either way. The guy going 75mph probably isn't as worried about his FE and speeding tickets, but OTOH he has that lane fair and square while you cutting him off is a little rude. IMO if you can do it smoothly then go for the pass and then yield. I usually speed up so I'm not being quite as much of a jerk.

[KU40]

Oh, I guess I forgot to mention that our speed limit is 70. And I wholeheartedly agree that the speed limit is a maximum, not a minimum. I argue that point all the time. I was just carrying the situation further, I'd never personally blame the guy going 65. I'd commend him, if anything.

[GasSavers_RoadWarrior]

I think it could be argued that due to the general principle that "vehicles already on a road have the right of way" then similarly vehicles already in a lane have the right of way. Whether the right of way holds only for legal speeds or not is the matter for conjecture. However be that as it may, the reason for speed limits is partially because 99% of drivers are not equipped with the knowledge and experience to be driving above those speeds. The knowledge and experience required is in part to be able to drive within the limits of the car and the limits of other drivers sharing the road, and being absolutely prepared to do whatever it takes to avoid an accident whenever a slower vehicle pulls out into "your" lane. Ergo it is the responsibility of a driver who wants to drive in excess of the average speed to anticipate the reactions of other drivers such that he is responsible for their and his safety at all times.

Sure we complain about the "idiot" pulling out at 30 who made us waste gas, but if we complain about the idiot pulling out at 30 who made us rearend him, we are merely admitting our failing to anticipate the actions of other drivers, to drive within the capabilities of our vehicle and to effectively and safely manage the space around it.

[Snax]

I always try to anticipate slow downs from slower traffic and take maximum advantage of it with a long glide into a draft. Otherwise I simply speed up to avoid holding up others in the passing lane.

One of the happiest days of my life was when I watched a CHP pull somebody over for obstructing the passing lane!

[KU40]

I tried something new today on my way to work. I normally go the speed limit, 55, on the road I take. But invariably I get followers and sometimes passers. Well today I let somebody pass me that was going about 60-62, and I sped up and followed him the rest of the trip (about 3/4 left) so that I could draft. I'm going to do this for the rest of the tank if I get a chance and see if I get any significant results (with a grain of salt since it is only one tank, and plus I doubt I'll be able to do it every trip). The gas gauge didn't seem to move, so that's promising, especially for the extra speed we were going (relative to how much it would move by myself at that speed over the trip). But it does fluctuate a decent amount going up and down hills, so it's really hard to tell. But I wonder how the guy felt when he passed me so easily then I proceeded to follow him? haha.

[theholycow]

Draft this...

[Mayhim]

In which country would it be easier to get a vehicle operator to pay attention to the task at hand, drive well, and drive safely:

Country 1 - A country of 82m people well known for their attention to detail and proclivity towards regimentation.

Country 2 - A country of 302m people well known for not paying attention, a need to apply makeup and finish dressing on the way to work (for which they are already late), eat on the run, not pay attention to the task at hand, and desire, the NEED, to be the most important person in a 25 yard radius.

The next question would be how likely is it that drivers from country #2 would ever allow themselves to be forced into becoming more like country #1.

Drafting in country #2 might be dangerous since the drivers are so erratic. I would only draft large trucks that can't change direction or speed quickly.