That makes sense. AWD handling is so much better in winter conditions that I feel it has to make it less likely to crash.
The big advantage is when accelerating. It's a nice quality of life feature. I typically switch to AWD when I move to winter climates. It's not as safe though, _especially_ if you have little enough training that you're relying on intuition to make that conclusion that AWD must be safer.
Now if you happen to be really good at driving, it's even safer because you can recover from a slide faster, again because of the increased traction during acceleration. Once your tires have traction again the additional traction moves you out of the slide faster.
The only problem here is people going too fast which can happen with any car.
In Michigan, like clockwork the AWD SUV’s would go flying off the elevated freeways into the deep snow at 50mph in every storm.
Personally, I'm comfortable driving anything but a RWD pick-up truck with no payload in snow and ice, try to drive at an appropriate speed for weather conditions, and rarely have trouble.
I love driving up to Tahoe in a blizzard. I'll happily be doing 25 mph going uphill as it's roughly the safe speed for the conditions. I'll constantly be passed by AWD SUVs going 40-50, while going uphill.
Then we summit Donnor Pass. I'm still cruising along at 20-25. You can see the fear in these SUV drivers' eyes as they start sliding down with their "all season" tires. Invariably, they'll then slow to 5mph with their flashers on in the right lane and I can cruise down t 25mph and pass all the cars that flashed at me or gave me a look going up.
It is baffling to me that CA loves to enforce chain control but exempts AWD without actual winter tires from it. It's almost never the 2wd drive cars with chains that pile up, it's always the AWD SUVs. If you're going to enfore chains, at least do it usefully and only exempt actual winter tires. Then it would be useful, not just a massive slow down.
In a very long winded way, couldn't agree with you more!
I'm struggling to come up with a reason why the faster acceleration itself would be a safety issue (maybe trying to get out of the way of a truck that can't stop or something? it seems niche), so let's instead look at the increased control during acceleration (from less force on the steering tires).
When does that matter from a safety perspective?
In a straight line, it doesn't. Let off the gas and try again. No matter what you do, you're going to go in your intended direction of travel or stay put.
So that brings us to accelerating around a curve. Don't do that on public roads in normal cars in winter conditions. The risk profile is terrible. If you misjudge it just once you're in a ditch.
Even your slide example seems strange. Could you describe the conditions of a slide where applying power helps you gain traction faster than not applying power? The only thing immediately coming to mind is reducing the yaw force in certain oversteer scenarios with a counter-steer and a bit of power, but in that case whether AWD helps or not is extremely situational and depends on the exact build of the car.
But aside from all that, I think there is a scenario where applying power can help gain traction faster. In a FWD, if someone has gone into a corner too fast, or encounters a more slippery surface than expected, and the vehicle starts to understeer straight-ahead, I have heard of the idea of accelerating to get the vehicle to continue around the corner. The turned front wheels, while still not gripping properly, spin and pull the front in the direction of the corner more than would happen from just braking or maintaining speed. I'm probably not explaining that well, and it doesn't sound safer than just braking! I am fairly certain I remember seeing something which I think is related, in the Owner's Manual for some old front-wheel drive Japanese sports car. Something like an old Honda Prelude or a Toyota Celica. They played up the safety of FWD "pulling you through" the corner. None of this makes the case for AWD though. I can only see the advantage I wrote above about accelerating earlier/harder, and I think you already addressed that.
Is this dumb in winter, or dumb generally? I was taught to do this.
- Smaller turning circle because the front wheels can turn further without complicated engineering.
- More traction when accelerating on a wet surface, due to weight transfer backwards. (1)
- Usually better weight distribution due to engine layout.
There are other downsides in addition to what you mentioned:
- Any scenario where you will definitely lose traction, then rear-wheel drive becomes harder to control. There was an old Top Gear episode with a steep grassy hill, and drivers of the RWD cars could not get up it. (2)
- The transmission tunnel required for RWD
- Reduced fuel economy due to having to turn the power 90 degrees (assuming the engine is mounted in the front). (3)
1) This one may sound like unnecessary acceleration, and it probably often is, but there are situations where it can arise, especially if you prefer older cars. There is one particular hill I used to encounter frequently, where you are trying to turn onto a main road, so you want to accelerate fairly briskly to avoid waiting for a huge gap in traffic. On economy tires, in the wet, you can easily reach the limits of FWD. I would see many cars time a gap, and then have to rapidly decide to give up on it when their acceleration was much slower than they expected due to wheel spin. I think there may have been bus lane paint on the road too, but I'm not certain. Obviously AWD is even better than RWD for traction, but at that point, that is usually only when requiring rapid acceleration.
2) I suppose with perfect/computer assisted driving, RWD would out-perform FWD.
3) I once searched, and had a very hard time quantifying this, but it is almost certainly a few percent, and perhaps more. There are also weight differences involved because of the long drive-shaft, but I think the effect is larger than that. It is very hard to find an apples-to-apples comparison.
If you want to maximize speed through a curve plus straightaway, you should pick a path through that curve minimizing curvature at the end so that you are able to accelerate out the end of the curve. As a reasonably good approximation for normal driving, your tires have the same traction regardless of the direction of the load being placed on them. That gives you a budget of net force you're able to apply. If you're near the sideways force limit going around a curve and add acceleration (or braking -- always do your braking before you enter the turn, or gradually reduce it as the curvature increases), the wheels with those extra forces will break traction. The solution is to apply that acceleration at a point of milder curvature.
Taking that idea back down to safe driving speeds, the same idea exists when considering crossing a margin of error rather than the ultimate slip threshold. All else equal, accelerating as you come out of a curve, if you've chosen your path through the curve correctly (really important to get that right; there's a curve back near my hometown which has taken out half a dozen people over the years because its curvature increases at the end and they haven't planned for it), will minimize your time through the curve and the following straightaway at your chosen safety threshold.
However, all of that is predicated on minimizing time assuming perfect knowledge and perfect driving. The acceleration itself is actively harmful from a safety perspective. In FWD, the wheels losing traction are the ones connected to your steering wheel. That's not ideal. In RWD you're prone to oversteer and spinning out of control. In AWD you can get either or both of those failure modes. Moreover, navigating typical curves, you're so far from slippage that the technique of accelerating at the end just means you'll go from the speed limit to something greater. For winter curves, the margin of traction uncertainty is so great that you can't gain much from accelerating out the end anyway (and have a pretty bad risk profile -- accelerate on a straightaway and slip a bit and with a bit of training you're basically fine, slip off a curve and you have a really bad rest of your short life potentially).
Safely accelerating in a curve is a learned skill though, and most people don't care that much about driving. Unless it looks like they're interested in more depth, my advice is always to brake before the curve and accelerate afterward. It's safe, fast enough, and easy to remember.
Misconceptions like this are why people are lulled into a false sense of security.
Do you own an AWD vehicle? They outperform 4x4s on everything except rock.
Absolutely not. My 2015 Subaru will selectively apply braking to individual wheels for traction control. That is an advertised feature, even.
AWD can shift power back and forth between the wheels. Its wheels do not have locking diffs and can turn at different rates all the time. This means you can selectively apply brakes to only tires which have traction to stop, or brake the tires without traction and let the gripping tires do the work to get you moving in trash road conditions.
And that's before you even get into tire consideration.
The "weakest links in the chain" when it comes to snow driving are largely centered around putting motive power to the ground without breaking traction. Think like steep hills, crossing the piled up slush between lanes, getting moving from a stop, etc. Except inn rare circumstances, your "this feels decent speed" is attainable regardless of AWD so it's not like you go any faster.
I can see AWD allowing better engine-braking than FWD in some low-traction situations, but I don't think it would make much difference if trying to stop quickly. I think for modern cars, using engine braking would almost never provide quicker stopping, or more controlled stopping than brakes alone.
Regarding three pedals, you could downshift in an two-pedal automatic too couldn't you?
Are you saying that when when cornering at a constant speed, if a slide starts, the vehicle will rotate differently to a front-wheel-drive or rear-wheel-drive vehicle?
Or that when cornering, if you accelerate enough to spin the wheels, then an AWD vehicle will rotate around the middle?
For the 1st case, when you slide because there is not enough traction available for that speed, on that surface (e.g. driving too fast, or encountering ice), I wouldn't have thought the axles that power is delivered will make a large difference to how the vehicle rotates. Either the front loses traction, or the rear, or both. Wouldn't the weight distribution be more relevant than the driven axles?
For the acceleration example, again I think of either the front losing traction, the rear, or both. Front-wheel-drive would lead to the front losing traction, RWD the rear losing traction, and AWD ... I'm not sure. With some systems, it's plausible that neither the front or rear would spin until both lost traction simultaneously. I tend to think a 4 wheel slide would be similar to understeer in a front-wheel drive car, but perhaps a little more like sliding sideways out of the lane, rather than plowing straight ahead. This doesn't seem to me like rotating around the middle, so I feel like I'm missing something.
To be honest, the idea of AWD making the vehicle rotate around the middle (and rear-wheel-drive making the vehicle rotate around the...front?) seems like the persistent and widespread idea of AWD allowing a vehicle to corner faster at a constant speed. My thought is that it's a misconception, but I'm happy to be wrong!