Are four wheel drive vehicles better because they're safer?

[diesel_john]

How do you feel about the safety merits of four wheel drive?
I think four wheel drive should be safer than 2, but human natural being what it is, it seems like the more traction(friction) people have the more unsafe situations, they can get into.
I mean, put 4WD in an Audi and some ass tries to drive it up a ski ramp in the Alps. FourWD vehicles have to use 4WD to handle as well as frontWD. The vehicles are made incorrectly. When in 2 wheel drive the heavy end should be doing the driving. How difficult is that?

[larrydag]

I think 4WD depends on the terrain scenario.

If it is rocky, dirt road, snowy, or loose gravel I believe 4WD can have its merits.

If you are on ice forget about it. There isn't a *WD that can handle ice. You need traction first.

If you are doing highway and city driving I think 4WD doesn't buy you anything. In fact it just causes more wear and tear on the car/truck and that on its own could be a safety risk.

[Who]

A true four wheel drive system can be quite dangerous. By true, I mean a vehicle with a transfer case that turns th front and rear axles at the same speed. The front wheels travel farther than the rear wheels unless you only drive perfectly straight and this causes axle wind up. In deep snow and mud this isn't a factor but on wet or icy roads it is, and on dry roads it can damage the drivetrain.

Now a good all wheel drive on the other hand is safer than anything.

[trebuchet03]

Originally Posted by diesel_john

How do you feel about the safety merits of four wheel drive?
I think four wheel drive should be safer than 2, but human natural being what it is, it seems like the more traction people have the more unsafe situations, they can get into.
I mean, put 4WD in an Audi and some ass tries to drive it up a ski ramp in the Alps. FourWD vehicles have to use 4WD to handle as well as frontWD. The vehicles are made incorrectly. When in 2 wheel drive the heavy end should be doing the driving. How difficult is that?

I'm going to be a stickler for words, for a moment....

Saying "better traction" is a misnomer. Traction is the friction between the tire and road which is a function of the coefficient of friction and the weight normal (pointing straight out) to the ground (which may be inclined). Assuming the same weight for a 2wd and 4wd (I know, 4wd is a little heavier, just bear with me). Both vehicles have the same amount of traction...

Now, the more drive wheels you have, the better ability a vehicle has to track. Tracking is the ability for a vehicle to maintain a straight line while accelerating. I think that's where confusion comes in, as the words are very similar....

Now, that aside.... are we just talking about 4wd - or is awd (driving 4 wheels when slip is encountered) on the table too?

4wd is, hands down, better at climbing an incline. You've split the torque between wheels, so it takes more power to overcome the available traction and start spinning your wheels.... That said, the bulk of the population doesn't live in conditions that requires this....

Story time...
My da has a Honda Element - he bought it as a wreck and rebuilt it.... It happens to be awd.... I've only seen it engage once, because his foot slipped off the clutch while launching..... Even in the torrential rain South Florida gets (and the way he drives), the thing doesn't come on.... He does drive on construction like type of sites (lots of loose gravel/rocks, sand etc.) - and it still never comes on....



Now... research time.... The first thing I found was from Australia....

Less accidents - but more fatalities


More roll overs


People injured where 4wd was involved


With respect to keeping up with the neighbors for your suburban monster.....

Even though 4WDs are becoming more popular on urban roads, the majority of 4WD crashes occur on rural roads and this number has been increasing. In 1990, 57 per cent of 4WD crashes occurred on rural roads and by 1998 this had increased to 68 per cent. An almost even proportion of passenger car crashes occurred on rural and urban roads (51 per cent and 49 per cent respectively), and this ratio has remained fairly stable between 1990 and 1998.

On rollovers

Table 2 also shows that the proportion of 4WDs that rolled over without a previous collision was over three times the proportion for passenger cars (21 per cent and six per cent respectively). These crashes mostly involved single vehicles that had driven off a straight or curved road and rolled over. It is unlikely that the increased incidence of roll-overs can be fully explained by different terrain and roads used by 4WDs compared with other vehicles.

So saying "safer" is a catch 22.... The stats say you're less likely to get into an accident... But, when you do, you're significantly more likely to die. And that said - looking only at passenger cars, the odds of getting into an accident in a rural OR urban setting are even. Looking only at 4wd - you're more likely to get into an accident in a rural setting. AND, if you get into an accident with someone else - you're more likely to kill them... statistically

I'd also like to point out cyclists -- 4%

And interestingly - something that has no bearing on the mechanics, the the type of driver....

The proportion of alcohol intoxication amongst 4WD drivers involved in fatal crashes (29 per cent) was higher than for all other types of vehicle operators (for example, 21 per cent of passenger car drivers involved in fatal crashes had a blood alcohol concentration of over 0.05g/100ml);

I'm not calling anyone here a boozer... but wtf? No disrespect to anyone from Australia either

----
What tre thinks...
It's a feeling. Airbags, crumple zones, 4wd, ABS, traction control, big heavy vehicles etc. etc. makes us feel safe. The safer you feel, the more detached you are from risk (but that risk is still there). If we were to pack nails into our airbags such that the cost of getting into an accident was so severe (painful death) - we'd be taking a lot less risks. I'm not saying we should do that - that's a pretty low outlook for human life - it's just an example. I'm also not saying we should take these safety features away either - ABS has saved my but once already I'm offering the irrational rationale as to why we've reached the point where certain words = safe despite the number of people that die. I mean, it's right there - more people die in motorcycles, heavy trucks and 4wd's even though 4wd vehicles have less accidents.

It's not just the physics here - it's the psychology of the word.

I call it less safe by relative comparison to passenger vehicles.

and that's what tre thinks


as always
citation: http://www.tenders.tas.gov.au/domino...c?OpenDocument

[trebuchet03]

Originally Posted by trebuchet03

I'm going to be a stickler for words, for a moment....

Saying "better traction" is a misnomer. Traction is the friction between the tire and road which is a function of the coefficient of friction and the weight normal (pointing straight out) to the ground (which may be inclined). Assuming the same weight for a 2wd and 4wd (I know, 4wd is a little heavier, just bear with me). Both vehicles have the same amount of traction...

Following up on my own comment

For that reason - tire selection is paramount. I'm not going to drive a snow tire in summer and I'm betting no one here drives summer tires in the snow. Similarly, I don't drive summer tires because of the volume of rain (and how quickly it falls) in my region.

Tires are key - plus, we have excellent roads just about everywhere.

[DifferentPointofView]

I kinda just skipped through it, but. 4wd is for the back country, not the city. by the time you have to get anywhere in the city, the roads have been scraped clean already. on dirt, gravel or my village, they don't have snow plows, so however much snow is in your yard or ice is frozen on your car is how much is on the road till the stuff in the yard melts. then you might need 4wd. if you have to go through fields to get home, get 4wd. And no, speed bumps aren't a reason to get 4wd.

[cbergeron]

"Better" is a relative term.

For purposes of getting high mileage, no, they aren't better.

Having 4 wheels in direct contact with the drivetrain means that you have 4 wheels that are limiting your coasting ability (not just 2).

[DifferentPointofView]

that's why they made a thing called selectable 4wd. you can have 2wd when you want to, 4wd when needed, and AWD when you want as well.

[cbergeron]

that's why they made a thing called selectable 4wd. you can have 2wd when you want to, 4wd when needed, and AWD when you want as well.

My post stands.

All 4 wheels remain in contact with the drivetrain, whether they are engaged or not. There is a gearing mechanism / differential that never lets the wheels roll as freely as they do in a purely 2WD vehicle.

For mileage purposes, you'll rarely (if ever) see an AWD car get higher MPGs than a 2WD car.

[DifferentPointofView]

is this the same as when you put the transfer case in neutral?

I agree though, you will never see a 4wd vehicle that gets better mpg's than a 2wd one. But if you need the 4wd, it's better than full time 4wd.