An AWD system could break traction at either axle, depending on its design. Locating the engine up in the crumple zone ahead of the passengers can offer some added protection, but savvy engineering and materials science make modern mid- and rear-engine cars just as crashworthy as front-engine ones.
As for enhancing the driver's ability to actively avoid an accident by driving out of a dangerous situation, a neutral weight balance and a low polar moment of inertia are important, so an argument could be made that a mid-engine RWD or AWD vehicle pencils out as "safest. We can recommend wonderful driving cars with each of the above drivetrains, but the engineering and driving-fun decks are stacked against FWD. Blame the "friction circle.
That means that powering out of a turn is far less satisfying in a FWD vehicle. Of course, as total engine power and torque rises to a point that threatens to overwhelm two tires, AWD becomes necessary to safely or more cleanly put power down when exiting turns.
As noted above, only AWD vehicles can take full advantage of every ounce of onboard mass in generating accelerative friction.
But remember that mass, friction, and rotational inertia are all inherent enemies of acceleration, and AWD systems add a lot of each. So just as in the winter traction example above, it's highly likely that—at least for vehicles with less than horsepower, fitting a set of drag slicks or dry traction-optimized summer tires to a RWD vehicle might allow it to easily out-drag a similar AWD vehicle on all-season tires.
Pros: Extremely efficient in terms of cost, mass, space, and fuel consumption with engine located near drive wheels and no excess rotational inertia or friction from driveshafts; locating powertrain weight over the drive wheels is good for traction; safer understeer is more likely in power-on traction-loss scenarios; locating engine mass in front of the passenger compartment might improve crash safety.
Cons: Tires tasked with acceleration have less friction available for turning and can wear out more quickly; heavy front weight bias compromises handling responsiveness.
Pros: Allowing the front tires to specialize in steering while the rear tires do the driving vastly improves both steering feel and ultimate cornering grip; mid- or rear-engine : engine weight over drive wheels plus dynamic rearward weight shift during acceleration optimizes accelerative traction. Cons Front engine : Reduced foul-weather traction compared to FWD and AWD on equal tires and propensity toward oversteer; added mass, cost, friction, rotational inertia of driveshaft, and gearing.
Sure, the robust traction is helpful when you need to get going, but stopping is another story. Four-wheel-drive and all-wheel-drive cars are involved in icier condition-related accidents than their lighter two-wheel-drive counterparts, and their drivers' misconceptions about the limitations of their 4WD and AWD drivetrains certainly plays a part.
Even on dry streets, heavier four-wheel-drive and all-wheel-drive vehicles require more distance to come to a complete halt. When driving through winter weather, you can't go wrong with a set of winter tires. A set of dedicated snow tires should be budgeted into the purchase of any vehicle if you live in an area with wintery weather. Snow tires vastly outperform all-season tires when temperatures dip, and ice or snow covers the road.
Numerous independent studies have shown that good tires play the largest part in determining a vehicle's safety performance when driving through snow and ice.
That is because snow tires are made from a softer kind of rubber than standard tires. Their more pliable texture enables superior traction when the temperature drops. Besides, winter tires feature specialized treads that are designed for carving into the snow and ejecting it out of the way. Snow tires are embossed with a three-peak mountain and snowflake logo, so it's easy to see if the tire you're looking at passes snow performance standards and is rated for winter driving.
If you are mainly looking to drive in the city, a two-wheel-drive car is all you need to zoom around town. Throw a set of winter tires in places with occasional snowfall, and it will perform surprisingly well. This is the cheapest option since all-wheel drive and four-wheel drive vehicles have higher pricing right out of the dealership and are less fuel-efficient, leading to increased expenses down the line.
A front-wheel-drive vehicle is more versatile and less prone to oversteer. If you live in a warm, dry climate and are a performance enthusiast, a rear-wheel-drive car might be right for you. A two-wheel-drive truck may also be the best choice if your primary concern is towing or hauling the maximum amount of weight. Nothing beats the versatility of an all-wheel-drive vehicle when you want a mix of urban driving and rural performance. All-wheel-drive cars are jacks-of-all-trades and can weather harsh winter conditions when equipped with a good set of snow tires.
That is why Subaru enjoys such popularity in the Northern US. The car will slide on the drive axle, in what is known as an understeer or oversteer manoeuvre. When the drive axle loses cornering traction, directional control is also lost. This is not the case for the true AWD vehicle. Because the AWD only transmits half the drive force on each wheel, it has greater grip available for cornering forces on the drive axle.
The AWD can, therefore, withstand much higher cornering forces than the best two-wheel drive car. This is particularly important in slippery conditions, like driving in rain and heavy city traffic, where grip is reduced and cars are driving close to other obstacles.
Any loss of directional stability can easily result in impact with other vehicles or roadside obstacles. A true AWD car, therefore, offer drivers significant safety benefits in the city, because the car provides the driver with a higher level of control, and subsequently a better ability to avoid potential accidents, even at low speeds when the level of traction is poor.
The short answer is that it depends. Drivers can determine the best system based on the primary use of the vehicle daily commuting or weekend adventuring driving style, geographic location and budget. Both AWD and 4WD will provide better traction than two-wheel drive vehicles in most everyday driving scenarios in winter weather. That means buyers that need to tow heavy loads should consider 4WD. Vehicles with AWD have more confidence and better traction in wet, snow or icy road conditions.
By shifting power to the wheels that need it most, AWD systems help vehicles get started on slippery roads and can even help correct wheel slip when the vehicle is underway to help it stay on the road. It can activate much more quickly and accurately than any human driver.
Four-wheel drive shines in deep snow, mud, rough or rocky terrain as well as sharp inclines or declines. Low- and high-range settings allow the driver to dial in the right amount of power and torque delivery to gain the best traction for the situation. Both systems provide better traction to get going and to stay on the road, but neither helps a vehicle stop. A common mistake that drivers make in snowy or slippery situations is believing that their SUV or truck makes them invincible.
Extra traction does not equal extra stopping power. This misconception often can lead to overconfidence. Vehicles equipped with AWD or 4WD generally suffer a fuel economy penalty due to the extra weight and mechanical resistance of the equipment needed to turn all four wheels. In some cases, the reduction in gas mileage is small but can add up over time.
Many vehicles equipped with 4WD are large trucks and SUVs that already suffer from inferior fuel economy due to their sheer weight and size. Complicated drivetrains also can be more expensive.
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