by Lori Straus

While you’re researching your next car purchase, whether new or used, you’ll often come across these three acronyms: 2WD, 4WD, AWD. You’ll likely understand right away that 2WD refers to 2-wheel drive vehicles, where all power is transferred to either the front (FWD) or rear (RWD) wheels. But what’s the difference between 4-wheel drive (4WD) and all-wheel drive (AWD) vehicles? And how does any of this affect the safety of the vehicle you’re considering?

2-Wheel Drive in More Detail

We’ll begin here. This style of drivetrain is the most energy-efficient out of all three styles, because the vehicle only powers two wheels: front or rear, though in most cars today, the front. In addition, 4WD and AWD drivetrains are much heavier and also take up a little space in the vehicle interior—that’s what the hump in the middle of the back-seat floor is.

How 4-Wheel Drive Works

4WD drivetrains mean what they say: all four wheels are driving at the same time. However, this style of drivetrain is typically reserved for trucks, because it’s needed for off-road terrains. A 4WD drivetrain transfers power to both axles equally and ensures that all wheels rotate at the same speed. This becomes an issue for city driving.

For example, when you turn a corner, the wheels on the inside of your turn need to rotate more slowly than those on the outside. But with 4WD, all wheels turn at the same speed. Using 4WD in the city can eventually damage your drivetrain, which will end in expensive repairs.

Lastly, most 4WD trucks built today allow the driver to switch between 4WD and 2WD. This lets these trucks be driven in the city, but unless the snow is excessively deep or there is deep water from recent flooding, 4WD won’t help in city driving.

All-Wheel Drive for Everyday Driving

Most cars with all-wheel drive will usually transfer most of the power to two wheels until the car senses that those two wheels are losing traction. Then the all-wheel drive system will transfer some power to the other two wheels to try and improve traction. Unlike 4WD systems, though, AWD is fully automated: the driver doesn’t intervene.

Does AWD Make Winter Driving Safer?

This is the ultimate question. Because AWD can give you the impression that you have better traction, you might think that an AWD drivetrain is safer. But in fact, it’s winter tires that improve your traction in the winter. AWD systems help keep you from getting stuck and can help you accelerate quickly if you need to, but drive according to the conditions, not whether you have an AWD vehicle.

Know Your Needs

One point to remember: some car manufacturers use 4WD and AWD interchangeably. If you’re considering a vehicle with either capability, ask your sales rep to explain exactly how the vehicle works and how it will work with your driving needs. Make sure to choose a vehicle that best suits your lifestyle and budget, lets you afford winter tires, and helps you drive safely. Those factors, in the end, are the most important.