With winter in full swing and icy, snow packed roads upon us, we thought this would be a great time to talk about how to safely drive in these conditions.
First, let’s take a look at the technical side of things. Coefficient of friction – what is it and why do I care? For all the non-engineering folks out there, coefficient of friction is a term (think number) which represents how slippery something is. In our case, we want to know the relationship between the roadway and vehicle tires. During normal conditions, a sunny warm day here in the high desert, one could expect tires to grab the roadway with a coefficient of friction (f) of about .70. When the roadway is wet, that number is reduced to about .55 to .60. When the roadway is icy or snow covered, it is reduced even further to about .45 to .35.
So what exactly do those numbers mean? Essentially, the lower the coefficient of friction, the more distance is needed to stop a vehicle. Without going into the math, let’s take each of these surfaces and look at them individually at a speed of 25mph:
- Normal driving conditions with an f value of .70 – the vehicle would stop in about 32 feet.
- Wet roadway conditions with an f value of .55 – the vehicle would stop in about 41 feet.
- Icy or snow packed conditions with an f value of .40 (median) – the vehicle would stop in about 57 feet.
The difference between dry and icy roads is about 25 feet. Of course these are mathematical minimums; more distance may be needed depending on other factors.
So what can I do to help prevent a crash during poor weather?
Now that we have gone through the boring math part, how is this information put into practical use? The most important things to do in inclement weather conditions are as follows:
- SLOW DOWN!!!!!!!!!!!! Speed is your greatest enemy during bad weather. The posted speed limit is likely not a safe speed to travel during this time.
- Increase following distances. As explained in the examples above, additional distance is needed. Remember, distance is your best friend.
- Allow more time to reach your destination. This allows points one and two to work for you.
- Avoid situations which require hard or emergency braking. If this does happen, DO NOT pump the brakes if your vehicle is equipped with an anti-locking braking system (ABS). The computer in the braking system pumps the vehicle’s brakes for you, and much more efficiently than a human is capable of doing.
- Avoid sudden steering inputs. This will cause the front tires to slide in a straight line rather than the intended direction.
- Avoid hard acceleration. If the drive wheels start spinning, there is no traction. Use traction devices, such as tire chains or cables, if conditions require them.
- Check tire pressure and tread depth. Make sure they are within the manufacturer’s tolerances. Good tires will aid in gaining traction for acceleration and deceleration.
- Depending on where you live, consider purchasing studded snow tires for your vehicle.
- If you do not need to be out in the poor conditions, stay at home.
Some common myths:
- I have four wheel drive, all-wheel drive or front wheel drive; I can drive as fast as I want in any weather conditions.
- FALSE – Four wheel or all-wheel drive will help with traction to get going; it won’t help you when you try to stop.
- Front wheel drive is fantastic in inclement weather, but just like four wheel or all-wheel drive, it is great for gaining traction, but is no better than any other vehicle for stopping.
- I have ABS, I can stop on a dime anytime I want.
- FALSE – The ABS system will still allow wheel lock up (although not for long), causing sliding of the tires. However, it may allow steering input to be more effective.
Winter weather conditions can make driving a little trickier. Allowing yourself extra time to reach your destination and following a few safety tips will help minimize the risk of a traffic crash. Always drive within your abilities and those of your vehicle. Buckle up all occupants and drive safely by following the above recommendations. Finally, always be on alert for those drivers who are not as courteous as you.
Martin Snowbarger has been a law enforcement officer for 18 years. He’s worked for the Farmington Police Department for 15 years and in Raton, NM for three years. Officer Snowbarger has been with FPD’s Traffic Division since 2003 and has been a Certified Child Passenger Safety Technician and Traffic Collision Reconstructionist for 11 years.