Defensive Driving Tip 2:
The speed limit is the speed limit when conditions allow.
If the metal sign by the side of the road says Speed Limit 45 MPH, that means that 45 is the safest maximum speed when the driving conditions are perfect: during daylight hours, when the traffic is light, and when the weather is good.
When conditions aren’t perfect, the posted speed limit is actually too fast to be safe.
And let’s be honest: conditions aren’t perfect most of the time.
slow down below the posted speed limit because visibility is reduced and it’s more difficult to see danger coming. Our eyes are our greatest tool for detecting oncoming danger on the road, and any condition that limits visibility — such as darkness, fog, curves or hills that obscure the road — makes it harder to see oncoming danger.
This increases the chances of crashing into something hard, dangerous, and expensive. By slowing down, you’ll increase your reaction time if faced with an impending crash and you’ll reduce the damage caused by a crash if you do have one.
When traffic is heavy,
slow down below the posted speed limit because the dangers of collision are increased. More cars on the road mean more sources of possible danger. And more drivers that you need to be aware of and watch out for.
When the weather isn’t good,
slow down below the posted speed limit because your car will be harder to control. Wet or icy roads reduce your traction with the road, which means you’ll have less control of your vehicle. Less control while steering, and less control when stopping. What would be a gentle curve on dry pavement can easily become a swerve into the next lane if the roads are slick.
And the amount of time you need to stop on a dry road increases greatly when it’s rainy, and even more for snow or ice.
Whenever you have to drive in bad weather, keep yourself safe by slowing down below the posted limit and increasing your following distance.
Why Speeding is Dangerous
When talking about driving at high speed, the first thing most people think of are speeding tickets. In fact, if you search online for words like “speeding” or “high speed driving,” most of what you’ll get will be advice for beating a speeding ticket or ads for lawyers who specialize in moving violations.
But, to be honest, the risk of getting pulled over and ticketed is relatively minor when compared to the dangers of driving faster than conditions allow. High speeds make it so much easier to be in a crash and seriously increase the amount of damage any crash will do to you, your car, and anyone else who happens to get in the way.
Remember the old slogan for the Thermos bottle? It keeps the hot things hot and the cold things cold. Well, speeding is like that. Higher speeds may make the fun part of driving more fun, but it also makes the dangerous parts of driving more dangerous.
At higher speeds, brakes have to work harder and take more time and distance to stop your car.
A following distance that’s dangerously close at a lower speed is even more dangerous at higher speeds because you’ll cover that distance so much quicker if the car in front of you stops suddenly.
If there’s even a slight problem with the steering or the alignment of the tires that makes your car pull slightly to one side or the other, this pulling is effectively increased at higher speeds. At 20 mph, you may notice your car wanting to drift toward the next lane and can correct it with the steering wheel. At 60 mph, you may notice it just as quickly, but in that same amount of time your car will travel three times as far, putting you in the next lane before you realize it.
One truly serious aspect is the effect high speed driving has on force of impact. This is the formula that describes the amount of damage from a crash, and it’s a scientific way of explaining why a high speed crash does so much more damage than a crash at lower speeds.
The actual formula for force of impact is this:
Force of impact = one half of mass times velocity squared
Physicists may cringe at this description, but this basically means you take one-half the weight of something and multiply it by its speed squared (that is, the speed multiplied by the speed). For a 100-pound passenger in a car going 30 mph, it works out to 45,000 foot-pounds of force.
½ of 100 lbs. x 30 squared
50 x 900
That’s 45 thousand foot-pounds of pressure! That’s how hard our 100-pound passenger will be thrown around if there’s a crash at 30 mph. Or how hard they’ll hit the dash with a safety belt and airbags.
And this is multiplication, remember. Increase either the weight or the speed by even a little, and it effects the total force of impact. Let’s increase the speed by just 5 mph and see what we get.
½ of 100 lbs. x 35 squared
50 x 1225
All of this explains why getting hit by a heavy truck does more damage than getting hit by a runaway shopping cart: more weight means more force which means more damage.
And high speed affects the force the same way. Walking into a parked truck is not nearly as damaging as getting hit by that same truck going 60mph. The weight may be exactly the same, but the increase in speed increases the force of the impact.