Without a doubt slowing down is the cheapest safety you can buy when pulling a trailer. All you have to do is reduce speed to be safer... and it is free! It can even "pay you back" with better gas milage and less wear on your rig and yourself.

Everyone knows this, right? Yes they know but I am not sure everyone really understands it. Have you ever known a trailer "guru" who has added every safety feature imaginable to his rig only to cruise down the highway at 70-80 mph presumably because their "stuff" makes them "safer"? Do they understand the explosives they are carrying on board at that speed? ... the explosiveness of kinetic energy?

The best way I know of to equate the potential explosion of speed in collision is to look at the TV news and see what happens to vehicles caught too close to a bomb explosion. It can pancake a car or truck just like running into a concrete wall. Energy is energy wether it is a chemical explosive or it is in kinetic form. When you drive at any speed you are guiding a bomb.

So what is kinetic energy? Kinetic energy is the mass¹ (weight) of an object combined with its speed. A hammer sitting on your work bench has some energy² that has been absorbed by gravity which we loosely call "weight". The same hammer when picked up and used to drive a nail has weight plus the velocity (speed) applied as you swing it down. It has much more energy this way than when at rest. This weight + velocity is called "kinetic energy". You can quantify the kinetic energy of a moving body (E) by applying the equation below where m = mass (loosely called weight) and v = velocity (loosely called speed).

As an example let's assign a weight of 5000 lbs to your tow vehicle and 3000 lbs to your trailer (8000 lbs total). Now assume a 10 mph towing speed. How much kinetic energy is rolling along there under your seat? Answer: 26,753 ft-lbs³ . 26,753 ft-lbs sounds like a lot and should you run into a wall with this "small" amount of energy your 8,000 lb rig will probably absorb it ok... albeit with an expensive repair bill. However should you elect instead to quickly stop your rig with the brakes you can probbly do it far short of the wall thus saving you from the body shop entirely.

Now let's quadruple your speed to 40 mph and run the numbers again. This time we come up with 428,044 ft-lbs. Wow! now that's a lot. In fact it looks like too much! Reasonable people would assume that the kinetic energy at 40 mph should be four times more than at 10 mph. That would be only 107,012 ft-lbs, not 428,044 ft-lbs So what happened? Is this an error? This is not an error... it is right on. The squaring⁴ of the velocity (speed) dictates a non linear increase in kinetic energy for your rig. Check the graph of speed vs kinetic energy below.

For practical towing purposes we should maybe look at the graph above and think about the difference in kinetic energy driving at 60 mph vs 70 mph. The E at 60 mph is 963,000 ft-lbs and the E at only 10 mph more is 1,311,000 ft-lbs. In other words, increasing your speed only 16% (60 to 70) increases the kinetic energy 36%.. more than double the increase in speed!

Maybe the animation below will make it more clear. Watch the speed and energy balls on the graph.

It is obvious that no amount of safety equipment or driving skill changes the amount of kinetic energy stored in your rig as you drive. Adding better tires, new shocks, an anti sway bar, or better brakes does not remove any kinetic energy... it does not defuse the bomb! It is still there ready to explode should you hit another vehicle or a bridge abutment (at 70 mph our rig has 1,120,000 ft lbs of energy... more than a stick of dynamite). Kinetic energy is there all coiled up like spring ready to toss you over and over and over again should you roll the rig. It is also there to make it harder to bleed off speed when you need to brake. It NEVER goes away unless you slow down!

Why drive like an explosive just because you can?

Conversion factors
1 pound = 0.45359237 kilogram
1 mph = 0.44704 meters per second
1 foot pounds of force = 1.35581795 joules

¹sticky subject converting/describing newtons/mass/pounds but in this case it is ok as pounds for now.
²read potential energy
³although similar to torque, ft-lbs it is used here to convert the physics measure of the Joule to the English measure.... think of it as straight-line torque
⁴multiplying a number by itself