Knowledge

Why do semi-truck drivers leave their trucks running for long periods of time without turning them off?

This is my truck. I basically live in it. Behind the driver’s seat is what appears on the outside to be some sort of fairing. Well, it’s shaped that way, but what it actually is is my bedroom. There’s a twin size bed back there (my head is just above that little hatch on the left side when I’m sleeping) as well as some cabinets and general storage space.

I have to sleep in there. Sometimes the temperatures are moderate enough to not require heat or air conditioning. Sometimes. Usually it’s either way too hot or way too cold to sleep without some kind of climate control.

Some trucks have auxiliary power units. They’re a little diesel engine running an AC compressor and a 12V alternator, and usually they’ll also have an inverter to provide 120v power for appliances and stuff as well as a fuel-fired heater to keep me warm in the winter. In fact, all but three of National’s trucks have them. Mine is one of those other three.

So when it’s too hot or too cold to sleep comfortably, guess what I have to do…yup, keep that big frickin engine idling all damn night. Trust me, I hate it too. It burns about half a gallon of fuel per hour. At least with the exhaust after treatment systems in use since 2010, the exhaust coming out the back of my truck is cleaner than the air going in the front.

We call this idling.

Trucking companies, the general public, and environmentalists all hate it. But those truck drivers will practically roll up those sleeves and be ready to fight you for it. But why?

There’s a few reasons actually. The primary reason is AIR FLOW. Trucks have very little air flow in them, most especially in the bunk. Air gets very stale, cold, or hot inside these trucks very, very quickly even with the windows and vents open. We like to breathe.

Power. For the most part, trucks are a drivers home for weeks on end. This isn’t the 1400s, people like electricity. When the truck isn’t running, it’s drawing power from the batteries to keep things like our refrigerators, etc running. Weak or dead batteries are a nightmare. Trucks with opti idle will start automatically to recharge batteries but it’s awful for climate control. You’ll be sweating long before that trucks starts itself to cool you off, or warm you up (whichever the case may be). Trucks with APU’’s do a better job at this, but not all trucks have them.

Diesel engines are different from gas engines. Diesel engines are happiest when left running. It takes longer for diesel engines to reach running temperatures than it does for gas. Some trucks just don’t like to be shut down.

And the final reason….time. It takes longer to start our trucks than your car. Your car doesn’t require a safety sweep before starting. Our trucks won’t start without one. And people by nature of life in 2025 are impatient.

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