The continue to run so that the driver can enjoy things like air conditioning, radio, etc. Many of the larger trucks with sleeper cabs have refridgerators, TVs, Computers in them.

nfntjy is correct on some of these. The other reason 18 wheelers are left running is that a large truck uses air for the braking system, (even while parked). The air tank and system can take a long time to be brought up to pressure, during which time they have no brakes. They are kept running to keep the air compressor running and the brake system at full capacity. Edit: I LOVE getting rated down on answers that are over 6 months old. I don't really care if you agree or not. At least be adult enough to back up your piece of shit rating with a reason.

Some of the reason depending on where you are but in winter months, it keeps the fuel warm <return fuel> so it does not gel up, miles from home.

With about 20 years of truck driving behind me, 10 of which were around Europe where I am originally from, I feel at ease to point you in the right direction to this conistant idling problem. The main reason truck engines are left running is simply for the use of heat, air conditioning or power for many appliances now available while on the move. I have, unfortunately witnessed many a truck idling for no apparent reason when the weather is great for sleeping. In the winter I took extra blankets and parked opposite to most trucks at truck stops around the country and simply cut off my engine for the night. Parking this way I did not have to listen to other peoples engines and air blow off valves all night long. If your battery is in good shape and it is not ridiculously cold then there are not too many reasons to leave it running all night. I have parked in the snow before and lept perfectly warm enough through many a cold night. There are after market devices like night heaters that run off diesel fuel and are very quiet. In very cold weather there is a chance that brakes will freeze on the trailer if left on for the night without the engine running. Simply leaving an engine running will supply air circulation round the system and the constant vibration of the engine can also be a help to freezing brake problems. There are many more arguments for and against this subject but I hope this helps.

the reson i allways got from my father when we traveled the country hulling god knows what was because shutting them down every time we got out or pulled off for the night puts alot of extra whear and tear on the engine and other systems

1) heat/ac , 2)fuel return keep diesel warm, 3) in winter takes a while to warm the engine up to running conditions when you wake up, and most important if the damn thing does not want to star again for some reason it is very annoying to wake up to a not starting truck.

Well...during the winter it helps keep the fuel from freezing and also provides the driver with heat inside so he/she can sleep comfortably. During the summer the air conditioning will obviously work for the same reason (and big trucks can become stiffling hot). Among other things there are mobile computers needed for dispatch being run and if the truck's turned off so are the computers, phones, etc. But the biggest reason is for break down. A diesel can be terrible to try and restart if it shuts down and it's just far easier to let the truck constantly run. I personally shut mine off...leaving it run is horribly costly on fuel and maintenance and hard on the environment, but there are times when leaving it run is simply unavoidable. hope that helps you some! Take care

Wear and tear on the engine. Diesels have incredible internal pressures. An engine starting up has no oil pressure. Consequentialy most of the wear on the internal parts happens at startup.

diesel engines are also designed to burn 1 gallon of fuel per hour at idle

I am a long-haul driver - 51 years! In winter months I have a 12 volt bunk-warmer, plug it in an hour before I shut down and turn up the heat as I do my end-of-day log book. Then I shut down the engine and crawl into my -40 sleeping bag with a good comforter over top and I'm good for the night. Can't sleep with my engine idling. I run Montana and Wyoming so I know cold. I keep good batteries in my rig and it always starts first time I touch the key. Idling is for idiots who drive Co. rigs, don't pay for the fuel and don't care about the environment. I also park my unit as far from reefer rigs as possible. Ted

they keep the motor running to keep heat, or cool the inside, for thier comfort, and to keep the fridge., and tv. going.

Some states have already banned this. more will follow. More truckstops have hookups now and the new trucks 2008 is coming out with a new A/C system that cools for hours after the engine is cut off. Changes are been made.

even though fuel is expensive...engines and equipment in diesel big trucks are EXTREMELY expensive. a truck can cost $100,000 or more these days. these engines work better when kept running. some of the biggest damages to engines and components is at start up. would you rather spend an extra thousand dollars a year idling or $20 thousand in repairs... that will be passed on to the consumer:???

Basically the drivers that idle all the time are not paying for the fuel and just don't care. The companies are cleaning up on their labor and the drivers know it. There is no incentive to save fuel when it costs them nothing.

The Fridge has to be running to keep the beer cold :-))

no mainly its because they have refers aka freezers on the trailors and they have to keep the truck running to keep the freezers cold or else the produces thaws THTAS WHY the fridge that holds the beer runs of the trucks battery its no biggy but the refer is to big to run off the battery

It depends on the driver. There are many reasons to keep it running. you'll never get a correct answer to the question. Getting truck drivers to agree on one thing is impossible, it's been plaguing the trucking industry from day one and it's not going to change. Good question and keep asking trucking questions your sure to get many hits on it.

sometimes, consider this, take a metal box the size of a truck and try to sleep in it on a 90 degree F day!! ac, enough said. some truckers now have aux engines to run heater and ac

To run the ac or the heat :)

Simond gave a good answer. Now, with 20 years behind me as well, II can tell you that my current truck has an APU on it. It is about the size of a lawn mower engine, and gives me heat, AC, and actual electrical outlets in my truck. The truck idles at about 1.8 gallons per hour, where the APU uses about 3/10 of a gallon per hour. Obviously, the APU is much more economical. Diesel engine are constructed differently than cars, and in the older models, starting and shutting them off all the time was hard on the engine. When I started driving, you NEVER shut the truck off if you were going to be stopped for less than 30 minutes.

Because they literally live inside those trucks and they need to keep the AC/heat going when they're sleeping, resting and even running the electronics and other equipment/appliances they have in there

It is partly as 'rinky dinky' said to keep the a/c or heater running. But as an ex-trucker, I have found many many times that the trucks are running mostly to keep the battery charged so the world can see ALL their wonderful clearance lights. The next reason is force of habit (and they don't buy the fuel!). I recall waiting overnight in Calexico, CA to clear our load from Mexico. It was very hot, so we took a room at the Super 8, which had good truck parking. There was another trucker checking in at the same time as us. He asked if he could leave his truck out front instead of the truck parking lot, and received approval to do so. We went out to eat and when we returned to the hotel, there was his EMPTY truck sitting in the lot just a chugging away.

The trucks are left running, not because they are hard to start, but to keep the driver comfortable. The truck needs to run in order to operate the heating/air conditioning, TV, refrigerator, etc. Some trucks can bypass this these days by installing generators on their rigs. Some companies are even offering this option on their company trucks now. Mostly due in part to the rising cost of fuel. Drivers do not run their trucks to annoy the general public, they run them to stay comfortable, just as you would in your own house.

As one chap has stated there are SOME good reasons for leaving the engine running. But a driver should be aware of where & when they will be on route. Thermo clothing, cab heaters, £ antifreeze for the `air system` are available. Manufacturers can insulate the cab very cheaply. But as has been said- if your battery is poor,or indeed charging system, then you may have to keep the motor running, also on a diesel there is a `spill back` fuel return, this `warmed fuel` will stop `waxing up ` of the fuel line. This uses fuel of course, but repairs often come down to whether the truck is `owner-driver` or a company vehicle.Truck do opperate in very cold clime, like Alaska & Siberia, I`ve heard of tires failing due to their losing their `elesticity`! I will add that the lot of truckers in all countries is not allways good, they serve the ecconomic drive of the nation, we pay them scant regard!

All diesels are that way, even mine. It takes 1.2 gallons to crank the engine. It comes down to the simple difference between a gas engine and a diesel. Gas engines have constant A/F Ratios and vary the throttle valve (a butterfly valve in the intake) to adjust throttle. A diesel lacks this, and really, it doesn't matter how much air flows in. You adjust throttle by changing your A/F ratio. This is also why a diesel (like my C/K 2500 9k GVWR) will run awful milage when you get heavy on the throttle (and you see some black smoke - partially burned fuel) and gets much better when cruising/idling (25mpg highway, 9 city for my truck w/o a trailer, 22 highway and 3 city without). Compare that with any gas engine. Also, yes, starting an engine is when you get the most wear on an engine - you're turning the crank and moving the pistons without an oil pump! That's why, when we do verification testing, we will start a car every 5 seconds for the length of the test (start, idle for 2 seconds, shut down, start). Plus, it allows us to test in a couple weeks rather than 20+ years!

for comfort options like heat and air no they are relatively easy to start just like turning a key but it is nice to keep from freezing to death in north dakota in the middle of january

most drivers leave there engine running to keep there airconditioning going to keep the cab cool or in the winter to keep the cab warm in perrticular when there trying to sleep they are rerquired to take a 10 hgour break after so many hours of driving , a little hard to sleep when the cab is to cold or worse to hot. j.r. horton

In hot wheather say around 90 to 100 the inside of the truck can be 35 to 50 degrees hotter.

the wear and tear and some dont have the generators on them so they leave it running to stay warm or cool

Mostly to run heat or ac for comfort. If the driver does not own the truck he may not care about the idle time or fuel costs.