Truck drivers leave their trucks idling all night long to keep the air conditioner going in the summertime or to keep the heat going in the wintertime as well.
The truck driver is sleeping in the cab of the truck in a sleeping area and in the summertime the inside of the semi truck can get so hot that it could kill the semi driver so they need the air conditioning running to stay cool.
So they idle the engine at night to keep the cab cool while they sleep.
Also in the winter the semi driver uses the engine heat to stay warm.
And in extreme cold some companies mandate that the semi idle at night to keep the batteries charged and keep the diesel fuel from gelling up.
In extreme cold the diesel fuel can gel up and then they cannot start the engine or it can make it hard to start.
So they idle the engine all night long.
In some places they do not allow idling but some do it anyway.
Yes all semi trucks have speed governors on them that are set through the computer.
The speed governors or speed limiters prevent the semi truck from going above a set speed for safety.
Most semi trucks have a speed governor that is set to either 65 MPH or 67 MPH depending on the company that owns the trucks.
The speed governor is also used to save fuel because speeding is not only dangerous but also can increase the fuel consumption.
A semi truck driver that works for a company gets paid by the mile so they have to drive a certain amount of miles in a day so they can make the money.
However the semi truck driver is also limited to the amount of hours the semi driver can stay on the road and they have a mandatory break.
A semi truck driver is limited to 11 hours of driving on the road and then they have to take a 14 hour break before they can get back on the road again.