Is it safe for a truck driver to speed on the highway?

No, it is not safe, especially in bad weather. If it is snowing, a truck speeding is prone to sliding on the road which can cause an accident.

What causes most problems is when a driver exceeds or impedes other traffic. It's safe when all traffic maintains the speed limit or other speed safe for conditions.

Trucks weigh 40 tons so they should NEVER be traveling as fast as cars and a few years ago the DIDN'T.

But bribes from large trucking companies and unions paid to politicians changed all that a few years ago.

The braking distance is what determines safe speed limits and a car can easily stop in half the distance of a 18 wheeler.

And with todays wet behind the ears millenial truckers, it's a 4 lane slaugher house

No and I will tell you the primary reason tires on any car or truck at a certain point can explode. Because of the centrifugal force of them spinning around and around the rubber literally flies apart.

If this happens you lose control of the vehicle and cause a major accident

Absolutely, the laws of physics state the heavier and faster an object moves the easier it is to stop and change directions. 

<facepalm>

As safe as it is for anyone.  The driver of a big truck generally can see further than others and has way more experience.  The truck itself probably does not maneuver as well, including braking. 

 I would worry about others a lot more. 

yes