Driving a tanker truck is more dangerous than driving a truck carrying non flammable liquids or gases.
If you're driving a tanker truck hauling milk then that is not as dangerous as hauling gasoline, propane etc in a tanker truck.
Still driving a tanker truck can be safe as long as you do your best to avoid a crash.
Drive carefully especially when there is ice, snow etc on the road and watch your speed and avoid crashing into other people.
A lot of tanker trucks cover millions and billions of miles on the roads delivering propane, oil, gasoline etc without any accidents or danger to other people.
So it's pretty safe to drive a tanker truck but at the same time it can be dangerous depending on what you're hauling.