As long as they don't break any rules or crash it's fine. Everyone plays this game in their own way. This game may be intented as a simulation, but it is clear the majority of players don't play as such as almost nobody follows the speed limit. And that's fine, just have fun playing! Personally, I drive 110 as much as possible, but I have to slow down for the corners. This ofcourse depens on the cargo, as some tip easier than others.
I'm not convinced adding more lanes will do anything to reduce the amount on crashes. The best example is around Calais between the city and the first set of traffic lights. The two directions are separated by a guard rail and there's two lanes in each direction, just like a possible new CD-road. Yet, there are always crashes and blockages on that road. People who use that road want the chaos and will continue to create it, no matter what. Fighting it is wasted effort.