Why do some trucks have exhaust on top?

The reason is primarily for maneuverability challenges in very old towns with tight roads. Keeping the exhaust underneath keeps the vehicle length shorter and therefore able to make tighter turns. Heavy trucks in North American as general rule have a hood over the engine with the cab behind it.

Why do trucks have exhaust on their side?

Exhausts on trucks point out the side because they can’t point straight out the back (or you risk damaging the exhaust on your departure angle) and it’s illegal for them to exit under the vehicle anywhere (due to concerns of carbon dioxide buildup in the cabin).

Why do semi trucks have exhaust stacks?

What is the difference between American and European semi-trucks?

The main difference you see between American and European semi-trucks is the overall design of the tractor unit. In Europe we usually see cab-over trucks. This means that the cabin is situated above the engine.

Why don’t trucks use cabs in Europe?

In Europe trucks have to deal with narrow streets, winding country roads and cramped parking spaces. Lack of space limitations allowed Australia to use conventional cab trucks too. That is also why Australian highways feature well-known road trains – extremely long distances and straight roads allow semi-trucks to pull up to four trailers.

What does a cab truck look like without the engine?

Without the engine under the cabin, getting in and out of the truck is actually easier, because the cabin is a little lower. This is what conventional cab trucks look like – these are much more common in US, Australia and elsewhere outside Europe.  (First Response Team of America, Wikimedia(CC BY-SA 3.0)

Are cab-over trucks easier to maintain?

Finally, engine in conventional cab trucks is easier to maintain and fix because it is very easy to reach. However, cab-over trucks do have their own advantages. Cab-over trucks are simply more compact and easier to navigate through tight city traffic.  (Volvo Trucks)