The wiki page on transport in Switzerland has a map which shows the A2 as a motorway running between Lucerne and Bellinzona and beyond. One conclusion that a highway engineer might reach is that, as this section of road is a motorway then the design speed and the posted speed limit will both be 120 km/hr or above.
In fact, both design speed and speed limit on motorways are frequently much lower than 120 km/hr; for example, the posted speed limit is typically 80 km/hr in the section of the A2 which forms the northern approach to the Gotthard road tunnel.
Because of the local geography (steep mountains), designing this part ofthe A2 for a 120 km/hr speed limit would likely be prohibitively expensive. But this is a decision based on considerations of cost (how much are we prepared to pay?) and not on anything to do with road classification or engineering design parameters.
All this raises some questions. For example
- From what speed limit does a motorway stop being a motorway and become a normal road? (e.g. is a dual carriageway with grade-separated junctions and a design speed of 60 km/hr a motorway or an urban expressway?
- If a road with a speed limit of 80 km/hr is a motorway, why not design all motorways to a speed limit of 80 km/hr? That could save more money.
- Maybe there should be different sub-classes of motorway, such as
- Class A (speed limit of 120 km/hr)
- Class B (speed limit of 120 km/hr, no emergency lanes)
- Class C (speed limit of 80 km/hr)