the national speed limit on highways unless posted different is 120 kph BUT in most highway tunnels that is reduced to 80 kph for safety reasons. Swiss road tunnels are uniformly in good condition and the entry sign will show how many metres long the tunnel is. You need to reduce your speed before reaching the speed limit sign - either illuminated and variable or painted. Be sure that the lane you are in has a green light, and if the light is red do not enter. Speed limits in and around tunnels is strictly enforced by cameras.
Basel is approached by a number of tunnels and restricted variable speeds - not the easiest place to drive into. Avoid peak travel times but always expect traffic on the approach to Basel,
If you want to drift into France or Germany from the area around Basel expect backups on the approach back to Switzerland, especially on the A5 from Germany. There are lots of signs indicating which lane you need to be in, pay attention and follow them.
If you are returning the car to Basel airport you need to cross the border into France because the airport is actually in France, and there are car returns on both the French side and the Swiss side of the airport and you need to go to the correct one.
