Moving fast through difficult terrain

[coronatiger]

How do I model running through difficult terrain in GURPS, like cluttered backyards, building sites or wrecked buildings? I don't want to spec up every obstacle, but could assign a general difficulty to the area (and the players could reduce the difficulty with Per rolls to find a smart route).

1. How often should I require the players to roll?
2. Which skills should I allow/require? I'm thinking that Climbing, Jumping and Acrobatics are viable options, possibly Running. Are there other skills that could be used?
3. Should I assign different difficulty levels to each skill depending on the type of obstacles?
4. How do I determine how quickly the characters traverse the area?
5. How could familiarity with the terrain reduce time spent and/or difficulty?

Assume an "out-of-combat" situation, and that the total distance will be somewhere between 100 and 1000 meters. (We won't be doing second-by-second action.)