Does anyone know the actual equation or formula used in Fallout 2 engine for calculating whether an encounter can be avoided?
I've found resources saying it's a roll against Outdoorsman and the Motion Sensor gives a +20% to the roll, but not much more detail than that.
I'm pretty sure Per Jorner wrote something about this, but his Fallout Guide seems to be down.
Anyway, from my own experience I think it works something like this...
The game takes your Outdoorsman skill (or a party member if any of theirs is higher), adds + 20 to that if you have the motion sensor (will add the bonus to a party member even if it's in your back pack). The sum will be capped off at 95 if the total exceeds that. Then it will subtract the encounter difficulty (between 0 and 70 depending on map tile), and what is left is your chance to avoid an encounter.
I'm sure you already know the following bit, but just to be clear.

If you look in WORLDMAP.TXT you can see that the world map is divided into 20 tiles (each containing 42 map squares). At the top of each tile section you will find the 'encounter_difficulty' for that set of map squares.
So let's say you have Outdoorsman at 95 (with or without the motion sensor) and you are running around in a tile with an encounter difficulty of 0, you will have a 95% chance to avoid trouble. If you are in the toughest areas however (difficulty 70), you will only have a 25% chance to skip the encounter. The Outdoorsman skill (+ motion sensor) obviously has to be higher than the encounter difficulty, or there is no chance at all.
Your trusty old car also comes with it's own built in encounter skipping system. But unfortunately for you it only works half the time. So if you are driving around in the car and you first fail the Outdoorsman check, the car will do a 50/50 roll (not a skill check), and if you pass, you can skip the encounter.
Also, you get experience points for avoiding an encounter with the help of your Outdoorsman skill, but you get none from the car check. I suppose the logic is that it takes no skill to just put your foot down and accelerate away. Either that or the devs just forgot the XP (It's not like that kind of thing hasn't happened before).
