Not sure if I've got this right:
Travelling and hazards, page 135.
"At the start of each shift you drive, you must make a DRIVING roll, modified for terrain type, to avoid a hazard."
If I fail, I roll on the hazard table
I've AGL 'B' and driving 'B' - so pretty good (above average).
For driving tasks, I'll be rolling 2D10, success on 6+, so in practice a 25% chance of failure with no terrain modifier (ie in hills).
On a road at +3, I still need 3+ to succeed, so 4% chance of failure
(And if I enter a new terrain type, I need to make an additional roll)
So if I fail (with a good driver, that's 25% in hills and 4% chance on road), there is a 2 in 10 chance of the vehicle suffering a significant system failure (broken axle or engine blown) that immobilises the vehicle (and which appears to be entirely independent of the reliability rating of the vehicle, or rather the reliability rating of the engine or suspension, since, from the vehicle damage rules these have separate reliability ratings?)
So (again, noting this is a good driver), there is a 5% chance per shift that I drive in the hills that my vehicle is going to be immobilised due to a system having it's reliability reduced to below D.
Seems a bit high, and likely to make vehicle rules almost redundant, since they'll be permanently broken.