Weeelllll...first up, good on you for being so bold as to engage one of the most flaky, number-crunchy and potentially confusing aspects of Shadowrun.
I do a lot of "Area type encounters" like you do, since one factor I cannot reliably control is the route and actions the players will take.
A few "rules" I adhere to:
-Glitches on a driving test always trigger an appropriately dire (or comedic) response., relative to their zone. These may have unexpectedly beneficial consequences.
(a chase through Seattle's storm drain system ended with my players slipping away from enemy thugs, due to pissing off a major ghoul nest)
-Track the player's vehicle's damage and speed carefully (NPCs'), since penalties to driving apply to any attempts at avoiding/mitigating a crash.
-Slipping a tail becomes INFINITELY EASIER when there's no aerial or drone support. Conversely, the players should have a hard time getting off the drag net.
-Remember who is chasing whom, and who may respond in kind, with or without the players' provocation.
-With the right spells, a mage can end most chase scenes immediately with little effort. I will emphasize that this can work both ways.
\-On a related note, "geek the mage first" is noticeably trickier when you can't easily spot him. Most vehicles provide cover, and it only takes but a moment for a mage popping up to work their mojo.
-Even after a chase is over, remember the condition of the vehicle. Unless they're rolling around the Seattle Barrens or somewhere equally unpleasant, people are going to notice the scorch marks and bullet holes in your runners' ride.
