QUOTE (Blade @ Mar 16 2016, 12:31 PM)

They were indeed response time in combat turns in some 2nd ed book (Corporate Security Handbook? Lone Star?). The idea was that if it took more than a few combat turns, the PC will already be far away.
Response time will obviously vary a lot from one place to another. Generally speaking it will be quite different from today since:
- You can have many drones on stand by in different places that you can quickly dispatch to a nearby area.
- Spirits and astrally projecting mages can be on the scene in a matter of seconds.
- A spider/security hacker can access the nearby devices, this can be security cameras (and being a private company means that LS/KE can have contracts with stores/businesses which means they can access all the cameras from these places as well) but this can also be anything that will let the hacker/spider gather information about the runners from all the wireless enabled things they are carrying and track them from the Matrix.
- A VTOL can bring reinforcement faster than a patrol car or armored van.
- The multiplication of private security companies can either make it better or worse for the runners. Better because LS/KE might be slowed down by the local security contractors, worse because the local security contractors can be more efficient and responsive than a police force with resources stretched over the whole plex.
- Service can be totally cut in some areas and/or at some times because having a police coverage there at that time has been judged too costly.
Also finally, you have to remember that in many cases, runners are not just regular burglars/gangers. Even in a world where a drugged-up cybered ganger can shrug off a storm of bullets. This means that when it's clear that the bad guys on site are runners (with heavy cyber/powerful magic/military grade weapons and drones/etc.) the police might not just send one more patrol car, but might want to evacuate the area and bring in the choppers, drones, mages and spirits, some SWAT teams, etc. (or send only one heavily modified veteran with an armada of camera drones streaming live to the trid).
Of course, this will depend on how dangerous the situation is, what other stuff are currently happening and how efficient you want LS/KE to be in your setting.
So all in all, I'd say that the setting allow for about any kind of response time, from being swarmed by drones and spirits in a few seconds to nobody caring about it ever. It just depends on the conditions and what's most interesting in your game.
With the number of potential holes, it feels like there should be a roll involved. A glitch means there is poor coverage or security was routed incorrectly, and a critical glitch means it's "someone else's" coverage area.
Assigning 1 die for D zones, and adding one for each level better would give the weirdness with 2 dice being the worst possible. Maybe do 1 die for Z zones, but also require a good reason and at least one hit? They'd have to be focused to go into a Z zone (not just relying on local cameras, drones, and patrols - they aren't present to rely on), so they'd be less likely to screw up if they did so. But it would happen less often.