It's obvious from the comments on this thread that most posters either don't already know or haven't seen the various videos on You Tube relating to SAC procedures, or the more recent ones showing B-52H and KC-135R Minimum Interval Take Off (MITO) scramble procedures - so I'll go ahead and find them again.
Only the B-52H remains in service which has a 5-main crew as the there is no tail gunner.
The routine method of starting a B-52H using AGE normally takes about an hour:
For MITO scrambles, crew arrival at the aircraft to take-off can be achieved in about 10 minutes using the he cartridge starting system:
https://www.af.mil/News/Article-Disp...20the%20B%2D52.
Declassified SAC films indicate that the normal readiness state of Alert Force aircraft (both bombers and tankers) was RS15 - so that leaves around 5 minutes to get from the Alert Force building to the aircraft.
Alert Force vehicles in the SAC era were dedicated to each crew, self-driven, fitted with flashing lights and sirens, designator signs, and where necessary there were priority routes controlled by traffic lights.
Various videos shows Jeeps (1950s with the B-47), station wagons (estate cars) in the early 1960s, crew cab 5-PAX pick up trucks from the late-1960s, and most recently a mixed bag of unmarked commercial colored Ford Transit minibuses, pick up trucks and minivans with magnetic designator signs.
The main reason for MITO scramble practices now is to maintain the ability to Survival Scramble aircraft in the event of ICBM / SLBM attack. From the mid-1980s, numerous papers have described how the ability to get airborne in time is marginal - particularly in the face of a low trajectory SLBM attack.
These KC-135R crews are pretty sharp: