[joshjob42]

Where do you get 30 drivers per 100 vehicles from?

Let's model it as every takeover is 1 min, and vehicles need help 5% of minutes. Then you'd model the # of vehicles needing help in any given minute as a binomial distribution with p=0.05 and N=100, and you find you get 99.99% of the time you need less than 15 drivers per 100 vehicles. By 20 drivers, you cover all but 2e-8 of the time (or once per century).

But that's a bit misleading. It's a small-size effect. With 10k cars, you get cover all but 4e-6 of all minute periods with just 600 drivers (0.06 per car).

By 100k cars, you have 44 9s of reliability with 0.06 drivers per car.

There's some more complicated things that arise since probably the distribution of how long vehicles need help will be Poisson distributed (with an average of 1min) most likley, etc. But the point will stand, for large fleets you only need a modest margin over the average rate to get effectively complete coverage under normal conditions. It would only be in really extreme situations, like a hurricane messing up badly a lot of the Eastern seaboard or something, that you'd maybe run into issues (which, admittedly, is a real potential problem).