The differentiator you're probably thinking of is whether the worker chooses which hours they work. If the worker decides independently how much they will work and at what times then the IRS doesn't tend to consider the relationship employment -- regardless of how much time is put in. This is precisely how these driving services operate.

If the employer is scheduling a fixed schedule, say 9-5 M-F, then the IRS considers it an employment arrangement. Regardless of the number of hours worked. But that is not at all how these services operate.