In Bloomberg CityLab's article, “NYC’s Shadow Transit Network Seeks a Greener Future,” Director of Transportation, Eric Goldwyn, is mentioned:
[Goldwyn’s] 2020 paper "Anatomy of a New Dollar Van Route" explored the inner workings of this mode, says that service frequency is the dollar vans’ "magic sauce." On popular routes during rush hour, he’s watched dollar vans stream by at a rate of one per minute. Tech-era microtransit services that try to accomplish similar feats generally can’t replicate the regularity and quick headways of the dollar vans. Operators also have the flexibility to shift routes on the fly, unlike the buses of the MTA, which can’t drop a stop or tweak a schedule without studies and public meetings.