The theoretical maximum would be all vehicles operating at highway speed limits of perhaps 70MPH, non-stop through all points, bumper to bumper, packed as dense

The theoretical maximum would be all vehicles operating at highway speed limits of perhaps 70MPH, non-stop through all points, bumper to bumper, packed as densely as possible, according to a profile for vehicular mixture, achieving was is effectively the equivalent of laminar flow for fluid dynamics. If everything is tractor trailers, the throughput is lower based on vehicle classification. If everything is passenger cars, variation between SUV and sub-compact car provides a mid-range. If everything is motocycles only the vehicle dynamic squashes vehicle volume and boosts maneuverability to inflate apparent throughput. Somewhere in this, driver skill level and physical fitness comes into play though, so there has to be an index for that also, based on available residential zones, and an origin/destination matrix. If everyone is driving from the retirement home to church bingo, the throughput will be lower than tractor trailers. Tractor trailers and other commercial vehicles are expected to operate at lower speeds due to inertial lag during braking and acceleration, prolonging periods spend at lower speeds. All other vehicles can only be modeled according to legal speed limits, even though the accuracy of the simulation is threatened by the fact that in reality many vehicles will be ignoring speed limits. Time of day, however, is usually going to model rush hour, which consequentially alters vehicle profile and driver persona.