[uticus]

I'm skeptical, if slower == better fuel efficiency, everything else being the same, the owners would drive slower because that would be money in their pocket.

If you're looking for levers to tweak the system, this probably ain't the one.

[zardo]

Aero drag goes with velocity squared, it is absolutely more effecient to reduce speeds.

Drivers are paid by the mile, if you drive faster your effective hourly pay goes up.

[AnthonyMouse]

> Aero drag goes with velocity squared, it is absolutely more effecient to reduce speeds.

It's more complicated than that. Up to highway speeds, energy costs are dominated by mechanical losses like rolling resistance. Meanwhile engine efficiency is higher at particular engine speeds and power outputs, and higher gearing improves efficiency but only if the engine remains in its optimal efficiency range.

This implies there is an optimal speed before aerodynamic losses become dominant, but that speed increases based on various factors like the air viscosity and vehicle aerodynamics. So the optimal speed will be higher at higher altitudes (common in the western US) and higher for vehicles with better aerodynamics.

> Drivers are paid by the mile, if you drive faster your effective hourly pay goes up.

This is another type of efficiency. It does you little good to reduce your fuel costs by $100 if you increase your labor costs by $200.