Eliminating extra traffic reduces the amount of wear-and-tear on a street, which means you can go more years without resurfacing or replacing it. So even if you still need all of the roads, they could still cost significantly less to maintain.
That said, I'm not really sure how the math works: delivery trucks and buses are a smaller number of the vehicles on the road, but they also weigh a lot more than cars. Some DOT probably has a chart somewhere which breaks down road wear by vehicle type.
> Eliminating extra traffic reduces the amount of wear-and-tear on a street, which means you can go more years without resurfacing or replacing it.
The standard argument is that wear goes up either exponentially (which seems wrong) or quadratically (seems more reasonable) with vehicle weight. Since heavy vehicle use will actually go up (more delivery) if we eliminate cars....
I've seen how other activities, tearing up streets for utilities and the like, which are surprisingly common in cities, lead to street repair. Those activities won't change if cars are eliminated.
Parking garages will go away, and major streets could be narrower. I doubt that either effect is significant compared to the road costs which have been claimed to be huge.
Nref = Nx (Wx / Wref)^4
Nref = number of trips of reference vehicle
Nx = number of trips of other vehicle
Wref = weight of reference vehicle
Wx = weight of other vehicle
The quartic formula really works in our favor for bicycle commuting: if a bicycle (with rider) is 1/20th the weight of a car, the bicycle will produce 0.000625% the wear of the car. So if commuting were the only purpose of the road, you would essentially never need to replace a road again.
This does make adding (larger) delivery vehicles quite bad. If the average delivery vehicle is twice as heavy as the average passenger car which was formerly used, each trip will produce 16 times as much wear. Looking up the curb weights for a Chevy cargo van (5000 lb) and a Toyota Corolla (2800 lb), the actual wear factor is 10x.
That said, I'm not really sure how the math works: delivery trucks and buses are a smaller number of the vehicles on the road, but they also weigh a lot more than cars. Some DOT probably has a chart somewhere which breaks down road wear by vehicle type.