Your formula is incorrect; time is more of a factor than mileage, when it comes to vehicle deterioration. This is why you routinely see taxis with more than 300

Your formula is incorrect; time is more of a factor than mileage, when it comes to vehicle deterioration. This is why you routinely see taxis with more than 300,000 miles on their engines. Furthermore, automation itself will reduce wear-and-tear. I worked on the driverless pod system at Heathrow Terminal 5. One of the things we found was that wear-and-tear on the system was almost negligible -- probably less than 10% of what you would see in a human-driven vehicle. This was partially due to the fact that it was driving on a smoother surface than an ordinary roadway -- but also due to the extremely conservative and consistent acceleration/braking behaviour which the vehicles achieved, which put much less stress on many parts of the system. Although those are essentially hand-built prototype vehicles, I expect them to last ~400,000 miles before requiring significant refurbishment. Based on these observations,I feel quite comfortable predicting a dramatic decline in the rate of vehicle sales within the next several decades.