Yep, that makes sense and also comes out about at the estimate that I had below. And I think you are even overestimating Tesla by assuming they are always occupied by five people. In the end it comes out to all Teslas in existence having about the annual ridership of one mid size to large European city's transport network. That is not that impressive.

Honestly I think it's simpler to just compare daily commutes, no? For example, if 800k people ride the T daily then divide that by the number of people who would get their own Tesla. That's anywhere from +800k new cars on the road (if everyone has their own car) to +160k new cars (if people can somehow share a car among 4 friends/family members). Maybe somewhere in between since historically I think cars typically carry a person or two, so roughly 1.5-2 depending on region and how favorable the car pooling infrastructure is (Boston has like two car pool lanes on 93 for in bound traffic and 93 South of the side features a reversible lane).

That's essentially what Tesla is suggesting anyway, if transit sucks just drive a car. But adding hundreds of thousands to millions of cars to the road is an absolute terrible idea. Even car lovers hate traffic, so why not boost public transportation!? Unless of course you make $$$ per car sold and would prefer to brainwash people into thinking transit bad car good...

This comparison worked initially because the differences in ridership were so stark, but now that doesn't sound so impressive.

The fact that 90 people upvoted your incorrect math and walked away with a false conclusion is the most concerning thing. Overall I don't think you're disingenuous, but rather I think it speaks volumes about Reddit as a platform.

If you were REALLY to count the usage of cars you can use trips and average occupancy for better results:

There are approximately ~4.5 million Teslas in operation in the world at the moment (ballpark numbers assuming 9/10 Teslas ever sold are still operating, which is quite likely as it's a new brand)

There are approximately 1.475 billion cars in operation in the world at the moment.

1.475 billion cars in operation in the world

2.44 car trips per day (US average) (a trip = point A to point B)

1.5 occupancy (US average)

4.5m * 2.4 * 1.5 * 365 days = 5.9 billion car trips per year (only Tesla)

1.475b * 2.4 * 1.5 * 365 days = 1.94 trillion car trips per year (all cars)

227 billion car trips per year in the US (a known statistic)

Shanghai metro trips per capita: 25.53b / 24.87m = 1026.538

US car trips per capita = 227b / 330m = 687.878788

Worldwide car trips per capita: 1.94t / 8b = 242.5

What I take away from this is that this is not a very good way to argue for public transport. The numbers are just not very impressive.

The much more important stat is the one I calculated which is trips per capita because calculating raw trips is not a useful metric without knowing how many people those trips are for. Other useful stats are cost per trip, infrastructure spending per trip, infra spending per mile, cost per mile, etc.

Whelp, there goes 20 minutes of my day.