[ProfessorLayton]

Funny you say that because most of my Uber/Lyfts consist of me going to and from public transit for my intended destination.

Although it is more complicated than that, as I often take a shared ride home because Bart shuts down too early on weekends to be useful on the way back.

Additionally the math gets complicated when I have multiple people with me, as often times it's cheaper to uber/lyft somewhere to our destination than it is for all of us to individually pay for a Bart ticket.

[matt4077]

This is called multimodal transport. I'm unsure how big the effect is for Uber/Lyft where booking the ride would seem slightly more involved than, say, using a bike. But it's an area of great interest especially for public transit planners.

[rdiddly]

I'm only comparing what happens in the world we have, where Uber & Lyft exist, vs. what would happen if they didn't, or would've happened back when they didn't. Obviously some of this is guesswork kind of like "Gee what would've happened if I'd married my high school crush" or whatnot. But in general if you would've walked or biked to transit before, and now you take Uber & Lyft, that makes congestion worse. If you would have driven to transit, using Uber/Lyft has no effect. If you would have driven the whole way, it's a partial improvement (by riding transit for that one segment).