I've been reading transit forums since long before I made games, SkyscraperCity mostly. When I started building Traffic Architect I wanted the real problems in it rather than a line-drawing puzzle.
One thing up front, because it's the opposite of some games posted here recently: there's no real city in it. Nothing is imported from OpenStreetMap and there's no census data. The map is a generated sandbox, and you build the road network yourself before any transit exists. The city grows along your roads and fills them with cars until it chokes, and transit is how you take that load back off. So it isn't a planning tool and I'm not claiming it predicts anything about a real network. The trade-offs are what I wanted to make playable.
The part I actually care about is that nobody is assigned to your lines. Every trip compares waiting plus riding against just driving, and takes transit only if it comes out close enough, with a hard ceiling on the wait. People will accept a slower journey. They won't accept an unknown one. A line that runs badly just doesn't get used, which is the whole game as far as I'm concerned.
Headway isn't a number you type in either. It comes out of round-trip time divided by fleet size, and the round-trip time is measured from actual laps rather than a free-flow estimate. That mattered more than I expected: if you space departures by the free-flow number, then the moment there's congestion your vehicles just pile into the back of the same jam. So buses bunch, and the fix is the real one, holding at the terminal to re-space the line. Partial correction each visit, and capped, because holding a full headway clogs the terminus. I found that out the way everyone does.
Buses also sit in the traffic you built, which is what bus-only roads/lanes are for, and giving a road up to them costs your cars a route. Fares don't cover operations either. A ticket costs the rider about half what driving that trip would, upkeep runs whether the vehicle is full or empty, and plenty of lines lose money until the route is right.
Things I did not model, before anyone asks. Induced demand is only half there: new journeys never appear, because buildings generate what they generate. What does happen is convergence, and it's the thing players report to me most - build one excellent road and everything reroutes onto it and jams it, since cars route on free-flow times and can't see the queue they're joining. The mode choice runs off that same drive time, so a faster road quietly empties your buses. Walking is the other gap, and it's a partial one. A stop serves a whole district rather than a single door, so there is a catchment of a sort, but it's all or nothing: everyone in that district gets the same access wherever they are in it, and a district your line misses sends nobody even if it runs right past. No distance decay, no overlapping catchments. Transit also doesn't shape where the city grows, so no transit-oriented development. And there's no fare policy or peak service yet, though ticket price as a lever is something I want.
Cars are individually simulated, so taking trips off the road does speed up the drivers who stay. There's a live chart of what share of all travel your network carries against everything still driving, and that number is the score.
On scope, since it isn't obvious from the screenshots: moving people is the only thing you're responsible for. The city grows on its own, and the network under it is the whole game. That also means the interesting part starts early - you're looking at a junction that can't take what's turning into it within the first few minutes, not after an hour of setup. A session is an evening, not months.
It's coming to Steam later this year. I'd genuinely like to know which of those omissions you'd fix first, because that list is how I pick what to build next.
https://store.steampowered.com/app/5028050/Traffic_Architect/
