- a lot of it is probablility-based/spontaneous; only some traffic patterns are regular (children to school); to service the probability-need, you need a regular service that may run empty/low half of the time, until people need a hair-cut.
The whole thing is handled on a sliding-scale/spectrum, ordered by how short/far into the future, the travel is/can be planned. On one end, you have taxi/uber, which is on-the-spot travel. The other end is planned year-service, e.g. a summer schedule of a bus. In between, with computers we have a lot of "urgent-but-planned" flexi-flexible traffic, where people book on the day or the week, and a number of bookings are then weaved to be driven like a pearl string (so e.g. a number of people will share a ride in a medium sized bus, that does pre-planned pseudo-taxi-service.)
Of course, as you say in the OP, one can certainly encourage the public to use simulations based on publicly made-available data as a guide during these political discussions to convince people that a certain metric is better than others.
There is a reason why a lot of american bus networks basically follow the same old streetcar routes that were always there. People become used to existing patterns and build lives around them. New transit is a good opportunity to apply this model, but reworking old transit is tricky because some of your existing ridership will end up with a worse offering by definition, and they will protest. While the people who might benefit will not show up with equivocal advocacy in the public comment meeting.
By building in the capability to stop very frequently, they can serve the most people and every area in the route, equally. But day to day, hour to hour, they are definintely bypassing stops, and I can name at least 3 bus routes where the vehicle will certainly reach the speed limit of 45mph or so in-between.
I've noticed that there are some diversions which are definitely beneficial to me. There are busses from my house to the city center, as well as a tram. If the tram diverts to a different destination that essentially doubles my available "travel destinations" in a way that's really useful.
So no doubt, for me personally, there are changes that could be useful. But perhaps they would be less useful for others.
A lot of people commute for hours to sit at a computer...which means they could work at home.
I don't remember the terms used, but I've seen data sets of where people live and work in Manhattan, and you do see people who live on subway lines take jobs on that same line, and they don't take jobs on a different subway line that while possible is overly inconvenient.
people have already arranged their life around the existing transportation that exists around them. They are not going to change their life because it is already in place. They want bottlenecks fixed but otherwise don't really need a change to their life. Even if a change would greatly benefit them, they often can't see that and wouldn't imagine themselves making the change to their comfortable life.
The real value of transportation experts is they can look at a map and all your data and say, if we make these changes, over 20 years, the city will redevelop in this way, and then we can ask questions. "Is that how we want the city to develop?" however, the data is never going to show that because the data shows what people are doing today, not what they're going to do in 20 years. Don't get me wrong, experts get this wrong too when they make predictions. However, there is a lot of things we can use to inform our predictions. even though we're not perfect, we can make predictions that are usually right.
Varying the route timing is the absolute worst thing you can do. People need to depend on your transport system. If they have to look at a schedule that's going to change by day to figure out when they can actually get somewhere, they're going to get frustrated and start looking up for an alternative that they control. If you vary your timing at all, it's only because you're changing between a train every minute to train every five minutes. You don't get to go any farther apart than that without losing writers because they no longer can trust that the system will get them there when they want to be there. Physics puts a lower limit on time. I believe the current record is a train every 90 seconds, and I'm not sure how much closer together you can get. The limit for a bus is three minutes apart and even that is extremely hard.
Transit systems that are running worse than 5 minute frequencies have large drops in ridership and as they increase frequency: ridership jumps because people start to use, they can always just go out when they're ready to go. If this wasn't so expensive, everyone in the world would be running 5-minute frequencies all day.
It sorta works for going into the nearish big city for a 9-5 event. But it’s worthless for the evening because of infrequent trains.
The question that we cannot answer for Manhattan data is what if Manhattan added a few North South lines or I can think of hundreds of different things that Manhattan could do. I don't live there and I haven't studied the data in depth so I couldn't tell you what is a good useful thing for Manhattan to do. But I can tell you that there are lines that would over the next few decades greatly change how people in Manhattan and the rest of the city live. Unfortunately, Manhattan is particularly bad about the costs and so they can't even afford to remove the obvious bottlenecks much less a whole new line that would over time be make the city much better.