So far as I know (I haven't ridden it in a few years), CalTrain doesn't have frequent enough service to make schedules irrelevant. [I don't know the generally

So far as I know (I haven't ridden it in a few years), CalTrain doesn't have frequent enough service to make schedules irrelevant. [I don't know the generally accepted figure, but I'd say anything with headways of greater than 10 minutes or so is not suitable for just-turn-up-and-go usage.] Obviously frequent service is good, but there's a large variety of lines and sometimes very frequent service isn't warranted (or isn't possible because of funding/politics/etc). For a line with non-frequent service, "just look at your smartphone" isn't a good solution, as (1) not everybody has a smartphone available, so it's a bad idea to make a transit service that requires one for decent service, and (2) more importantly, in many cases with less frequent lines not being able to plan can be a significant burden, especially when you need to make transfers along the way (in which case you always have to assume the worst case, and all the required uncertainty padding quickly adds up). So for user convenience either you want frequent service, so planning isn't needed, or you want scheduling that's at least a little accurate, so planning is possible when necessary. [There are also technical reasons for scheduling even very frequent trains in some cases, because when trains become frequent enough, the line itself can become a bottleneck, especially with complex services. For instance on many lines in Tokyo, both ordinary, express, and limited-express trains share the same tracks, with the expresses using in-station bypass tracks to overtake the non-expresses. The track network is also in many cases very non-linear, with many different lines sharing portions of tracks in some places, and different operators running onto each others' tracks. To do all this with high frequency services requires a delicate timing dance, and if you screw up the timing beyond some point, the whole thing very quickly falls apart.]