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Comment by Flux159 | Hacker News Reader

I like the idea as its an interesting map visualization of the subway across a time domain rather than distance.

I'm wondering why there's such a large difference in certain areas between weekday rush hour and late night though (for instance, clicking on 68th St Hunter College and changing between weekday rush hour and weekday late night is making 59th street go from 2 mins away to 12 mins away).

A few notes about mobile (specifically iPhone usage): Its difficult to use on iPhone because the first tap doesn't seem to do anything to the map - if you tap again at exactly the right place (on the dot), then it will work on iPhone. I think I know what the issue with this is: the onclick event is being replaced with the hover state when you tap once, then the real onclick is called when you tap on the dot again.

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> I'm wondering why there's such a large difference in certain areas between weekday rush hour and late night though (for instance, clicking on 68th St Hunter College and changing between weekday rush hour and weekday late night is making 59th street go from 2 mins away to 12 mins away).

Fewer 6 trains, I'm guessing - they come roughly every 3 minutes during rush hour (and the trains are still crowded) but that wait time goes way up late at night (that delay goes all the way uptown on local stops past 59th st).

What I'm not certain about is why the delay isn't nearly as different between local stops below 59th st.

I'm calculating travel times by simulating a rider starting from the selected stop at a specific time (for example, "weekday late night" is 3 AM, and "rush hour" is 8 AM) and "waiting" for he next scheduled train. That's why, when you select most stops during late night, the nearest stops are pretty far (~ 10 minutes) away — because that's a typical time you'd wait for a train at that time of night. It's definitely not a perfect prediction.

And yep — I really need to put some work into the mobile experience. I'm surprised it works at all!

To address that issue, a better calculation might be to compute possible wait times based on distribution of likely arrival times at the station and return some weighted average.

The issue with using average waiting times (as opposed to picking a particular time and computing actual waiting times) is stations with multiple trains — the N, R and Q might each stop at Union Square once every 10 minutes, but if you're happy boarding any of those, then your average wait time isn't 5 minutes — it's much less.

What I might try is sampling a couple random start times (e.g. 8:00 AM, 8:03 AM, 8:22 AM) and averaging the predictions of all those.

> What I might try is sampling a couple random start times

My gut says this would be a better value, but I don’t have the evidence to prove it

Going from some stations to stations on other lines, it takes more time to get to the transfer station than to several stops farther on the second line. That seems off.

Choose Rockefeller Center then look at the purple line just below it for example.

My guess is they add the average wait time to the travel time. That would match my expectations for a 6 train. They're about 3 mins apart during weekdays. Not sure what that particular train is like at 3am, but I've seen other trains with 20+ minute wait times.

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