Add bus and rail POIs for stops and stations

[Pengor]

Description

This adds bus stops/stations and rail (including subway and tram) stops/stations. I think there are a lot of directions we could go with the design of the icons for public transportation but a simple head-on view of a bus and a train made sense to me as being both recognizable and consistent with iconography used by various transportation agencies.

I tried to keep the two icons differentiated enough to be recognizable, but the nature of them both being head-on views of a larger vehicle makes them inherently look rather similar.

In the future I could see additional icons for trams/streetcars and subways, but in many places in North America the distinction between light rail, subways, and trams isn't always crystal clear to those unfamiliar with a transit system, so I don't think it's necessary at this point in time. If we eventually have clickable POIs then that info could alternatively be surfaced at that point.

Addresses #436 and #790.

I went with making these appear starting at z16 as the density of bus stops and train stations is approximately equivalent to the density of cafe and bar POIs in downtown areas I referenced while working on this (Seattle and NYC).

Renders

Before (1x display density):

After (1x display density):

Before (2x display density):

After (2x display density):

Fun fact: Third Avenue in Seattle (shown in these renders) is supposedly the busiest bus corridor in North America!

[claysmalley]

We'll need to find a way to stylistically distinguish stations from stops in both bus and railway features. OsmAnd does this by giving stations (e.g. bus stations, light rail stations, train stations) circular icons, and stops (e.g. bus stops, tram stops) square icons.

I think the bus icon is fine as it is, and we could adopt a similar backgroundless style for tram stops. But I'd like to see bus stations visually distinguished somehow, perhaps with a circle background, and we can apply that same visual element to railway stations.

[wmisener]

I agree that this would be a good feature (unsurprisingly, since I mentioned a similar tack in https://github.com/ZeLonewolf/openstreetmap-americana/issues/790#issuecomment-1475432421).

[Pengor]

I think this makes sense, I've drawn up some circle-enclosed icons and will commit these alongside changes to render icons by subclass instead of class:

[Pengor]

Fixed in 8b7012b

[wmisener]

Thanks for putting this together! I think the icons are nice: those bus headlights are quite stylish, and while I think down the road it would be best to distinguish light rail, subways, and conventional rail, this icon is nicely ambiguous for the time being IMO.

My first impression from your screenshots is that the bus icons seem quite large. They have a lot of visual weight in my eyes, which I'm not sure matches their importance (and this comes from someone who takes the bus every day to work!). I wonder if it would be better if the bus icons were smaller than 20x20px, so they'd be smaller than the cafes and whatnot. I'm not sure this style has ever done that before so maybe that needs some discussion as a general stylistic choice. I think train stations can stay the same size as they are, though as Clay suggested it might be good to distinguish tram stops from other stations by inscribing the icon in a circle for stations.

[Pengor]

Updated now that separate POI icons can be rendered by subclass. There are icons for bus and rail stations enclosed in a circle. I think these are sufficiently different looking from one another but happy to incorporate additional feedback!

Examples

Light rail stations, bus stops, and streetcar stops:

Bus station and light rail station:

Bus station and bus stops:

[claysmalley]

Looking pretty good altogether.

Just a nitpick—I think the bus and tram icons would look a little better if they were shrunk to match the size of the inner part of the station icons. Otherwise the stops kind of visually dominate the stations, the opposite of what I'd expect.

[Pengor]

Shrank the "stop" icons for bus and rail to match the size of the inner parts of the circular icons:

[claysmalley]

Looks good to me!