Cutover A/B Street to using osm2lanes

[dabreegster]

osm2lanes is nearly at a point where I'd like to make A/B Street take a dependency on it and remove the original copy of the osm2lanes logic. Just writing down some notes about how to transition, not sure when I'll have time to tackle this.

The steps are probably:

1. Replace is_road, which initially decides which OSM ways to treat as roads in A/B Street
2. Replace get_lane_specs_ltr
3. Import a few maps and manually look for diffs -- I expect to find a few obvious ones, and iterate on osm2lanes or the way A/B Street calls it accordingly
4. After most issues seem fixed, import all maps and do the usual screenshot diff-based validation procedure

• Because the osm2lanes API is still in flux, I'm going to add the git dependency and explicitly pin to a version. It'll be moderate effort to keep A/B Street up-to-date with changes here, so I expect to upgrade osm2lanes in occasional batches
• The biggest missing thing in osm2lanes is width per lane. In the short term, I'll probably just keep https://github.com/a-b-street/abstreet/blob/7fdfdd5e1042a55a7d788ff8470656be9580291b/map_model/src/objects/lane.rs#L495 and do the mapping on the A/B Street side. We'll eventually move this into osm2lanes and handle it properly (reading width tagging from OSM when it's present, using region-specific config)
• A/B Street currently doesn't import footways, or it mangles them into weird cycleways with walkable shoulders: support highway=footway highway=steps highway=path osm2streets#81. Unless I fix that first (unlikely), I'll probably keep transforming things on the A/B Street side to match the current weird behavior.
• For the initial cutover, I'll ignore separator lanes with markings (unless they're barriers), to match A/B Street's current lane types. Things like dashed or solid lines are currently just a rendering concept. Not sure how to properly model those yet.
• Likewise, osm2lanes handles direction for bidirectional and untraversable lanes in a proper way. Some weird corners of A/B Street, like the low-traffic neighborhood "trace around the block" logic, currently depend on sidewalks having a forwards and backwards direction a certain way. I'll post-process the output of osm2lanes in the short-term, and clean up the hack eventually.

[droogmic]

Sounds good,

Replace is_road

This still needs to be implemented in osm2lanes right?

The rest seems relatively clear, cutovers are always challenging...

[dabreegster]

This still needs to be implemented in osm2lanes right?

I just tried the web viewer... plug in https://www.openstreetmap.org/way/39365402, a building, and it rewrote into a road with 2 lanes. So there's the answer. :) If the input doesn't represent something road-like, we should probably bail out cleanly.

is_road has lots of strange A/B Street logic again; we shouldn't preserve that in osm2lanes

[dabreegster]

FYI I started this at https://github.com/a-b-street/abstreet/tree/osm2lanes. https://github.com/a-b-street/abstreet/blob/osm2lanes/raw_map/src/lane_specs.rs has the conversion logic. So far, not bad!

Some of the biggest issues jumping out at me:

1. unimplemented: highway=construction, example https://www.openstreetmap.org/way/663639108
2. Very high width values. Some config based on highway={service, residential, primary} would go a long way
3. unsupported: cycleway:right=opposite_lane, example https://www.openstreetmap.org/way/6287847 (I see a separate cycleway tagged there too... who knows)
4. Loads of errors that occur in practice, like unsupported: more than one bus lanes scheme used, example https://www.openstreetmap.org/way/39817102

I've got enough other things to juggle to help out anytime soon, sorry. :\ But I am working on extracting the logic for making road/intersection polygons into a separate crate, adding unit tests, and taking other steps to make it usable outside of A/B Street

[droogmic]

unimplemented: highway=construction

do you need any metadata associated with this, or is type=construction alone enough?

https://www.openstreetmap.org/way/6287847

I think that is just bad tagging...
https://wiki.openstreetmap.org/wiki/Key:cycleway:right?uselang=en
and the cycleway is tagged separately...
It should be cycleway:right=separate, and be ignored until we have a way of merging these ways.

https://www.openstreetmap.org/way/39817102

fascinating example, so many random tags just thrown together... I think this is where we can start using the Infer<> values to "build" a best guess, and throw warnings whenever there is something suspicious. The error for now should also have been unimplemented, not unsupported.

[dabreegster]

do you need any metadata associated with this, or is type=construction alone enough?

type = construction is nearly enough. I think using construction={residential,cycleway,primary, ...} is useful to feed into the width heuristics though.

I think that is just bad tagging...

100% agree... This is common though. A/B Street needs to do something for broken tagging besides crashing. My approach in the past has been to try to best-guess what the tagger meant, but I think that led to the super messy v1 of the tags_to_lanes implementation. I vote we stay strict in the new osm2lanes. In A/B Street, I can just transform broken roads into something obviously wrong, like a super skinny one-way one lane road, and display some kind of error. If these errors happen frequently in areas I personally need for other work, I'll pre-process tags on my end to "fix" them or attempt to fix upstream in OSM.

So... osm2lanes should stay strict.

I think this is where we can start using the Infer<> values to "build" a best guess

Same as above -- I have no idea what the mappers meant here. :D I'd honestly be happy just quasi-refusing to attempt to render this in A/B Street going forward, to encourage cleaning up the tagging. Handling the best guess in osm2lanes is an option, but

1. I would vote that complexity stays cleanly separated from the rest of the codebase, something like tags_to_lanes/repair/bus.rs
2. I wouldn't prioritize working on these inferences over handling more "correct" tagging

[droogmic]

Do you need an is_road clone,

or can you do:
Highway::from_tags(&tags).is_supported()?

[droogmic]

my next 2 PRs, in no particular order:

• move to a RoadBuilder API internally to do full roundtrip.
• lifecycle support

[dabreegster]

I can use Highway::from_tags(&tags).is_supported(). I suspect I'll keep some of the weird filtering and transformation of is_road in the short-term, or move it just after this method.

[droogmic]

so construction is now in, where do we stand?

[dabreegster]

I will revisit after March 23, sorry :( Very high-stakes conference / deadline to finish the LTN work

[droogmic]

(reminder)

[dabreegster]

I did not get less busy yet. :(

But when I revive this, I'll use it as a forcing function to start some kind of locale-specific width config to roughly match areas I've spent a little time tuning before.

[droogmic]

Ah, width is missing.
I am mainly using this to prioritise my efforts, because at this point the only thing I really see left to do is to iterate through tests cases trying to turn them all on.

[dabreegster]

Ah, yeah. Biggest missing thing from my POV is width. And if we wind up with a public API sort of like https://github.com/a-b-street/abstreet/blob/191f1ca265a51563995460f5375913ed30f7895a/raw_map/src/types.rs#L472 (but with locale, highway type, and lane type as input), even better, because then A/B Street's lane editor UI will just automagically make more sense in different places.

[droogmic]

I think the latest version will improve things, I haven't set up a dev environment for abstreet yet to check myself though, will do that ASAP

[dabreegster]

I'll update the draft PR with latest osm2lanes real quick. I don't think I can work on validation for a bit, though.