I’m involved in a similar project in Germany (https://safer.uni-wuppertal.de/de/), and I can confirm most of what you wrote. We are also struggeling with incomplete pedestrian OSM data.

What I miss, in addition to the lists you gave above, are the entrances of schools. We found that the position at which children enter the school grounds has a significant impact on school routing.

Crossings are also very important. We found that around 80% of accidents involving children (ISCED level 1) on their way to school occur at crossings. There are several reasons why I prefer to map footways separately. One reason is that crossings are rarely forgotten.

I haven’t thought about traffic calming elements yet. This is a good idea that we should use too. Thanks for mentioning it.

First of all, there is the question, what qualifies as a crossing. It’s easy whenever there are markings or traffic lights. But all the crossings without markings are often difficult to spot: Lowered kerbs? Tactil paving? Island? Is one of that enough to qualify a place for a crossing. And what, if a lot of people cross at that place, but there is nothing visible on the ground? Does this still qualify as a crossing?

What’s next, is the problem with separately mapped sidewalks: In this case, for working pedestrian routing you need crossings at every place, where the street forks or cross. (And the other way round: In the case of attached sidewalks, people assume, that crossing is possible at every place, and there is no way to map if it is actually not possible.)

And: In my oppinion: If one maps a crossing, the main tag ‘highway=crossing’ should always be added. (Some people omit this, when they think, the crossing does not qualify enough for a full crossing, but do not want to map nothing there.)

@sosquqer: It’s a rather complex theme and I do not understand every aspect, too; probably no one does. That said, I’ll try to explain, what I do understand:

• Essentially, there are two ways of mapping sidewalks: as tags on the roads or as separate ways. Currently, there is no agreement on which is better. From my perception currently most mappers prefer separately mapped ways on larger streets and tagged sidewalks on smaller roads. (This is not my opinion, I prefer separate tagged sidewalks on all roads.)
• If you map a sidewalk separately and do not add a tag on the main road, users of StreetComplete will be asked, if the street has got sidewalks. They will answer yes and then you’ve got both: Tagged and separate sidewalks. Hence the value separate. StreetComplete now knows, there is a sidewalk, and will not ask. (Same is true for other applications.)
• Pedestrian routers need to use routing in the middle of the street, whenever separately mapped sidewalks are missing. They even have to do this, when there is no information at all, assuming, that it is just not mapped yet. Without such assumptions pedestrian routing is not possible. (It would be possible if most sidewalks had been mapped.) If the streets contain no information whether there is a sidewalk separately mapped, such routers might use the middle of the street routing on such streets despite a separately mapped sidewalk being there (for example, because it’s shorter).

@sosquqer: I actually prefer highway=footway + footway=sidewalk over any attached solution.

Why didn’t I count them then? Well, while it is possible to count the mapped sidewalks it is not possible to count the ones, which have not been mapped. But for knowing a percentage, I need this second value too. That’s all.

Additionally: The highway they belong to, should have one of the sidewalk-tags with value separate. So in a way, they are still counted.

@Niquarl: Thanks for pointing me to Sidewalker. I didn’t know about it. Good tool!

Thanks for pointing me to OpenStreetBrowser.org. I didn’t know about this tool.

Concerning “obvious” defaults: I think, in rural areas I would fall in this trap too. Roland goes even further in his speach: He ignores residential roads on purpose, because the sidewalks there are “unimportant”, which leaves more time to do the main roads. For me, this doesn’t feel right. I’d prefer to complete an area at once.

@InfosReseaux: Thanks for pointing me to your blog post and indirectly to data items. I didn’t know about them. On first sight, this sounds like a very good idea. :-)

In general, uncertainty is often a problem, which prevents changes. Fears are very strong. And too much disruption isn’t healthy anyway. But no change at all is probably even worse. That’s what I tried to express in my post: Always do some steps, probably small steps, but don’t stop.