[Talk-GB] Modal Filters and Low Traffic Neighbourhoods

Steven Hirschorn steven.hirschorn at gmail.com
Sat Apr 10 08:04:09 UTC 2021


Hi All,

Sorry, long email as there's a lot of complications here that I've been
wondering about for a few months. I did a Google Search of the archive and
I don't think this has been asked before. Another volunteer and I have been
updating OpenStreetMap to include the new modal filters introduced as part
of the government's active travel policy.

If you want to see what the ones I've been mapping look like today in real
life, I've added imagery to Mapillary, and there's an example here:
https://www.mapillary.com/app/?lat=51.50207919997222&lng=-0.32299659999999997&z=17&pKey=n99sCMMhsDCVfS8jBIuNQE&focus=photo

I wanted to get advice on the best way to map them? The task is partly
complicated because in Ealing many of them have been implemented diagonally
across junctions, turning them effectively into turn restrictions. When
originally installed, they had a removable bollard in the middle, but this
has been permanently removed to facilitate better emergency services access
and to allow disabled driver (blue badge) and a small number of other
exemptions. They are now mostly enforced by ANPR cameras.

Generally, the way people have mapped them is to split the roads at the
crossroads, joining them to make two corners highlighting the turns, and
then adding a highway=cycleway in between to facilitate routing. Sometimes
tags have been added for emergency=yes, horse=yes, motor_vehicle=no,
foot=yes, and I'm not completely clear which ones are superfluous.

I know we don't tag for the renderer, but one aspect I like in the way
others have mapped them is that it makes the OpenStreetMap default
rendering really clear about where the filters are and which route a driver
would need to take to get to any address in the LTN, something Google and
here.com (for example) aren't coping with very well at all. It also worked
very well for the routers and OpenStreetMap based routers have been correct
from day one unlike Google which still sometimes offers routes that are
illegal (try finding a logical way to submit a diagonal filter to Google
Maps!)

What I don't like is that if I now do an Overpass query for cycleways,
there are lots of 2 metre long "cycleways" dotted all over the map. Also
I'm not sure if highway=cycleway & emergency=yes (because ambulances and
fire engines are allowed to pass) is a valid combination? And is there a
way of mapping that there are exemptions for blue badge holders? I know a
lot of this is moot as the ambulance service use old sat navs that AFAIK
aren't aware of emergency service exemptions, but the principle of having
an emergency service route option as well as "car", "bicycle" and "foot"
seems like a brilliant concept)

They could alternatively be mapped as turn restrictions, but I don't think
it's possible to make an exception for bikes, and turn restrictions
wouldn't be visible on the map rendering.

I noticed that a user, MacLondon, has added an extra tag "note:covid19"
tags (with value "Experimental modal filter") which makes it a bit easier
to query for the new filters if anyone wants to look for more.

What do other volunteers think?

Steven
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