[Talk-GB] Modal Filters and Low Traffic Neighbourhoods

Sat Apr 10 21:41:00 UTC 2021

Hi all,
This is my previous thread on the topic:
http://gis.19327.n8.nabble.com/Tagging-modal-filters-and-school-streets-td5975146.html#a5976006

Since then I've added rather a lot of these to the map:
https://overpass-turbo.eu/s/15YS

I know its not approved, but the tagging scheme I'm using is working out well:

-----
The traffic_intervention tag is used to identify locations where roads
have been closed to general traffic for the purpose of preventing
undesirable through traffic.

The traffic_calming tag covers many use cases where the road is open
but something physical has been added to slow down traffic. Sometimes
however, the local traffic authority goes further and closes a road to
through traffic - traffic_intervention is used to record these
interventions. Mappers should ensure that all normal tags are still
applied to the relevant road segment, traffic_intervention is intended
to be used in addition to existing tags to capture the semantic
meaning.

traffic_intervention=modal_filter
A modal filter is a road closure that is designed to allow certain
modes of transport through, typically bicycles and pedestrians. It is
intended for short sections of road that used to be open to general
traffic and are no longer. The standard modal filter that allows
cycles should be mapped as follows:
* A way representing the section of road that is closed to general traffic:
highway=cycleway, traffic_intervention=modal_filter, other tags as
necessary, especially including the road name.
* A barrier in the middle of the way representing what is being used
to close the road. For example:
barrier=bollard, foot=yes, bicycle=yes

traffic_intervention=bus_gate
A bus gate is a short section of road that has been closed to general
traffic but is open to buses, bicycles and pedestrians. It should be
mapped as a bus road would be, but with the additional
traffic_intervention tag.
* A way representing the section of road that is closed to general traffic:
highway=service, bus=yes, bicycle=yes, foot=yes, traffic_intervention=bus_gate

traffic_intervention=school_street
A school street is a section of road near a school that is closed to
general traffic, often only at certain times of day. The access
restrictions are normally mapped using motor_vehicle:conditional.
Simply use traffic_intervention=school_street to add the additional
semantic meaning.

Mappers may additionally specify the year, month or full date when the
road was restricted if known:
traffic_intervention:date=<year>
traffic_intervention:date=<year-month>
traffic_intervention:date=<year-month-day>

Mappers may refer to the traffic order in The Gazette:
traffic_intervention:website=<url>
-----

I'd love to see other mappers using this scheme, as it is really
valuable to identifying both new and existing LTN changes.

Note that part of the intention of the tag is that it goes on the way
that has been changed. Thus it would be possible for an application to
parse the database, find traffic_intervention tags, change those ways
to "normal" highways open to motor vehicles, and run standard routing
software analysis to see where vehicles would be routed. That way it
is possible to evaluate how each intervention affects overall traffic
routing in an area.

Thus in the example in the OP (a diagonal modal filter) the short
cycleway joining the two sections of residential highway would be the
bit tagged with traffic_intervention=modal_filter (because that is the
bit necessary to change in order to revert the road network as
perceived by routers).

Stephen

On Sat, 10 Apr 2021 at 09:08, Steven Hirschorn
<steven.hirschorn at gmail.com> wrote:
>
> 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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