[Talk-GB] Modal Filters and Low Traffic Neighbourhoods

[Michael Booth]

Interesting tool Martin, thanks for putting it together.

One thing I initially noticed with the LTNs data layer - it only seems 
to pick up roads with traffic_calming=* as traffic-calmed, rather than 
recognising roads which have individual traffic_calming=* nodes.

It would be good if your tool could flag roads with traffic calming 
nodes as well, otherwise it ends up missing a lot of traffic-calmed 
roads since there's 7x more nodes than ways tagged in the UK.


On 12/06/2021 20:53, Martin - CycleStreets wrote:
>
>
>> I think there are people who have come up with an algorithmic way of 
>> finding LTNs.
>
> We (CycleStreets) have been working on this over the last few months.
>
> I'm pleased to say we now have a beta map of locations available 
> specifically for the purpose of OSM mappers looking at it to find 
> cases where OSM data is missing or incorrect. (Coverage is currently 
> UK & Ireland.)
>
> https://ltns.cyclestreets.net/modalfilters/
> Password: i-am-an-osm-mapper
>
> This is not intended for general consumption at this stage - we are 
> keen to see OSM data fixes in place so that the analysis picks up 
> missing modal filters, and errors eliminated, before a more public map 
> release.
>
> Please have a good look round your area, to find cases where there 
> exists a modal filter on the ground, but we are not picking it up. 
> Please update the data in OSM :) Changes should be reflected in our 
> analysis a few days later. I've listed at the end of this message the 
> typical map data errors I've found while validating the data, which 
> mappers should particularly look out for.
>
> We know that the analysis is not yet 100% perfect, and some locations 
> we know are missed for particular reasons. I have noted the current 
> known shortcomings in the analysis at the end of this message.
>
>
>
> MODAL FILTER TYPES
> ------------------
>
> The term 'modal filter' is not an exact term, and there are various 
> potential interventions that could be covered. We have focussed on 
> those ordinarily understood to create LTNs, i.e. locations that 
> genuinely create filtering for cycling and walking, but which are not 
> just general-purpose walking/cycling links between areas.
>
>
> 1) Bollards in the middle of a highway
> --------------------------------------
>
> This scenario creates a gap through which cycles may pass but not 
> motor vehicles. (NB We do not include these on service roads, which 
> tend not to be relevant.)
>
> Example - Walnut Tree Way, Cambridge:
> https://ltns.cyclestreets.net/modalfilters/#17.6/52.229022/0.114147
> https://www.cyclestreets.net/location/15394/
>
>
> 2) Gap in the middle of a highway
> ---------------------------------
>
> This scenario is similar but uses a gap. We have set a low threshold 
> to avoid this picking up cycleways/walkways between streets. We also 
> have a range of heuristics to avoid finding snickets between parallel 
> roads and similar scenarios.
>
> Example - Hulton Street, Salford:
> https://ltns.cyclestreets.net/modalfilters/#17.18/53.471459/-2.274801
> https://www.cyclestreets.net/location/169671/
>
>
> 3) Gate in the middle of a highway
> ----------------------------------
>
> Similar to scenario 1 and 2, but a gate is used, with a gap at the 
> side. We have tried to eliminate cases where there is a gate providing 
> limited access to a private estate or commercial area, even if the 
> gate hasn't been marked as access=private, but this is hard to do 100% 
> reliably. Please ensure that gates are properly marked as private.
>
> Example - Adam and Eve Street, Cambridge:
> https://ltns.cyclestreets.net/modalfilters/#18.78/52.2053704/0.1335703
> https://www.cyclestreets.net/location/170090/
>
>
> 4) Continuation cycleable
> -------------------------
>
> This is where a sideroad doesn't quite meet the main road, but a 
> continuation allows people to cycle/walk through.
>
> Example - Melville Road, meets Holyhead Road, Coventry:
> https://ltns.cyclestreets.net/#16.24/52.410216/-1.521758
>
>
> 5) Continuation walkable
> ------------------------
>
> Similar to scenario 4, but these are only walkable. (In many cases I 
> suspect these are actually cycleable as there is no 'No cycling' sign, 
> but bicycle-yes is missing in OSM.) I believe there are probably a lot 
> of cases in OSM where the pedestrian link from the sideroad to the 
> main road are not present. Please do check thoroughly in your area!
>
> Example - Laverna Dale continuation, Dublin:
> https://ltns.cyclestreets.net/modalfilters/#16/53.373677/-6.382583
>
>
> 6) No entry except cycles: contraflow
> -------------------------------------
>
> This is where a 'No entry' sign has an 'Except cycles' plate added, 
> resulting in motor vehicles not being allowed to enter an area. These 
> are relatively new in the UK as the DfT only officially allowed such 
> signage about 10 years ago. We have avoided the marker showing the 
> contraflow being present at every point a sideroad joins to it - we've 
> tried to get just the entrance from main roads.
>
> Example - Malcolm Street, Cambridge:
> https://ltns.cyclestreets.net/modalfilters/#18.47/52.2083882/0.1221567
> https://www.cyclestreets.net/location/70472/
>
>
> 7) No entry except cycles, using a plug
> ---------------------------------------
>
> Similar to scenario 6, this is the older arrangement where a physical 
> gap exists, providing an entry for cycles into an area, allowing them 
> to bypass a No entry sign to the right. (We cover both the scenario of 
> the drawn-in cycleway joining to the same node as the junction itself, 
> as well as the scenario of it drawn connecting to the main road but as 
> a different node just to the left of the junction.)
>
> Example - Garlic Row, Cambridge:
> https://ltns.cyclestreets.net/modalfilters/#15.4/52.210281/0.151542
> https://www.cyclestreets.net/location/10303/
>
>
> 8) Bus gate
> -----------
>
> This is where bus lane cameras are used to create a very short section 
> of bus lane, through which only buses and cycles can legally pass 
> without being fined. (We have tried to avoid cases where a long 
> general bus lane alongside other traffic lanes contains a tiny section 
> of Way.)
>
> Example - Silver Street, Cambridge:
> https://ltns.cyclestreets.net/modalfilters/#17.82/52.200607/0.11464
> https://www.cyclestreets.net/location/150487/
>
>
>
> TYPICAL ERRORS IN OSM DATA
> --------------------------
>
> Typical issues in OSM data I have found while trying to validate the 
> analysis are as follows - please do have a look round your area and 
> check for OSM data fixes where you know there is a modal filter (as 
> defined as one of the above types).
>
> - Missing pedestrian/cycle links from the edge of a local street that 
> almost joins a main road (see the 'continuation' scenario cases above).
>
> - Gaps that physically include bollards but no bollards are present in 
> OSM at one/both end(s).
>
> - Gates not marked with access=private.
>
> - Bollards that have not been marked as bicycle=yes.
>
> - Missing contraflows.
>
> - Uses of highway=pedestrian where bicycle=yes is not explicitly 
> stated, despite it being obvious that cycling is not banned.
>
> - Things where the geometry actually matches a modal filter, but are 
> in areas which should be marked as access=private (and therefore not 
> really modal filters insofar as general road users are concerned).
>
> - It would be useful if continuation cases could have an est_width 
> added, so we can in future eliminate cases that look like 
> continuations but never actually had direct car links, i.e. genuinely 
> always were just narrow footways. We already have a rule of thumb on 
> this based on distance, but it would be useful to have this extra data.
>
> - General connectivity issues where a sideroad has a continuation to a 
> main road that has a cycleway along it, and the sideroad cycleway only 
> connects to the main road cycleway and not the road itself also.
>
>
>
> SHORTCOMINGS IN THE ANALYSIS
> ----------------------------
>
> The analysis is quite complex (basically pattern-matching using some 
> quite complex SQL statements) and we haven't yet zapped every bug.
>
> - We haven't managed to eliminate cases of gates leading to islands of 
> isolated roads (i.e. private housing estate or commercial estate) 
> where that island network actually includes a walkway providing a 
> second entry point. Please ensure such gates are marked as private so 
> these can be explicitly known to be private entrances.
>
> - Sometimes a bus lane that includes a very short section between the 
> two sides of a dual-carriageway ends up being shown as a bus gate.
>
> - In the cases where a continuation (local street almost touching main 
> road) has a walkway, if the main road has a pavement drawn in as a 
> separate Way, and the continuation walkway joins only to that pavement 
> and not the main road itself, we are not currently detecting it. This 
> is the problem that the pavement is not strongly associated in formal 
> connectivity terms with the main road itself.
>
> - We have a declumping mechanism that aims to de-duplicate cases, so 
> that for instance a short gap with bollards at either end doesn't end 
> up with potentially three matches (gap, bollard, bollard). This 
> currently has a slight side-effect whereby completely different modal 
> filters that happen to be very close physically have one of the two 
> zapped. We plan to add more intelligent rules to avoid zapping 
> combinations that logically are very unlikely to be the same thing. An 
> example is Bene't Street in Cambridge (cycle contraflow), at the 
> junction with King's Parade (gate barrier):
> https://www.cyclestreets.net/location/31307/
> https://www.cyclestreets.net/location/113048/
>
> - We aren't yet dealing with the scenario of gates at the edges of 
> parks, which need to be eliminated. There are genuine cases of modal 
> filters within parks which obviously need to be kept.
>
> - There are some edge-cases whereby a continuation actually has 
> multiple spurs coming off it from the same node, and none get picked 
> up, e.g. Riverside Cambridge where it joins Abbey Road:
> https://ltns.cyclestreets.net/modalfilters/#18.76/52.2108985/0.1374399
>
> - If a filter has been (pointlessly) chopped into two ways, we may not 
> detect this. Example at Poplar's Road, Walthamstow:
> https://ltns.cyclestreets.net/modalfilters/#17.49/51.576557/-0.010998
>
>
> Martin,                     **  CycleStreets - For Cyclists, By Cyclists
> Developer, CycleStreets     **  https://www.cyclestreets.net/
>
>
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