Thanks for the context, and I can see the issue that most routing engines will still route along the road in addition to or instead of the dedicated mapped footpath network. I can understand why though, since not everywhere has the footpaths mapped out and many places there are no footpaths so it must route you along the road.

From a data point of view I just don't thing crossing=no is needed, does it mean you aren't allowed to cross or just that there's no dedicated infrastructure to cross.

If the crossing=no is to mean you aren't allowed to cross then that's incorrect, from a road rules point of view you're only forbidden to cross within 20m of a crossing, which around here is really only between the bus stop at https://www.openstreetmap.org/node/356553525 and the intersection of Milton/Grimes. Further along to the south/west you are allowed to cross.

If the crossing=to is to mean there is no dedicated infrastructure to cross, that's already implied by the lack of a highway=crossing node around here.

I don't think the common routing engines take crossing=no along a way into account for example https://www.openstreetmap.org/directions?engine=fossgis_valhalla_foot&route=-27.474418%2C152.994533%3B-27.476593%2C152.996762#map=18/-27.475192/152.995643&layers=N still seems to cross the road there (while these don't update straight away, I think they have updated their data by now).

I'm not sure what routing engine and profile you're using on your Journey Planner or how often you ingest data updates but it still crossing here https://jp.translink.com.au/plan-your-journey/journey-planner?searchDate=2025-07-01&searchTime=3%3A00pm&startLocationId=PL%3AEilNdW5ybyBTdHJlZXQsIEF1Y2hlbmZsb3dlciBRTEQsIEF1c3RyYWxpYSIuKiwKFAoSCXsKrLO4UJFrEXh1YkOolqpEEhQKEglHzWClr1CRaxEAf97zWqMCBQ&start=Munro+Street%2C+Auchenflower+QLD&endLocationId=ST%3Aplace_aucsta&end=Auchenflower+station&timeSearchMode=LeaveAfter&maximumWalkingDistance=4000&walkingSpeed=Normal&fareTypes=Free&fareTypes=Prepaid&fareTypes=Standard&serviceTypes=Express&serviceTypes=NightLink&serviceTypes=Regular&serviceTypes=School&transportModes=Bus&transportModes=Ferry&transportModes=Train&transportModes=Tram

Likely the solution likes with the routing engine in the profile rules, to weight more strongly against crossing where there is no highway=crossing so it'll still do so if you're in an area with no footpaths mapped, but it'll prefer taking you on a bit of a detour to cross at a designated crossing.