Footpaths are an important and separate network infrastructure as they are dedicated rights of way for pedestrians and other vulnerable users of the public realm.  Footpaths and pedestrian areas are the only part of the public realm provided for the safety and enjoyment of vulnerable users of the public realm.   Cyclists are not regarded as sufficiently vulnerable users for footpath access or use.  It is not legal to cycle on footpaths as it endangers pedestrians and other dedicated vulnerable users such as the disabled, babies in buggies, the young, elderly, visually impaired, the deaf or hard of hearing.  That this is regularly not enforced is immaterial (it is of note that a Dublin Bus filmed driving on a footpath in Rathfarnham a few months ago was an item on the main RTE News).  A separate network exists and is currently being developed or retrofitted for cyclists; on-road, off-road or as shared pedestrian & cycle paths.  It is somewhat arrogant to assume that deficiencies in the cycle network can be addressed by taking over the dedicated pedestrian network.  The footpath network for pedestrians only is constantly being developed to ensure safe access to vulnerable users of the environment. It has long been identified that a significant contributor to traffic congestion in urban areas it the perception that it is not safe for young children to walk anywhere, and in particular to school.  It is also considered unsafe for young people to cycle similar journeys. Millions of euros and previously punts have been spent on a wide range of initiatives to promote alternatives to driving children to school and sport with little effect.  Shared space initiatives in residential areas where no separate footpath was provided proved unpopular and is no longer proposed.  Multi-annual budgets are allocated to retrofit pedestrian infrastructure enhancement to make pedestrian only footpaths easier and safer to use.  Long straight through roads are converted to vehicular cul-decs where possible while maintaining pedestrian through traffic.  Pedestrian only short cuts to public transport infrastructure are being opened up where possible. Various design guides are provided to developers to incorporate pedestrian routes separate from vehicular routes. OSM tagging permits tagging infrastructure provided in the public realm as dedicated for pedestrians only as the dedicated access for pedestrians, as it is pedestrians only who have the right of way there and all other traffic crossing a footpath must give way.  To emphasise the nature and importance of footpaths, they are usually constructed of a material different to a road, concrete, and separated from a road by a raised kerb.  It’s similar to urban OSI maps at the 1:1000 scale where the kerbline for a footpath is shown as a continuous dotted line.  Pedestrians in turn cannot walk on a motorway where footpaths are not provided.  In some instances the separation of pedestrians on footpaths has to be reinforced by the erection of barriers and railings on kerb edges near schools, recreation facilities and heavily trafficked roads. Mapping footpaths is important both in indicating a separate pedestrian network required for their safety and the underground network of wayleaves, underground infrastructure as well as the public realm for vulnerable users of the public realm who need to be protected from motor traffic hazards.   The mapping of footpaths also highlights deficiencies.  Most pedestrian road traffic fatalities occur where footpaths do not exist.  For footpaths, access to all=No I feel is correct as footpaths are provided only for pedestrians.  How is it confusing that access to all is no because the access is Dedicated to pedestrians only?  I’m stressing ‘Dedicated’ here and tag accordingly.  Where no pedestrians are expected or allowed no footpaths are provided.  There is a clear difference between a rural road where there is usually no footpath and access is available to all, and an urban street where a separate footpath is required, provided, and dedicated for pedestrians only.  It would be hard to imagine a safe urban environment without footpaths.
In addition to the above, since the 1970s footpaths and soft verges where provided have played an increasing role in urban and suburban development.  Developers are required to install underground services for water, sewage, electricity and ICT (including broadband) in accordance with specified vertical and lateral separation under soft verges where provided and under footpaths where soft verges are not provided.  This is so that they can be easily located and accessed for repair or upgrade - hence the numerous covers and access points on footpaths.  Only surface water drainage and service cross-overs are supposed to be located under roadways.   Routing traffic off footpaths is important to protect underground service wayleaves as they are not designed for the weight of vehicular traffic.  
As for navigation, footpath and road navigation needs to be separate and as far as possibly different so that the vulnerable users of the environment can safely use that part of the environment dedicated to their use  Footpaths and kerbs are a distinct and important infrastructure with a clear purpose.  They also form their own network different from a road network.  Every mapper should realise that everyone is a pedestrian from when they get up until they lay down. Car users walk or run to and from their vehicles.  Cyclists walk or run to and from their bikes.  Infants and children are not allowed to control motor vehicles and are destined to be pedestrians. Pedestrians only walk or run and need their own safe network to enjoy and survive the experience
Kerbs are required and provided to separate a roadway from a footpath.  They define the footpath.  Sometimes kerbs have to be raised to ensure separation.  Even further sometimes railings and bollards are provided on the kerb to ensure separation of pedestrians from all other users, cyclists, motor vehicles and horses – frequently near schools, recreation areas, pedestrian areas, and along busy roads.
