Access tags in OSM like foot=no are intended to reflect actual legal restrictions rather than subjective opinions. In the UK, pedestrians have an absolute right to use highways unless explicitly prohibited (which requires legislation and a "pedestrians prohibited" sign).

Pedestrian routing software may use other OSM tags based on real properties of the road to assign a higher cost, including the 60mph speed limit which is already tagged. Other things which may be useful to add are the presence of sidewalks, verges, road width, lane count, whether it's lit, etc.

https://wiki.openstreetmap.org/wiki/Key:access