Re: http://www.openstreetmap.org/directions?engine=graphhopper_foot&route=52.62530%2C1.22115%3B52.62559%2C1.21839#map=17/52.62689/1.22147&layers=N

As per http://wiki.openstreetmap.org/wiki/Tag:highway=bridleway the pedestrian routing should permit access to highway=bridleway with designation=public_bridleway.

Alternatively generally presume foot=yes like the wiki Implies section, except where the way exists inside the country of Germany, in which case presume foot=no.