Rights of way and other tracks may have sections enclosed by hedges, banks or walls, which have become sunken and eroded with time and use. The surfaces may be very rocky and rough, or muddy and liable to flood. Instead of resurfacing the entire width of the track, a raised surface or causeway can be constructed along one side, provided that this does not affect any vehicular rights along the route. Normally a sub-base of hard-core, large stones or other material will be needed to give sufficient height, topped with surfacing of aggregate, stone pitching, woodchips or concrete, according to the situation. A boulder and aggregate causeway was constructed up the side of an enclosed, eroded track at the southern end of the Pennine Way. During wet weather water flows down the old track, leaving the causeway dry and accessible.
Sustrans frequently build causeways using geotextiles and aggregates to raise cycle tracks through disused flooded railway cuttings. The ecological value of the flooded area is enhanced by confining access to the dry causeway at the side of the cutting.
