In the United Kingdom, a byway open to all traffic means a highway over which the public have a right of way for vehicular and all other kinds of traffic but which is used by the public mainly for the purpose for which footpaths and bridleways are used. (United Kingdom Road Traffic Regulation Act 1984, section 15(9)(c), as amended by Road Traffic (Temporary Restrictions) Act 1991, Schedule 1).

A byway open to all traffic is sometimes waymarked using a red arrow on a metal or plastic disc or by red paint dots on posts and trees.