SIGNING CULVERTS A culvert is defined as a tube of some construction over which a trail crosses, not including the backfill area at each end of the tube. A culvert should be marked with a Culvert Ahead or Slow sign on each approach to the culvert and Object Markers on each side of the culvert. (See Fig. 11) Any culvert that narrows the groomed trail surface needs to be marked. Culverts that do not narrow the trail do not necessarily need to be marked. FIGURE 11 CORRIDOR CORRIDOR CULVERT AHEAD SLOW 16 CORRIDOR CORRIDOR SLOW CULVERT AHEAD