Traffic cones, drums and delineators all typically perform the same function; to channelize traffic. While delineators offer less "visible area" than cones or drum delineators, they are often used when site conditions require that they be left in place during non work hours. Because of their reduced "visible area", delineators are spaced at 1/2 of the MUTCD standard for traffic cones.
Traffic supply, Inc. stocks JBC's 42in tall "N" top (knob-top) delineators. Paired with a 12lb base, they're stable and offer an easy way to support CAUTION or survey tapes.
JBC Knob Top Delineator PI Sheet
Typical Maximum Spacing*:
In tapers:
Equal to 1/2 of the speed limit in feet; 12ft for a 25 MPH speed zone.
In tangents:
Equal to the speed limit in feet; 25ft for a 25 MPH speed zone.
Spacing should be reduced in curves, and near intersections and driveways.
*up to a maximum spacing of 25ft in tapers and 50ft for tangent sections.
JBC Dome top delineator PI sheet