Every device in, upon, or by which any person or property can be transported on rails or tracks and to which all other traffic must yield the right-of-way by law at grade crossings, including trains, one or more locomotives coupled (with or without cars), other railroad equipment, and light rail transit operating in exclusive or semi-exclusive alignments. Light rail transit operating in a mixed-use alignment, to which other traffic is not required to yield the right-of-way by law, is a vehicle and is not considered to be rail traffic.

The horizontal and vertical space occupied by the rail system; includes track, ballast, rail systems, platforms and overhead catenary system. Horizontal area is typically measured from curb to curb or fence line to fence line. This area may be shared by a variety of vehicles or may be an exclusive rail corridor.

A device mounted on or in a road surface that has a height generally not exceeding approximately 1 inch above the road surface for a permanent marker, or not exceeding approximately 2 inches above the road surface for a temporary flexible marker, and that is intended to be used as a positioning guide and/or to supplement or substitute for pavement markings. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

A highway traffic signal installed to control the flow of traffic onto a freeway at an entrance ramp or at a freeway-to-freeway ramp connection. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

See Ramp Control Signal. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

An interval that follows a yellow change interval and precedes the next conflicting green interval. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

A sign that gives notice to road users of traffic laws or regulations.

Retroreflective material reflects light back towards the source. For example, retroreflective material reflects vehicle headlights so that signs, safety clothing, and other safety devices appear more visible to drivers at night.

A property of a surface that allows a large portion of the light coming from a point source to be returned directly back to a point near its origin.

The permitting of vehicles and/or pedestrians to proceed in a lawful manner in preference to other vehicles or pedestrians by the display of a sign or signal indications. MUTCD 2009 Edition with May 2012 Revisions 1 and 2