Chapter 3A. General
Markings on highways have important functions in providing guidance and information for the road user. Major marking types include pavement and curb markings, object markers, delineators, colored pavements, barricades, channelizing devices and islands. In some cases, markings are used to supplement other traffic control devices such as signs, signals and other markings. In other instances, markings are used alone to effectively convey regulations, guidance, or warnings in ways not obtainable by the use of other devices.
Markings have limitations. Visibility of the markings can be limited by snow, debris, and water on or adjacent to the markings. Marking durability is affected by material characteristics, traffic volumes, weather, and location. However, under most highway conditions, markings provide important information while allowing minimal diversion of attention from the roadway.
Pavement markings can enhance roadway delineation with the addition of audible and tactile features such as bars, differential surface profiles, raised pavement markers, or other devices intended to alert the road user that a delineation on the roadway is being traversed.
The general functions of longitudinal lines are:
- A double line indicates maximum or special restrictions,
- A solid line discourages or prohibits crossing (depending on the specific application),
- A broken line indicates a permissive condition, and
- A dotted line provides guidance.
Each standard marking shall be used only to convey the meaning prescribed for that marking in this Manual. When used for applications not described herein, markings shall conform in all respects to the principles and standards set forth herein.
Before any new highway, paved detour, or temporary route is opened to traffic, all necessary markings should be in place.
Markings that are no longer applicable for roadway conditions or restrictions and that might cause confusion for the road user shall be removed or obliterated to be unidentifiable as a marking as soon as practical. Markings that must be visible at night shall be retroreflective unless ambient illumination assures that the markings are adequately visible. All markings on Interstate highways shall be retroreflective.
Markings may be temporarily masked with tape until they can be removed or obliterated.
Pavement and curb markings are commonly placed by using paints or thermoplastics; however, other suitable marking materials, including raised pavement markers and colored pavements, are also used. Delineators, object markers, barricades, and channelizing devices are visibly placed in a vertical position similar to signs above the roadway.
The materials used for markings should provide the specified color throughout their useful life.
Consideration should be given to selecting pavement marking materials that will minimize tripping or loss of traction for pedestrians and bicyclists.
Object markers and delineators should not present a vertical or horizontal clearance obstacle for pedestrians.
Markings shall be yellow, white, red, or blue. The colors for markings shall conform to the standard highway colors. Black in conjunction with one of the above colors shall be a usable color.
When used, white markings for longitudinal lines shall delineate:
- The separation of traffic flows in the same direction.
- The right edge of the roadway.
When used, yellow markings for longitudinal lines shall delineate:
- The separation of traffic traveling in opposite directions.
- The left edge of the roadways of divided and one-way highways and ramps.
- The separation of two-way left turn lanes and reversible lanes from other lanes.
When used, red raised pavement markers shall delineate roadways that shall not be entered or used:
When used, blue markings shall supplement white markings for parking spaces for persons with disabilities. When used, blue raised pavement markers shall indicate locations of fire hydrants along a roadway.
Black may be used in combination with the above colors where a light-colored pavement does not provide sufficient contrast with the markings.
When used in combination with other colors, black is not considered a marking color, but only a contrast-enhancing system for the markings.
The widths and patterns of longitudinal lines shall be as follows:
- A normal line is 100 to 150 mm (4 to 6 in) wide.
- A wide line is at least twice the width of a normal line. The width of the line indicates the degree of emphasis.
- A double line consists of two parallel lines separated by a discernible space.
- A broken line consists of normal line segments separated by gaps.
- A dotted line shall consist of noticeably shorter line segments separated by shorter gaps than used for a broken line. The width of a dotted line shall be at least the same as the width of the line it extends.
Broken lines should consist of 3 m (10 ft) line segments and 9 m (30 ft) gaps, or dimensions in a similar ratio of line segments to gaps as appropriate for traffic speeds and need for delineation.
A dotted line for line extensions may consist of 0.6 m (2 ft) line segments and 0.6 m (2 ft) to 1.8 m (6 ft) gaps. A dotted line for lane drop/add markings may consist of 0.9 m (3 ft) line segments and 2.7 m (9 ft) gaps.