Signs and Markings: Coding, Placement, and Marking Geometry
Signs and Markings covers MUTCD Parts 2 and 3 the way a field or shop technician applies them: color and shape coding, mounting height and lateral offset, retroreflectivity management, and the geometry of longitudinal pavement markings.
Color and shape coding
- White legend on red = regulatory (STOP, YIELD, DO NOT ENTER).
- Black on yellow = warning; fluorescent yellow-green for pedestrian and school warnings.
- White on green = guide; white on blue = services; white on brown = recreational and cultural.
- Black on orange = temporary traffic control.
- STOP is the only octagon; YIELD the only inverted triangle; the railroad advance warning sign is a circle.
Placement
Bottom of a post-mounted sign at least 7 ft above the top of curb in business, commercial, or residential areas and at least 5 ft above the near roadway edge in rural areas. Lateral offset is about 12 ft from the edge of the traveled way in rural areas and roughly 2 ft from the curb face in urban areas. Signs inside the clear zone need breakaway or yielding supports.
Markings
Yellow separates traffic moving in opposite directions or marks the left edge of divided highways; white separates same-direction lanes and marks right edges. Longitudinal lines are normally 4–6 in wide. The lane-line pattern is a 10 ft line with a 30 ft gap; the 3 ft line/9 ft gap pattern is permitted only where speeds are 40 mph or less.
Worked example
A 2-mile segment of 55 mph three-lane highway. At 55 mph the 10/30 pattern applies. One cycle is 40 ft; 2 miles = 10,560 ft; 10,560 ÷ 40 = 264 cycles, so 264 ten-foot dashes = 2,640 ft of lane-line paint. Substituting the 3/9 pattern here would produce 880 dashes and a slow-speed marking pattern on a high-speed road.
Traps that cost marks
- Reversing yellow and white applications.
- Using the 3/9 pattern at 45 mph.
- Measuring mounting height to the top of the sign instead of the bottom.
- Treating retroreflectivity as permanent; the FHWA rule requires a documented management method (nighttime inspection, measured retroreflectivity, expected service life, blanket replacement, or management software).