9.2 Pavement Marking Layout and Rules

9.2 Pavement Marking Layout and Rules

Pavement markings serve as a continuous guide, conveying regulatory constraints and warnings directly on the road surface. Markings are characterized by their colors, patterns, widths, and placements. Their design must comply with MUTCD Chapter 3 standards, which form a key subject area in the PE Civil Transportation exam.

Marking Colors and Meanings

The MUTCD defines specific colors for pavement markings, each representing a distinct traffic regulation or direction:

• Yellow Markings: Separates traffic flows in opposing directions. Yellow is also used for the left-edge line on one-way roadways, divided highways, and ramps.
• White Markings: Separates traffic flows in the same direction. White is also used for the right-edge line of the traveled way.
• Red Markings: Indicates roadways or lanes that shall not be entered or used by the viewer (e.g., "Wrong Way" or prohibited lanes).
• Blue Markings: Used to supplement white markings for parking spaces reserved for persons with disabilities.
• Purple Markings: Used to supplement lane line markings for toll lanes restricted to registered electronic toll collection (ETC) vehicles.

Line Patterns and Dimensions

The pattern of a line indicates the level of restriction it imposes:

1. Broken Line: Indicates that crossing the line is permitted. A standard broken line consists of a 10-foot line segment followed by a 30-foot gap, creating a repeatable 40-foot cycle.
2. Solid Line: Discourages or prohibits crossing. It is used for lane boundaries where lane changes are discouraged (e.g., approaching an intersection) or prohibited (e.g., double solid yellow lines for no-passing zones).
3. Dotted Line: Consists of short segments (typically 2 feet or 3 feet) and short gaps (typically 6 feet to 9 feet). Used to guide vehicles through intersections, lane transitions, or to mark lane drops.
4. Double Line: Indicates maximum restriction. For example, a double solid yellow line prohibits passing in both directions.

Line widths also convey hierarchy and meaning:

• Normal Width: Typically 4 to 6 inches wide.
• Wide Line: At least twice the width of a normal line (typically 8 to 12 inches). Used for channelizing lines, drop lanes, or exit gore areas.

Transverse Markings: Crosswalks, Stop Bars, and Yield Lines

Transverse markings are placed across the travel lanes and include stop lines, yield lines, and crosswalks.

1. Stop Lines (Stop Bars)

• Design: Solid white lines, 12 to 24 inches wide.
• Placement: Extended across all approach lanes. They must be placed at least 4 feet (preferably 8 to 15 feet) in advance of the nearest crosswalk or the intersection's edge.

2. Yield Lines ("Shark's Teeth")

• Design: Consist of a row of solid white isosceles triangles pointing toward approaching vehicles. Each triangle has a base of 12 to 24 inches and a height of 18 to 36 inches. The spacing between triangles is 3 to 12 inches.
• Placement: Used to indicate the point where vehicles must yield at roundabouts or unsignalized mid-block crossings.

3. Crosswalk Markings

• Standard Transverse: Consist of two solid white lines, 6 to 20 inches wide, spaced at least 6 feet apart.
• Continental (Longitudinal): Consist of solid white lines, 12 to 24 inches wide, spaced 12 to 60 inches apart, oriented parallel to traffic flow. They are highly visible and designed to avoid tire tracks.

Continental Crosswalk:
   |   |   |   |   |
===|===|===|===|===|===  <--- Stop Bar (12\"-24\" wide)
   |   |   |   |   |
  [ ] [ ] [ ] [ ] [ ]    <--- Continental Bars (12\"-24\" wide)
   |   |   |   |   |
===|===|===|===|===|===
   |   |   |   |   |

Two-Way Left Turn Lane (TWLTL) Markings

A Two-Way Left Turn Lane (TWLTL) is a transition lane in the center of a highway reserved for vehicles making left turns in either direction. The markings for a TWLTL are highly specific and frequently tested:

• Outer Bound: A solid yellow line on the outside of the lane, which discourages drivers from exiting the lane or passing.
• Inner Bound: A broken yellow line on the inside of the lane, which allows drivers to enter the lane to initiate their left-turn maneuver.
• Symbols: Opposing pairs of left-turn arrows are painted at regular intervals (typically spaced every 200 to 400 feet, and immediately after intersections).

Pavement Arrows and Word Messages

Word and symbol markings are used to guide, warn, or regulate traffic.

• Elongation Principle: Because drivers view pavement markings at a shallow angle, letters and symbols must be elongated in the direction of travel to appear proportional. The standard height for letters on high-speed roadways ($> 45\text{ mph}$) is 8 feet, while 6 feet is permitted on low-speed roadways ($< 35\text{ mph}$).
• Standard Words: The word "ONLY" is used in conjunction with turn lane arrows. "STOP" cannot be painted on the pavement unless accompanied by a stop line and a physical stop sign.
• Arrow Configurations: Turn arrows (through, left, right, or combination). When a lane is designated as a mandatory turn lane, the turn arrow symbol and the word "ONLY" are typically required.

Retroreflectivity and Raised Pavement Markers (RRPMs)

To remain visible at night, pavement markings must be retroreflective unless there is sufficient ambient light. This is achieved by embedding glass beads into the marking binder material during application.

• Marking Materials:
  • Waterborne Paint: Cost-effective but low durability (6 to 12 months).
  • Thermoplastic: Plastic binder that is heated and applied. Offers excellent durability (2 to 5 years), widely used on asphalt.
  • Epoxy / Polyurea: Liquid multi-component materials. Highly durable, works well on concrete.
  • Preformed Tape: Applied with adhesive. Often used for permanent markings on new asphalt or temporary work zones.
• Raised Pavement Markers (RPMs): Small plastic or metal blocks containing retroreflective lenses that are affixed to the pavement surface.
  • Color Coding: RPMs must match the color of the line they supplement. White RPMs supplement white lines, yellow RPMs supplement yellow lines, and red RPMs are mounted on the reverse side of markers (visible only to wrong-way drivers) to alert them.
  • Spacing: On tangent sections, RPMs are typically spaced at $N = 40\text{ ft}$ or $2N = 80\text{ ft}$ intervals to align with the cycle of broken lines. On curves, the spacing is halved ($N/2 = 20\text{ ft}$ or less) depending on the degree of curvature to provide better visual tracking.