5.3 Longitudinal Channelizing Devices (LCDs), Temporary Pavement Markings, & Raised Pavement Markers

5.3 Longitudinal Channelizing Devices (LCDs), Temporary Pavement Markings, & Raised Pavement Markers

While point channelizers like cones and drums guide drivers through basic lane shifts, complex urban corridors, bridge rehabilitations, and pedestrian detours demand continuous longitudinal channelization and high-clarity pavement markings. Longitudinal Channelizing Devices (LCDs), temporary pavement marking lines, and Temporary Raised Pavement Markers (TRPMs) create clear visual pathways and eliminate driver confusion. IMSA Work Zone Technicians must ensure these systems meet MUTCD standards, Americans with Disabilities Act (ADA) accessibility guidelines, and strict marking obliteration rules.

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Longitudinal Channelizing Devices (LCDs)

Longitudinal Channelizing Devices (LCDs) are lightweight, interlocking plastic units designed to provide continuous visual channelization along work zone boundaries, tapers, and pedestrian walkways.

Visual Delineation vs. Structural Crash Barriers

Technicians must understand the critical operational difference between LCDs and positive structural protection barriers (such as Portable Concrete Barriers / Jersey Barriers):

• Longitudinal Channelizing Devices (LCDs): Constructed of hollow, high-density polyethylene plastic. They interlock end-to-end to form a continuous visual wall. While they prevent drivers from mistakenly steering between channelizing devices, standard LCDs are non-rigid channelizers and are NOT designed to contain or redirect impacting vehicles. They cannot be used in place of structural crash barriers where positive vehicle containment is required to protect workers or drop-offs.
• Portable Concrete Barriers (PCBs): Heavy concrete or steel structures designed and crash-tested to physically contain, absorb impact energy, and redirect errant vehicles away from hazardous work spaces.

+-----------------------------------------------------------------------+
|                    LCD vs. PORTABLE CONCRETE BARRIER                   |
+-----------------------------------------------------------------------+
| Feature           | Longitudinal Channelizer (LCD)| Concrete Barrier   |
| ----------------- | ----------------------------- | ------------------ |
| Material          | Hollow Plastic (Water-filled) | Reinforced Concrete|
| Primary Function  | Continuous Visual Guidance    | Vehicle Containment|
| Interlocking      | Light Pin / Latch Connection  | Heavy Steel Pin    |
| ADA Pedestrian    | YES (Smooth Top & Bottom Rail)| Requires Add-ons   |
| Vehicle Redirection| NO (Yields on Impact)        | YES (Structural)   |
+-----------------------------------------------------------------------+

ADA Accessibility & Pedestrian Guidance

When work zones disrupt sidewalk networks, LCDs are the preferred device for constructing temporary pedestrian access routes (TPARs). To comply with ADA standards and MUTCD Section 6K.02, pedestrian LCDs must include:

1. Detectable Bottom Edge: A continuous detection plate whose bottom is no higher than 2 inches above the walkway and whose top edge is at least 8 inches above the walkway, sharing a common vertical plane with the hand-trailing edge; where devices are combined in a series, the gap between devices should not exceed 1 inch, along the entire length, allowing visually impaired pedestrians using long canes to detect the barrier boundary.
2. Smooth Top Guidance Rail: A smooth, continuous top rail mounted at a height between 32 and 38 inches above the walking surface, allowing pedestrians to use it as a continuous hand-guidance rail without snagging clothing or hands.
3. No Protrusions or Trip Hazards: Interlocking joints and base supports must be flush, with no sharp edges or ballast legs protruding into the 60-inch minimum pedestrian clear path.

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Temporary Pavement Markings: Standards & Color Coding

Pavement markings provide continuous lateral guidance within travel lanes. In work zones where traffic is shifted, temporary pavement markings must clearly delineate new travel paths during daytime, nighttime, and adverse weather conditions.

Standard Color Coding and Line Meanings

Temporary pavement markings follow the exact same color standards as permanent markings:

• Yellow Markings: Delineate the left edge of divided highways, one-way roadways, and centerlines separating opposing traffic flows on two-way, two-lane roads.
• White Markings: Delineate the right edge of the roadway and separate travel lanes moving in the same direction.
• Black Contrast Markings: On light-colored concrete pavements, white retroreflective lines may feature black contrast borders to improve daytime visibility against sun glare.

Marking Materials and Performance Characteristics

• Temporary Pavement Marking Tape: High-performance retroreflective tape available in removable and non-removable grades. Removable tape uses specialized synthetic adhesives designed to adhere firmly during construction but pull up cleanly in long sections without scarring the pavement when traffic patterns shift.
• Temporary Traffic Paint: Fast-drying waterborne or solvent-based paint applied with retroreflective glass beads. Suitable for short-term shifts, though removal requires mechanical obliteration.
• Thermoplastic and Epoxy: Heavy-duty durable polymers used in multi-season, long-duration work zones where high traffic volume rapidly degrades standard paint.

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Obliteration & Eradication of Conflicting Pavement Markings

One of the most dangerous hazards in work zones occurs when drivers encounter old, obsolete pavement markings that conflict with temporary traffic shifts. Under wet pavement or low-sun angle glare conditions, conflicting markings confuse drivers and lead to head-on collisions or barrier impacts.

Mandatory Removal Criteria

MUTCD Guidance is that pavement markings in the temporary traveled way that are no longer applicable should be removed or obliterated as soon as practical, using a method that minimizes pavement scarring. The Standard is that painting over existing markings with black paint, or spraying with asphalt, shall not be accepted as a substitute for removal or obliteration.

Approved Removal Methods

1. Hydro-Blasting (Water Blasting): Ultra-high-pressure water jets (30,000+ psi) blast away marking material while vacuum recovery systems instantly collect water and debris. Hydro-blasting is the preferred method because it removes markings completely without deeply gouging the asphalt binder.
2. Sandblasting / Shot Blasting: Abrasive steel shot or aggregate blasts the surface, breaking down paint and tape. Effective on concrete surfaces.
3. Mechanical Grinding / Milling: Rotary grinding heads grind off markings. Technicians must control depth to avoid leaving deep longitudinal pavement grooves that trap vehicle tires.

       UNACCEPTABLE: BLACKOUT PAINT          ACCEPTABLE: HYDRO-BLASTING
    +----------------------------------+  +----------------------------------+
    |  Original Line Painted Over      |  |  Original Line Fully Eradicated  |
    |  ==============================  |  |  ..............................  |
    |  (Creates shiny "Ghost Line"     |  |  (Pavement texture restored;     |
    |   reflecting glare at night)     |  |   zero specular glare)           |
    +----------------------------------+  +----------------------------------+

Prohibiting Blackout Paint as a Permanent Solution

EXAM WARNING: Painting over conflicting markings with black paint ("blackout paint") is NOT an acceptable method of permanent pavement marking obliteration.

Over time, vehicle tire wear rapidly abrades blackout paint, exposing the bright underlying line. Furthermore, under rain or nighttime headlight glare, blackout paint reflects light differently than surrounding asphalt, creating a shiny, prominent "ghost line" that misleads motorists.

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Temporary Raised Pavement Markers (TRPMs) & Delineators

Temporary Raised Pavement Markers (TRPMs), commonly referred to as temporary marker tabs, are small, durable retroreflective plastic markers attached directly to the road surface.

Applications During Paving Operations

When highway resurfacing operations cover existing pavement markings with fresh asphalt overlay, permanent striping crews cannot apply painted lines immediately. TRPMs are installed on the fresh asphalt behind the paver to provide immediate, highly visible lane line guidance until temporary or permanent lines are painted.

• Protective Clear Covers: TRPM tabs installed ahead of asphalt distributors feature clear plastic protective covers. After liquid asphalt or chip-seal binder is applied, workers peel off the clear cover, revealing a clean, highly retroreflective marker surface.
• Spacing Standards: Where TRPMs substitute for broken line segments, a group of at least three retroreflective markers spaced no more than 5 feet apart shall be installed every 40 feet. Where they substitute for solid lines, markers shall be spaced no more than 10 feet apart, with retroreflective or internally illuminated units spaced no more than 20 feet apart.

Retroreflective Delineators

Delineators are small retroreflective units mounted on flexible posts or guardrail brackets along the outer edges of the roadway. Unlike channelizing devices, delineators are guidance devices only and are not considered channelizers. They indicate the alignment of the roadway, especially along sharp horizontal curves. MUTCD Section 3G.04 gives delineator spacing along curves based on radius, ensuring drivers see a continuous visual arc of retroreflective points leading through the curve.