6.10 Countermeasures to Improve Pavement Delineation

Good pavement surface markings allow drivers to (a) detect and recognize curves earlier, (b) reduce speeds appropriately, and (c) adjust their lateral position. Table 6.3 provides design guidance for markings. Table 6.4 lists the strengths of different markings.

Table 6.3 Countermeasures to Improve Curve Detection and Motorist Performance
Feature	Guidance
General	Pavement markings should have small gaps, long dashes, and short repetition cycles. Combining treatments increases their effectiveness.
Edge Line and Centerline	Use edge lines on (a) sharp or frequent curves, (b) narrow roads, or (c) near crossing roads and major driveways. Use the widest possible edge lines and centerlines to maximize their visibility. If possible, use durable striping materials with high retroreflectivity.
Raised Retroreflective Pavement Markers (RRPMs)	Combine RRPMs with edge lines and centerlines. On sharp curves (≥ 12 degrees), use pairs of RRPMs on the centerline’s outside edges. On flatter curves, a single RRPM is sufficient. Place RRPMs 787 ft upstream of a curve. On sharp curves, space RRPMs at 131 ft intervals. On flat curves, space RRPMs at 262 ft intervals.
Transverse Stripes	Implement transverse stripes as graduated rumble strips where possible. Install stripes so that drivers experience them at 0.5-second intervals when they decelerate at the desired rate (e.g. 2.95 m/s2).
SLOW Text with Arrow	In hazard-prone areas or locations with sharp curves, install a sign that reads SLOW and contains a directional arrow 230 ft upstream of the curve.

Table 6.4 Effects of Different Marking Types
Treatment	Benefits
General — Surface Markings	Strongest indication of downstream curvature Provide short-range steering control cues (compensatory control)
General — Post-Mounted Chevrons	Strongest guidance cues Provide long-range guidance (anticipatory control)
Combined Treatments	More effective than single treatments
Edge Line / Centerline	Best for curve recognition, curve perception, and reduction of lateral variability Discontinuities in edge lines help motorists detect downstream features such as driveways and intersections
RRPMs	Improved visibility of edge lines and centerlines Reduce lane encroachments Visual and rumble effects let motorists know they are encroaching on the shoulder or adjacent lane
Transverse Stripes	Reduced speeds May be most effective when combined with rumble strips
SLOW Text with Arrow	Reduced speeds Warns motorists of downstream curves

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