Guiding Motorists through Turns and Curves

Large Single Arrow (W1-6)	Chevron (W1-8)

     Warning signs are principally for drivers unfamiliar with the road. The Manual of Uniform Traffic Control Devices (MUTCD) governs which signs to use, and how to place them. For turns and curves, it describes the W1 series. This article describes use and placement of two W1 series signs: the Large Single Arrow (W1-6) and the Chevron Alignment (W1-8) signs.

Where to Use W1-6 and W1-8 Signs

     W1-6 and W1-8 signs alert drivers, and guide them to the safe path through severe alignment changes. Road managers must install them based on engineering judgment. They should consider them for these situations:

• Where accident records show “run off the road”, “hit fixed object” or other turn or curve related crashes.
• Where accident evidence exists, such as shoulder damage, scars on trees, or other marks on shoulders.
• Where day or night inspection suggests drivers need warning of alignment changes.

     Large Single Arrow signs mark sharp turns and short curves. On conventional roads, the sign size is 48 by 24 inches. The MUTCD allows 36 x 18 inch W1-6 signs on low-speed roadways, where the reduced legend size would be adequate.
     Chevron Alignment signs mark curves and less than sharp turns. Chevron signs 18 by 24 inches are the standard for conventional roads. The MUTCD allows 12 x 18 inch W1-6 signs on low-speed roadways. They should not have the border shown in the above picture.

Sign Placement

     The MUTCD requires locating W1-6 and W1-8 signs on the outside of turns and curves at right angles to approaching traffic. The point of the Arrow or Chevron must indicate the direction of travel. They should be visible for at least 500 feet. The minimum lateral offset is 6 feet. Sign supports shall be breakaway or yielding. Crews may place the signs on existing supports, such as utility poles.
     Crews should install W1-8 signs in a series along the length of the turn or curve. They should space signs so drivers can always see two signs.
     Note: Compare the visibility of the supplemental panel for advisory speed with the advisory speed built into the sign. Also, note that drives can see two Chevrons.

Where Not to Use These Signs

    Cities and towns should not use these warning signs when the curvature and its severity are apparent to drivers. Excessive use tends to breed disrespect for signs. Municipalities should not use Chevron Alignment signs

1. On winding roads where drivers might see the last in a series of signs where the road begins to turn in the reverse direction, or
2. Where a turn or curve within the segment has inadequate length for proper sign spacing.

Further Information

     The MUTCD rules for Large Single Arrow and Chevron Alignment signs are in the Traffic Sign Handbook for New Hampshire Local Roads. It is available from the UNH T² Center.

Source:
Street Wise. Spring 2003, Nevada Transportation Center, Volume III, #1
Manual of Uniform Traffic Control Devices (MUTCD). Federal Highway Administration. http://mutcd.fhwa.dot.gov/

Special Thanks to Bill Lambert, NHDOT Traffic Engineer, for the photo.

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