|
 People
who live with vision impairment understand the true importance of detectable
warning systems as an aid that allows them to safely navigate pedestrian
street crossings, including curb ramps and blended transitions, certain
median and refuge islands, and rail lines. The requirement for universal
compliance is actually relatively recent. In July 2001, after a 10-year
suspension for research, the U.S. Department of Justice made installation
of detectable warning systems mandatory at such crossings.
Detectable Warning Surfaces
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here for more information online
ADOT Guidelines
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here for more information online
U.S. Department of Transportation
Federal Highway Administration
or “Looking into the Future”
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here for more information online
Accessible Public Rights-of-Way
Planning and Design for Alterations
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here for more information online
Revised Draft Guidlines for
Accessible Public Rights-of-Way
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 R304
Detectable Warning Surfaces
R304.1 General. Detectable warning systems
shall consist of a surface of truncated domes aligned in
a square or radial grid pattern and shall comply with R304.
R304.1.1 Dome Size. Truncated domes in a detectable warning surface shall have a base diameter of 23 mm (0.9 in) minimum to 36 mm (1.4 in) maximum, a top diameter of 50 percent of the base diameter minimum to 65 percent of the base diameter maximum, and a height of 5 mm (0.2 in).
R304.1.2 Dome Spacing. Truncated domes
in a detectable warning surface shall have a center-to-center
spacing of 41 mm (1.6 in) minimum and 61 mm (2.4 in) maximum,
and a base-to-base spacing of 17 mm (0.65 in) minimum, measured
between the most adjacent truncated domes.
R304.1.3 Contrast. Detectable warning surfaces shall contrast visually with adjacent gutter, street or highway, or walkway surfaces, either light-on-dark or dark-on-light.
R304.1.4 Size. Detectable warning surfaces shall extend 610 mm (24 in) minimum in the direction of travel and the full width of the curb ramp (exclusive of flares), the landing, or the blended transition.
R304.2 Location and Alignment
R304.2.1 Perpendicular Curb Ramps. Where
both ends of the bottom grade break complying with R303.3.4
are 1.5 m (5.0 ft) or less from the back of curb, the detectable
warning system shall be located on the ramp surface at the
bottom grade break. Where either end of the bottom grade
break is more than 1.5 m (5.0 ft) from the back of curb,
the detectable warning shall be located on the lower landing.
R304.2.2 Landings and Blended Transitions.
The detectable warning system shall be located on the landing
or blended transition at the back of curb.
R304.2.3 Alignment. The rows of truncated domes in a detectable warning surface shall be aligned to be perpendicular or radial to the grade break between the ramp, landing, or blended transition and the street.
R304.2.3 Rail Crossings. The detectable warning surface shall be located so that the edge nearest the rail crossing is 1.8 m (6 ft) minimum and 4.6 m (15 ft) maximum from the centerline of the nearest rail. The rows of truncated domes in a detectable warning surface shall be aligned to be parallel with the direction of wheelchair travel. |
