WZSC Glossary

WZSC Glossary composed of MUTCD, NIOSH, OSHA, AASHTO

Browse the glossary using this index

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D

Dark Mode

The lack of all signal indications at a signalized location. (The dark mode is most commonly associated with power failures, ramp meters, hybrid beacons, beacons, and some movable bridge signals.) MUTCD 2009 Edition with May 2012 Revisions 1 and 2

dBA

A-weighted decibels

Decision Sight Distance

The distance required for a driver to detect an unexpected or otherwise difficult-to-perceive information source or hazard in a roadway environment that may be visually cluttered, recognize the hazard or its potential threat, select an appropriate speed and path, and initiate and complete the required safety maneuver safely and efficiently. See also Sight Distance, Stopping Sight Distance, Passing Sight Distance, and Intersection Sight Distance.

Keyword(s):

Delineator

A retroreflective device mounted on the roadway surface or at the side of the roadway in a series to indicate the alignment of the roadway, especially at night or in adverse weather. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

Design Speed

A selected speed used to determine the various geometric design features of a roadway. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

Design Vehicle

The longest vehicle permitted by statute of the road authority (State or other) on that roadway. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

Designated Bicycle Route

A system of bikeways designated by the jurisdiction having authority with appropriate directional and informational route signs, with or without specific bicycle route numbers.

Designated design speed

The speed established as part of the geometric design process for a specific segment of roadway.

Detectable

Having a continuous edge within 6 inches of the surface so that pedestrians who have visual disabilities can sense its presence and receive usable guidance information.

Detector

A device used for determining the presence or passage of vehicles or pedestrians. MUTCD 2009 Edition with May 2012 Revisions 1 and 2

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