George Hearn., "May 1991.", Technical Report number: CDOH/R/UCB-91-6., Issued by the Colorado Division of Transportation Development., Work performed and report written under Department of Highways; report published after agency name change to Department of Transportation., Print version record.
Final report., "Sponsored by the Colorado Department of Transportation In Cooperation with the U.S. Department of Transportation, Federal Highway Administration.", "February 2006.", "Report number CDOT-DTD-R-2006-7.", Includes bibliographical references (p. 108-111)., Mode of access: World Wide Web.
Positive protection is defined by Federal Highway Administration (FHWA) as "devices that contain and/or redirect vehicles and meet the crash worthiness evaluation criteria contained in NCHRP Report 350." By this definition, positive protection devices should prevent intrusion into the work area. These guidelines address the use of positive protection devices in work zones., "January 2010.", Online resource; title from PDF cover (viewed December 2015)
Cover title., "February 28, 2006.", "The guide was developed, prepared, and reviewed in 2006 by Clanton and Associates and a team of CDOT engineers representing all CDOT regions."--P. 1., Mode of access: World Wide Web.