Communicating Changes in Horizontal Alignment (2006) / Chapter Skim
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Pages 29-33
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From page 29... ...
FIRST RECOMMENDATION Initial Proposed Statement The initial proposed statement is as follows: The first option in §2C.06 of the millennium edition of the MUTCD should be changed to read that horizontal alignment signs may be used in advance of situations where the roadway alignment changes, and should be used when the alignment change would result in an advisory speed equal to or lower than the posted speed limit. The Winding Road (WI-5)
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From page 30... ...
The wording that had been proposed here and reviewed by the practitioners referred explicitly to horizontal curves and not all instances where advisory speed plaques might be used. Final Proposed Statement The final proposed revision is for a new section that would be applicable only to horizontal curves and based, in part, on the 2003 wording is as follows: An Advisory Speed (W13-1)
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From page 31... ...
It is also recommended that further definition of the factors to be included in engineering studies related to horizontal curves be included in appropriate sections of the Traffic Control Device Handbook. It has been argued here that the existing definition of an "engineering study" is too general for the purposes of placing TCDs on horizontal curves; it is thus recommended that the inclusion of a more explicit list of factors to be considered be included in the definition.
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From page 32... ...
Final Proposed Statement The recommendation for development of such an expert system is still advanced although the proposed statement is modified: NCHRP should consider funding a project to develop an expert system that would incorporate the factors listed in the third recommendation and that would be used for guidance for traffic control device deployments (including advisory speeds) for horizontal curves.
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From page 33... ...
Finally, there was a comment regarding whether the existing arsenal of TCDs available for horizontal curves is "working." The United States has a crash rate that is among the lowest in the world, and the crash rate has decreased substantially over time. This decrease is due to good traffic engineering practice, among other things, and points to how well the system does work, not that it couldn't improve.
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