Bob Malme in a post to a regional transportation forum noticed that on a map of the now under construction Triangle Expressway thatthe NC 147 TOLL and NC 540 TOLL shields were purple. Any non-toll NC routes were the traditional black background. Bob references the 2009 NC Turnpike Annual Report which shows a map of the TriEx on page 17.
This would confirm a note I received informing me that at an unrelated meeting to the Turnpike, an NCDOT official said that local communities couldn't use purple for wayfinding projects because it is reserved for the upcoming toll roads.
The reason for purple? The FHWA Manual of Uniform Traffic Control Devices (MUTCD) requires it. From page 10 of the 2009 Edition of the MUTCD:
The Triangle Expressway will be completely tolled electronically. Most likely a 'TOLL' banner will be included above the 540 and 147 shields.J. Purple—lanes restricted to use only by vehicles with registered electronic toll collection (ETC)
So of course, the question is - What do you all think? Do you like the use of purple in a state highway shield? Have better suggestions? Your own prototype you'd rather suggest? Post and send away....
01 Use of the color purple on any sign shall comply with the provisions of Sections 1A.12 and 2A.10. Except as provided in Sections 2F.12 and 2F.16, purple as a background color shall be used only when the information associated with the appropriate ETC account is displayed on that portion of the sign. The background color of the remaining portion of such signs shall comply with the provisions of Sections 1A.12 and 2A.10 as appropriate for a regulatory, warning, or guide sign. Purple shall not be used as a background color to display a destination, action message, or other legend that is not a display of the requirement for all vehicles to have a registered ETC account.
Judging from the wording solely in this paragraph, it would seem to me that purple in the route markers would be a violation. But consider that the design of state route markers are simply left to states; there could be some ambiguity.
I'll plan to link it to my Future Interstates (and Toll Roads) site.
Since it's a state route marker, however, NC can probably get away with using purple anyway.