[Code of Federal Regulations]
[Title 23, Volume 1]
[Revised as of January 1, 2007]
From the U.S. Government Printing Office via GPO Access
[CITE: 23CFR658.21]

[Page 288]
 
                           TITLE 23--HIGHWAYS
 
 CHAPTER I--FEDERAL HIGHWAY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION
 
PART 658_TRUCK SIZE AND WEIGHT, ROUTE DESIGNATIONS_LENGTH, WIDTH AND 
 
Sec.  658.21  Identification of National Network.

    (a) To identify the National Network, a State may sign the routes or 
provide maps of lists of highways describing the National Network.
    (b) Exceptional local conditions on the National Network shall be 
signed. All signs shall conform to the Manual on Uniform Traffic Control 
Devices. Exceptional conditions shall include but not be limited to:
    (1) Operational restrictions designed to maximize the efficiency of 
the total traffic flow, such as time of day prohibitions, or lane use 
controls.
    (2) Geometric and structural restrictions, such as vertical 
clearances, posted weight limits on bridges, or restrictions caused by 
construction operations.
    (3) Detours from urban Interstate routes to bypass of 
circumferential routes for commercial motor vehicles not destined for 
the urban area to be bypassed.