Updating Vertical Clearance Signing
Vertical clearances must be measured immediately after any construction or maintenance activity that could affect the minimum vertical clearance of a structure. If the minimum measured clearance is less than or equal to the existing signed clearance, then the clearance sign must be replaced or modified and the district oversize/overweight permit coordinator should be notified before traffic is allowed to pass under the obstruction. If the minimum measured clearance is greater than the existing signed clearance and the clearance buffer (described under "Signing Minimum Vertical Clearance") is less than two inches, then the clearance sign legend should be changed as soon as practicable. The following table summarizes these directions.
If the measured overhead clearance is... | Then... |
|---|---|
less than or equal to the existing signed clearance, | replace the signs and notify the district oversize/overweight permit coordinator prior to opening the roadway to traffic. |
greater than the existing signed clearance but not by at least two inches, | replace the signs. |
greater than the existing signed clearance by at least two inches, | existing signs are okay. |
NOTE: The actual measured clearance should be three inches greater than signed clearance. If the existing signed clearance is within an inch of the correct signed clearance (3 inches ±1 inch of the actual measurement), the warning signs do not require replacement. | |