Quote:
Originally Posted by Igoo65
Here in the United States bridges are required to have the height shortened by 12". This is so trailers of similar heights to the bridge can make it under them. It takes in account the height of the road changing due to paving. This is according to the MUTCD. Manual of Uniform Traffic Control Devices. Nobody sue me!
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I think this may be the rule you are referring to which does not apply to non Highway or Interstate roads
"The adopted criteria provide vertical clearance values for the various highway functional classifications (Table 19). These criteria are set to provide at least a 1-foot differential between the maximum legal vehicle height and the roadway, with additional allowances for future resurfacing. These clearances apply to the entire roadway width (traveled way and shoulders). A formal design exception is required whenever these criteria are not met for the applicable functional classification".
This is not to say there is not any other clarifications. These standards went into play in 1967 so older low clearances would simply avoid this rule by applying for "
A design exception is required if this standard is not met"
So unfortunately the rule is not hardened and is subjective and mostly applies to the Highways and Interstates for National Defense purposes.
This Bridge is primarily access for the small West Glacier village with very little commercial access needs other than the Forest and Parks Dept which those entities deal with low bridges all the time and I am sure all their vehicles are well under 13'6".