13'-6" is the Max Legal Height in the US the design height for new bridges not on the Interstate system is 14'-6", any bridge less than that is supposed to be posted in advance at a point where the driver can avoid or turn around the same goes for weight limits. Signs are stolen and vandalized.
The design height for new bridges on the Interstatesame is 16'-6", this does not apply to the non-interstate route at an interchange.
The American Association of State Highway Officials and the Federal Highway Administration set the standards.
Advice from an old bridge engineer