AASHTO HBP-1, Historic Bridge Preservation Guide, First Edition (2020), addresses the preservation and rehabilitation of fixed and movable historic highway bridges. The guide works through the general design and location features and the structural analysis and evaluation provisions that apply when an existing historic structure is retained rather than replaced. Vertical clearance improvement is treated as one of the recurring preservation measures, and buried structures and tunnel liners are also addressed. Preservation work is specified through provisions for cathodic protection systems, locating and removing near-surface metal, eliminating electrical discontinuities in reinforcing steel, and preparing surfaces and applying zinc anodes. These treatments support the continued service of a historic structure whose cultural value argues against replacement. The guide is intended for engineers and agency staff who must balance that cultural value against current functional and safety requirements.