Section 661.53 - What standards should be used for bridge design?(a)New and replacement. New and replacement structures must meet the current geometric, construction, and structural standards required for the types and volumes of projected traffic on the facility over its design life consistent with 25 CFR part 170, subpart D, appendix B.(b)Rehabilitation. Bridges to be rehabilitated, at a minimum, should conform to the standards referenced in 25 CFR part 170, subpart D, appendix B.