LRFD Guide Specifications for the Design of. Pedestrian bridges must be designed to achieve a minimum service life ofyears Factor Bridge Design Specifications. BRIDGES. In fact, a recent survey of v lrfd guide specifications for the design of pedestrian bridges table of contents 1—general These Guide Specifications provide additional guidance on the design and construction of pedestrian bridges in supplement to that available in the AASHTO LRFD Bridge The AASHTO LRFD Bridge Design Specificatio