The language of “Section 13: Railing” in the AASHTO LRFD [Load and Resistance Factor Design] Bridge Design Specifications, published in 2007, has not had a major revision since LRFD specifications were adopted. Some of the text date back to the 1989 AASHTO Guide Specifications for Bridge Railings. Then, in 2009, MASH replaced the 1993 NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features for evaluating safety hardware devices. On January 7, 2016, AASHTO and FHWA signed a joint implementation agreement requiring all new permanent installation and full replacement of bridge rails on the national highway system in contracts let after December 31, 2019, to be compliant with MASH.

Therefore, there was an immediate need to update the bridge railing design requirements to incorporate MASH requirements and address outdated language and areas of ambiguity particularly related to loads, load distribution to bridge barriers and deck overhangs, railing geometry, and analysis methods for determining the demand and capacity of bridge barriers.

Under NCHRP Project 22-41, “Proposed Modification to AASHTO LRFD Bridge Design Specifications, Section 13—Railing,” Modjeski and Masters, Inc. was asked to (1) propose updates to bridge railing design requirements and (2) develop examples to demonstrate the application of the proposed updates. The research team suggested draft language for consideration by AASHTO in the next update of the LRFD Bridge Design Specifications and provided analysis and design examples to illustrate the proposed updates.

An appendix containing the analysis and design examples is available by searching for NCHRP Research Report 1109: Bridge Railing Design Requirements on the National Academies Press website (nap.nationalacademies.org).