Amends subsection (d) (the provisions establishing and governing the Advisory Committee on Underride Protection) to modify committee membership (strike and redesignate certain clauses and add new clauses for families of underride crash victims who were occupants of passenger motor vehicles and families of victims who were Vulnerable Road Users), change meeting frequency and formats, change reporting frequency language from 'a biennial' to 'an annual', and add a termination date of September 30, 2031.

Adds new section 30130 to chapter 301 of title 49 establishing rulemaking, performance standard, compliance, cost‑benefit, and review requirements for side underride guards on trailers, semitrailers, and single unit trucks.

Amends the analysis for title 49 by striking the item relating to section 30128 and inserting a replacement item, and by inserting an item after the item relating to section 30129.

Redesignates existing paragraphs (11)-(13) as (12), (17), and (19); inserts new definitions into 30102(a) including definitions for 'passenger motor vehicle' (referencing 32101), 'Secretary' (means the Secretary of Transportation), 'semitrailer' (referencing 49 C.F.R. §571.3(b)), 'side underride guard' (definition specifying crash mitigation and prevention of Vulnerable Road Users sliding under trailers), 'single unit truck' (defined as a large commercial truck excluding any attached trailer), 'trailer' (referencing 49 C.F.R. §571.3(b)), and 'Vulnerable Road User' (referencing 23 U.S.C. 148(a)); and makes technical punctuation amendments to paragraphs (1)–(19).