Hazardous Materials Transportation (PHMSA)

The federal hazardous materials transportation program — governed by the Hazardous Materials Transportation Act and codified at 49 U.S.C. §§ 5101–5128 — establishes uniform national rules for how 3 billion tons of hazardous materials move each year across the United States by truck, rail, air, and vessel. The Pipeline and Hazardous Materials Safety Administration (PHMSA), within the Department of Transportation, sets the rules: which materials are classified as hazardous (from explosives and flammable liquids to radioactive materials and infectious substances), how they must be packaged, labeled, marked, and placarded, who may handle and ship them, and what training is required. The Hazardous Materials Regulations (HMR) — published in 49 CFR Parts 100–185 — are among the most detailed and consequential safety regulations in the federal code, affecting virtually every industry that produces, ships, or receives chemicals, fuels, batteries, compressed gases, or biological materials. Violations carry significant civil penalties (in 2026, approximately $96,000+ per violation per day under the inflation-adjusted PHMSA CMP table) and criminal penalties up to $500,000 and 10 years imprisonment for knowing violations causing death or injury (49 U.S.C. § 5124). The 2023 East Palestine, Ohio train derailment — which involved cars carrying vinyl chloride and other hazardous materials — put the federal hazmat transportation framework under intense public scrutiny, driving new regulatory proposals around tank car safety, wayside detection technology, and train length and weight limits.

Current Law (2026)

Legal Authority

• 49 U.S.C. § 5101 — Purpose (protect against risks to life, property, and the environment during the commercial transportation of hazardous materials)
• 49 U.S.C. § 5103 — General regulatory authority (Secretary of Transportation prescribes regulations for the safe transportation of hazardous materials in commerce; classification, packaging, labeling, placarding, shipping papers, handling, storage, and emergency response)
• 49 U.S.C. § 5104 — Representation and tampering (unlawful to offer hazardous materials for transport unless properly classified, described, packaged, marked, labeled, and in proper condition; tampering with containers or labeling is a crime)
• 49 U.S.C. § 5107 — Hazmat employee training (anyone involved in hazmat transportation must be trained and tested; recertification every 3 years)
• 49 U.S.C. § 5108-5109 — Registration and fees (hazmat shippers and carriers must register with PHMSA and pay registration fees; fees fund emergency response planning and training grants)
• 49 U.S.C. § 5112 — Highway routing (PHMSA designates highway routes for radioactive materials; states and localities may impose hazmat routing restrictions consistent with federal standards)
• 49 U.S.C. § 5116 — Emergency response planning and training grants (Hazardous Materials Emergency Preparedness grants to states and Indian tribes for emergency response training and planning)

How It Works

Every day, more than one million shipments of hazardous materials move across the United States by highway, rail, water, air, and pipeline — gasoline, chemicals, explosives, radioactive materials, compressed gases, and more. PHMSA's Hazardous Materials Regulations (HMR, 49 C.F.R. Parts 171-180) govern how these materials are classified, packaged, labeled, transported, and responded to in emergencies.

PHMSA's regulations cover the entire lifecycle of a hazmat shipment under 49 U.S.C. § 5103. Shippers must classify materials into one of nine hazard classes — Class 1 (Explosives), Class 2 (Gases: flammable, non-flammable, toxic), Class 3 (Flammable liquids), Class 4 (Flammable solids), Class 5 (Oxidizers and organic peroxides), Class 6 (Toxic and infectious substances), Class 7 (Radioactive materials), Class 8 (Corrosives), and Class 9 (Miscellaneous, including lithium batteries and dry ice) — then package the material in UN-specification or DOT-specification containers tested and certified for that class, mark and label packages with hazard diamonds and UN identification numbers, prepare shipping papers describing the material, and placard vehicles carrying bulk quantities. Carriers must ensure vehicles meet safety standards and drivers hold a CDL with hazmat endorsement.

When a hazmat incident occurs — a spill, leak, fire, or release — first responders use the Emergency Response Guidebook (ERG), published by PHMSA in cooperation with Canadian and Mexican authorities, to identify the material from placards and UN numbers and determine protective actions. PHMSA's registration fees fund the Hazardous Materials Emergency Preparedness (HMEP) grant program, which provides approximately $28 million annually to states and tribes for response training and planning. Lithium batteries represent the fastest-growing compliance challenge: classified as Class 9 hazardous materials under 49 CFR § 173.185, batteries in phones, laptops, e-bikes, and EVs can overheat, catch fire (thermal runaway), and cause explosions. Special packaging requirements, quantity limits, and state-of-charge restrictions apply even to small consumer shipments, and several high-profile cargo aircraft fires have driven repeated regulatory updates for lithium battery transportation by all modes.

How It Affects You

State Variations

Implementing Regulations

• 49 CFR Part 171 — Hazardous Materials Regulations: General Information, Regulations, and Definitions: the foundational "Part 171" rules that establish the scope, applicability, and incident reporting requirements for the entire Hazardous Materials Regulations (HMR) system. Part 171 is the starting point — it defines who is subject to the HMR and what must happen when things go wrong:

  • § 171.1 — Applicability: the HMR apply to any person who offers hazardous materials for transportation in commerce and to any carrier transporting hazardous materials in commerce; the rule specifically extends to interstate, intrastate, and foreign commerce; PHMSA has broad authority to set regulations covering all modes — the Part 171 rules preempt inconsistent state and local hazmat regulations (with exceptions for certain enhanced state safety measures)
  • § 171.12 — North American cross-border shipments: facilitates cross-border hazmat transport between the U.S. and Canada and Mexico; a hazmat properly packaged and documented under Transport Canada's TDG (Transportation of Dangerous Goods) Regulations or Mexico's equivalent may be accepted in the U.S. without re-packaging; equivalence is not complete — certain U.S.-specific requirements may still apply; this provision is critical for cross-border trade in bulk chemicals, oil and gas products, and industrial materials
  • § 171.15 — Immediate incident notification (the 12-hour rule): any person in possession of a hazardous material when a reportable incident occurs must notify the National Response Center at 1-800-424-8802 (or 202-267-2675) as soon as practicable, but within 12 hours after the incident; reportable incidents triggering immediate notification include: a fire, violent rupture, explosion, or dangerous release of hazmat; evacuation of public areas; fatality or injury requiring hospitalization; specified levels of radioactive release; unintentional release from a rail car; and air incidents involving forbidden materials; the 12-hour clock runs from the time the person first becomes aware of the incident — not from when it was reported internally
  • § 171.16 — Detailed incident reports (DOT Form 5800.1): within 30 days of each incident reportable under § 171.15 (and for certain additional incident categories), the person in possession must file a detailed written report using DOT Form 5800.1 (the Hazardous Materials Incident Report); the form captures incident location, carrier, shipper, material involved, quantity released, cause, injuries, deaths, and property damage; these reports feed PHMSA's hazmat incident database (available at PHMSA's website) — the primary data source for evaluating HMR effectiveness and identifying emerging hazmat risk patterns; the East Palestine, Ohio derailment (2023) generated extensive Form 5800.1 reporting and triggered a review of the incident reporting framework

  The combination of § 171.15 immediate notification and § 171.16 detailed reporting creates the federal hazmat incident tracking system that enables PHMSA, DOT, EPA, and emergency responders to identify systemic problems and improve safety requirements. The National Response Center (NRC) is also the notification hub for oil spills under the Clean Water Act (33 CFR Part 153) and CERCLA releases (40 CFR § 302.6) — a single call to 1-800-424-8802 simultaneously notifies multiple federal agencies for incidents with cross-jurisdictional implications.

• 49 CFR Part 172 — Hazardous materials table, hazard communication, placarding, emergency response

• 49 CFR Part 173 — Shippers: General Requirements for Shipments and Packagings (234 sections — the classification and packaging rules that shippers must follow before tendering hazmat to a carrier):

  • Subpart A — General (§§ 173.1–173.24): authorized packaging types (DOT specification packaging, UN standard packaging, and limited exemptions); proper shipping names and UN numbers cross-reference the Hazardous Materials Table at § 172.101; packing groups I (greatest danger), II (medium danger), III (minor danger) determine packaging rigor; quantity limits and forbidding certain materials from certain modes (e.g., certain compressed gases forbidden in passenger aircraft)
  • Subpart B — General Requirements Applicable to All Hazardous Materials (§§ 173.24–173.36): packaging closures must be tight; compatibility between packaging material and contents (plastic containers incompatible with certain solvents; glass prohibited for certain substances); overpacks and combination packages (inner packaging in outer packaging — the standard commercial configuration); salvage drums for damaged packages; reconditioned packaging requirements; limited quantity exceptions (small quantities in consumer-type packaging — retail quantities of many common materials need only limited quantity labeling, not full hazmat placards)
  • Hazard class-specific subparts: each of the 9 hazard classes has dedicated sections — Class 1 (Explosives) § 173.50–173.99 (compatibility groups, division classifications — 1.1 through 1.6); Class 2 (Gases) § 173.115–173.169 (flammable, non-flammable, toxic gas); Class 3 (Flammable Liquids) § 173.120–173.159 (flash point thresholds, packing groups); Class 4 (Flammable Solids, Spontaneous Combustion, Water-Reactive) § 173.170–173.250; Class 5 (Oxidizers and Organic Peroxides) § 173.127–173.145; Class 6 (Toxic and Infectious Substances) § 173.133–173.197 (Category A/B infectious, clinical specimens); Class 7 (Radioactive) § 173.403–173.476; Class 8 (Corrosives) § 173.154–173.159; Class 9 (Miscellaneous) including lithium batteries (§ 173.185 — watt-hour rating thresholds, state of charge limits, packaging requirements for Section IA/IB/II); magnetized materials; dry ice

• 49 CFR Part 174 — Carriage by Rail (48 sections across 9 subparts — PHMSA's rail-specific hazmat handling rules that apply in addition to the shipper packaging and classification requirements in Parts 171–173; prescribes what railroads must do when they accept, handle, and transport hazardous materials in rail cars and intermodal containers):

  • § 174.14 — Movement must be expedited: railroads must forward each hazmat shipment promptly and within 48 hours of receipt (excluding weekends and holidays); shipments may not be held for non-safety reasons; the expedite requirement reduces the time hazmat sits in rail yards and reduces exposure to weather, theft, or accidental release
  • §§ 174.24–174.30 — Damaged, leaking, or astray shipments: if a hazmat shipment is found damaged or leaking in transit, the railroad must immediately report to the National Response Center (under 49 CFR § 171.15/171.16), protect the public from the hazard, prevent further spillage or release, and contact the shipper; the railroad may not continue transporting a leaking package; disposition of damaged packages (repair, transfer to alternative packaging, or return to shipper) must follow specific procedures
  • § 174.45 — Placarding and inspection: railroads must inspect cars, tanks, and containers for proper placards before accepting for transportation; if required placards are missing, the railroad must refuse the shipment or properly placard it before movement; the railroad cannot rely solely on the shipper's documentation — visible inspection for placard compliance is the carrier's independent obligation
  • § 174.55 — Switching: rail cars containing Division 1.1 or 1.2 (high explosives) materials may only be switched on tracks free from obstructions; switching speeds for cars containing hazmat must be controlled to prevent collisions; cars must not be humped (dropped over a hump yard classification hill) when containing certain hazard classes unless the specific car design permits it
  • Subpart C — General Handling and Loading Requirements (§§ 174.55–174.86): cars must be kept away from fire; smoking is prohibited near hazmat cars; brakes on hazmat cars must be applied when standing; fueling of locomotives near hazmat cars is restricted; refrigerator cars used to transport hazmat must maintain temperature; Class 7 (radioactive) materials have minimum separation distances from occupied areas in the rail yard
  • Subpart D — Placarded Cars Handling (§§ 174.81–174.86): placard requirements for cars, transport vehicles, and freight containers reflect the most hazardous material aboard; railroads must maintain records of hazmat car locations within their system ("consist" — the required list of all hazmat cars in a train); the consist must be accessible to emergency responders and must identify each hazmat car's contents, quantity, and emergency contact
  • Subpart E — Explosives (§§ 174.101–174.115): Division 1.1 and 1.2 explosive materials require specific car selection (closed, structurally sound), car certification, route restrictions (certain rail routes prohibited for explosive shipments in quantities above threshold), and recordkeeping of car seals; car magazines (small wooden inserts for low-quantity high explosives) are authorized under specific construction requirements; mixed loading prohibitions (§ 174.102) prevent certain incompatible explosive subclasses from sharing a car
  • Subpart F — Class 2 Gases (§§ 174.200–174.204): pressure tank cars (DOT-105, DOT-112, DOT-114) carrying compressed gases must be kept away from heat sources; tank cars carrying poisonous gas (chlorine, phosgene, hydrogen cyanide) must meet enhanced separation requirements in yards and during transit; cars carrying flammable compressed gases must not be left standing on tracks adjacent to occupied structures

  Part 174 represents the railroad's side of the hazmat transportation compliance equation — while Part 173 governs what shippers must do before tender, Part 174 governs what the railroad must do once it accepts the shipment. The East Palestine, Ohio derailment (February 3, 2023) involved a Norfolk Southern train whose cars contained vinyl chloride, butyl acrylate, and other regulated materials; post-incident investigations examined whether Part 174's car handling, inspection, and emergency response procedures were followed and whether the wayside defect detection system failures contributed to the derailment.

  Recent rulemakings: 87 FR 79783 (December 2022) — updated emergency response information requirements for certain hazmat shipments by rail; 66 FR 45383 (August 2001) — major consolidation of rail hazmat requirements integrating INTERMODAl container handling into Part 174.

• 49 CFR Part 175 — Carriage by Aircraft (27 sections — the air-carrier-specific hazmat rules that apply in addition to the shipper requirements in Parts 171–173; among the most restrictive of any transport mode because fire, pressure, and toxic release in an aircraft are near-impossible to mitigate in flight):

  • § 175.10 — Passenger and crewmember exceptions: passengers may carry limited quantities of certain hazmat in carry-on or checked baggage — up to 2 kg of dry ice, personal care aerosols not exceeding 0.5 kg each (up to 2 kg total), alcoholic beverages under 24% ABV without limit / 24–70% ABV limited to 5 liters per person, medical devices with lithium batteries in carry-on; crewmembers and operators may carry first aid kits, fire extinguishers, and safety equipment; these "consumer commodity" exceptions are the reason TSA security regulations separately track what passengers can and cannot carry
  • § 175.20 — Training requirement: air carriers may not transport any hazmat unless every "hazmat employee" involved in that transportation — acceptance agents, cargo handlers, passenger agents — has been trained to the requirements of 49 CFR Part 172 Subpart H; training must cover the carrier's specific procedures, recognition of undeclared hazmat, and emergency response
  • § 175.25 — Passenger notification: every for-hire air carrier must inform passengers about hazardous materials restrictions — what may not be brought aboard, consequences of undeclared hazmat, and how to report suspicious packages; notifications are required at check-in (ticket counter or web check-in), airport gate areas, and in-flight; the recurring announcements at security checkpoints warning about liquids, aerosols, and gels implement this requirement
  • § 175.30 — Pre-acceptance inspection: aircraft operators must inspect each hazmat shipment before accepting it — verify the material is authorized for air transport, confirm labeling and marking are correct, check for damage or leakage, and confirm that the shipper's declaration is complete; undeclared hazmat discovered during acceptance is the most common enforcement trigger
  • § 175.33 — Pilot notification: the operator must give the pilot-in-command written notice (NOTOC — Notice to Captain) of every regulated hazmat shipment aboard, including quantity, location in the aircraft, and emergency response information from the Emergency Response Guidebook (ERG); the NOTOC must be retained for 30 days after the flight
  • § 175.501 — Oxidizer/oxygen restrictions: compressed oxygen for medical use may be loaded in passenger compartments only when authorized; limits on oxidizer quantities in cargo holds relative to adjacent flammable materials; Class 5 (oxidizing) materials are limited in total quantity per aircraft and must be separated from flammable materials
  • § 175.700 — Radioactive material limits: Class 7 materials face transport index (TI) limits per package, per compartment (cargo or passenger), and per aircraft; minimum separation distances between packages containing fissile material and between packages and occupied areas; the transport index system controls cumulative radiation exposure to crew and passengers

  Air transport's strict quantity limits and passenger cabin restrictions stem from post-accident investigations (including concealed explosive shipments) and the unique emergency environment — unlike highway or rail incidents, an in-flight hazmat event cannot be abandoned on the side of the road. The International Air Transport Association (IATA) Dangerous Goods Regulations, to which U.S. carriers are required to comply, are generally more restrictive than 49 CFR Part 175 on many items.

• 49 CFR Part 176 — Carriage by Vessel (114 sections — the maritime-specific hazmat handling rules that apply in addition to the shipper requirements in Parts 171–173; governs how carriers transport hazardous materials aboard U.S.-flag and foreign-flag vessels in U.S. ports, harbors, and navigable waters; administered jointly by PHMSA and the U.S. Coast Guard):

  • § 176.3 — Unacceptable shipments: a carrier may not transport a hazardous material by vessel unless it has been prepared in conformance with Parts 171–173 and accompanied by proper shipping papers; carriers must refuse packages that do not meet HMR requirements — the carrier's acceptance obligation includes inspection for correct labeling, marking, and packaging condition
  • § 176.11 — IMDG Code exception: a hazardous material may be transported by vessel in conformance with the International Maritime Dangerous Goods (IMDG) Code (the international standard published by the IMO) as an alternative to Part 176's specific requirements; this alignment provision allows international shipments to move without repackaging when they meet IMDG standards — practical for container cargoes moving through U.S. ports that originated or will terminate abroad
  • § 176.15 — Enforcement: a USCG enforcement officer may board any vessel at any time within U.S. jurisdiction to inspect cargo, shipping papers, and stowage — no advance notice required; enforcement authority is concurrent with PHMSA, but for vessel operations, USCG is the operational enforcement presence
  • § 176.18 — National Cargo Bureau: the NCB (a non-governmental marine inspection organization) is authorized to assist the USCG in inspecting vessels for proper stowage of hazmat cargo, issuing certificates of fitness, and certifying container packing; NCB inspections reduce the USCG burden at busy ports
  • § 176.24 — Shipping papers: carriers may not accept or transport hazmat by vessel without receiving a shipping paper (or dangerous cargo manifest) prepared per Part 172; for vessel transport, the shipping paper must identify the proper shipping name, UN number, hazard class, and stowage category
  • § 176.27 — Certificate: carriers may not transport hazmat by vessel without a certificate prepared per § 172.204; for containerized shipments, the shipper must certify that the container has been packed in accordance with HMR requirements — the container packing certificate shifts responsibility for interior packing to the shipper/packer
  • § 176.30 — Dangerous cargo manifest: the carrier must prepare a dangerous cargo manifest (or list/stowage plan) that identifies all hazmat aboard by location in the vessel — hold number, deck, or container position; this manifest enables emergency responders to immediately locate hazmat aboard a vessel during a fire, collision, or grounding without searching the ship
  • § 176.36 — Preservation of records: shipping orders, manifests, cargo lists, stowage plans, and all related records must be retained for at least 1 year after the voyage; the carrier (not the shipper) holds the vessel-side records obligation
  • § 176.100 — Class 1 (explosive) vessel permit: before Divisions 1.1 and 1.2 (high explosive) materials may be loaded or unloaded at any U.S. port, the carrier must obtain a permit from the COTP (Captain of the Port — the local USCG commander); the permit process allows the COTP to assign a supervisory detail (§ 176.102) and impose local port conditions; Division 1.4 (consumer fireworks) and 1.3 materials are subject to less restrictive requirements
  • §§ 176.116–176.194 — Class 1 (explosive) stowage rules: explosives must be stowed in a cool part of the ship away from heat sources; electrical equipment in explosive compartments must be de-energized; lightning protection required; only electric lights (not arc lights) during loading/unloading; flag "B" (Bravo) must be flown while explosives are being handled; only Division 1.4 explosives may be transported on passenger vessels
  • §§ 176.200–176.230 — Class 2 (compressed gas) stowage: pressurized gas cylinders must be prevented from contact with metal decks and secured against movement; must be stowed in mechanically ventilated spaces with no artificial heat sources; no smoking near any Division 2.1 (flammable gas) stowage
  • §§ 176.305–176.340 — Class 3 (flammable liquid) stowage: flammable liquids must be kept as cool as practicable, away from heat sources; a fire extinguisher required for every 21,000 gallons of flammable liquid in portable tanks; no smoking near flammable liquid cargo holds; hand flashlights must be explosion-proof

  Part 176 is the vessel mode's analog to Part 174 (rail) and Part 177 (highway) — the same hazmat classification and packaging requirements from Parts 171–173 apply, but the stowage, segregation, handling, and port procedures are adapted to maritime operations. The IMDG Code exception (§ 176.11) is the most practically significant provision: because most international container traffic already conforms to IMDG, vessels can move through U.S. ports without repackaging for domestic requirements. The dangerous cargo manifest (§ 176.30) and the USCG enforcement presence (§ 176.15) create a real-time hazmat tracking system for vessels in U.S. waters — essential when a vessel incident can affect port operations, neighboring vessels, and waterfront facilities simultaneously.

• 49 CFR Part 177 — Carriage by Public Highway (20 sections — the motor carrier requirements that apply when transporting hazardous materials by road, supplementing the shipper rules in Parts 171–173 and the driver-specific rules in 49 CFR Part 397):

  • § 177.800 — Compliance and training: motor carriers and their hazmat employees who prepare or transport shipments must comply with all applicable HMR requirements; training is required per Part 172 Subpart H
  • § 177.817 — Shipping papers: the driver must carry the shipping paper (bill of lading or manifest) for all hazmat shipments; the paper must be within reach of the driver while driving; when the driver is not in the vehicle, the paper must be in the driver's door pocket or on the driver's seat, visible to anyone opening the cab door — designed for emergency responders to immediately identify what's aboard
  • § 177.834 — General loading and handling: packages must be secured against movement during transport; flammable hazmat may not be loaded into a closed vehicle with an internal combustion engine unless the engine is off; no smoking within 25 feet of a vehicle containing flammable materials; vehicles must be attended while flammable, explosive, or poisonous gas materials are being loaded or unloaded
  • § 177.835 — Explosives (Class 1): engine must be stopped before loading or unloading; Division 1.1/1.2/1.3 explosive materials require a vehicle placarded "EXPLOSIVES" to be attended at all times and may not be parked in a tunnel or within 300 feet of a bridge, building, or crowd
  • § 177.837 — Flammable liquids (Class 3): engine must be stopped before loading or unloading unless engine is needed to operate mechanical handling equipment; bonding (static electricity grounding) required for tank vehicles; cargo tanks must not be transported if loaded above their approved maximum gross weight
  • § 177.841 — Poisonous (Class 6) materials: edibles — food, feed, medicine — must be separated from poisonous materials in cargo compartment if the poisonous material is in a package of 30 kg/30 liters or less (small package rule); larger shipments of poison may not be transported in the same freight compartment as food
  • § 177.810 — Vehicular tunnels: state and local tunnel authorities may impose routing restrictions on hazmat vehicles; 49 CFR does not preempt these restrictions — the HMR explicitly defers to tunnel authority rules for certain materials; this means drivers must know which tunnels in their area are closed to specific hazmat and what alternative routes are required

  The practical highway compliance burden concentrates on four items: proper shipping papers in reach, vehicle placards (§§ 177.823, 172.504), immediate emergency reporting if a release occurs (§ 177.854 — notify the NRC within 24 hours), and route restrictions under 49 CFR Part 397 (routing of radioactive materials and certain other high-hazard shipments requires state-approved routes or advance notification). The FMCSA (not PHMSA) enforces the driver-qualification and hours-of-service rules that run alongside Part 177 for CMV drivers transporting hazmat.

• 49 CFR Part 178 — Specifications for Packagings (254 sections — the engineering and testing standards that packaging manufacturers must meet before packaging can be marked as authorized for hazmat use):

  • Subpart B — Non-bulk Packaging Standards (§§ 178.100–178.235): design specifications and test requirements for steel, aluminum, fiber, wood, and plastic drums; jerricans; boxes; bags; and composite packagings; each packaging type has a UN standard code (e.g., 1A1 = steel drum, open head; 4G = fiberboard box); manufacturers must test each packaging design through drop tests, stacking tests, and hydrostatic pressure tests; test certificates must accompany each production lot; packagings are marked with the UN code, performance level, test date, and manufacturer identifier
  • Subpart L — Bulk Packaging Standards (§§ 178.700–178.810): intermediate bulk containers (IBCs) — both rigid (metal, plastic) and flexible (woven polypropylene super sacks) IBCs; each has design, testing, and marking requirements; portable tanks for liquid and solid hazmat shipments; ton containers for compressed gases
  • Performance vs. specification packaging: the HMR transitioned from prescriptive DOT-specification containers (each with a specific design blueprint) to UN performance-based standards (containers that pass standardized tests); most modern packaging is UN-coded; certain legacy DOT specification cylinders and containers remain in use and authorized

• 49 CFR Part 179 — Specifications for Tank Cars (179 sections — the engineering standards that railroad tank cars must meet before they can carry hazardous materials in bulk; directly relevant after the East Palestine derailment scrutiny focused on DOT-111 and DOT-117 tank car standards):

  • Subpart B — General Design (11s): applicable to all tank car types; general structural requirements including tank material grades, weld inspection requirements, head thickness, stub sill integrity, and structural integrity testing; all tank cars must bear a specification stencil (e.g., "DOT-117R") on the tank shell identifying the applicable specification
  • Subpart C — Specifications for Pressure Tank Cars (31s): covers DOT-105, DOT-109, DOT-112, DOT-114, and DOT-120 tank cars — high-pressure vessels designed for materials such as LPG, anhydrous ammonia, chlorine, and other toxic-by-inhalation (TIH) hazardous gases; shells are thicker-walled (3/8–1/2 inch steel) with normalized steel; top and bottom shelf couplers, full-height head shields, and thermal protection are required for certain high-hazard materials; pressure relief devices must be set at the applicable tank test pressure; normalized tank heads provide crush resistance in derailment
  • Subpart D — Specifications for Non-Pressure Tank Cars (66s): covers the workhorse general-purpose liquid bulk tank cars — DOT-111 (the legacy standard, widely used for ethanol, crude oil, and liquid chemicals), DOT-115 (a newer enhanced tank design), and the post-2015 retrofit/new-construction DOT-117 and DOT-117R/117P standards mandated for flammable liquids following the Lac-Mégantic disaster; DOT-117 requires 9/16-inch steel shells, full-height end-of-car head protection, top fittings protection, thermally protected tank jackets, and high-flow pressure relief valves; the Phase-in deadlines (completed by 2029) require the entire high-hazard flammable train (HHFT) fleet to meet DOT-117 or equivalent standards; DOT-111 cars not retrofitted to DOT-117R specification may not carry Packing Group I flammable liquids in HHFTs
  • Subpart E — Specifications for Multi-Unit Tank Cars (19s): covers DOT-106A and DOT-110AW tank car units — small-capacity (5,000–10,000 gallon) non-insulated containers mounted on flat cars in groups of two to five; primarily used for chlorine and small-lot chemical shipments; these specifications require thicker walls (3/8 inch steel minimum) and specialized valve protection given their smaller cross-section
  • Subpart F — Specifications for Cryogenic Liquid Tank Cars (44s): covers DOT-113 and DOT-107A tank cars for cryogenic liquids at or below −90°C — liquid natural gas (LNG), liquid argon, liquid nitrogen, and liquid oxygen; double-walled vacuum-insulated tank design with an inner stainless steel vessel surrounded by an annular insulation space; relief valves must safely vent as product warms; the 2020 LNG-by-rail rule expanded use of DOT-113C120W cars for LNG transport (subject to ongoing litigation)

• 49 CFR Part 180 — Continuing Qualification and Maintenance of Packagings (39 sections — PHMSA's lifecycle requalification requirements for packagings placed in service; Part 178 governs initial design certification; Part 180 governs how certified packaging must be maintained, inspected, retested, and marked throughout its working life):

  • § 180.1 — Purpose: once authorized packaging enters service, it ages, corrodes, and accumulates damage; Part 180 sets the intervals at which it must be requalified or retired; without these requirements, a cylinder or cargo tank that passed factory tests decades ago could remain in service past the point of safe use
  • § 180.205 — General cylinder requalification: cylinders must be requalified by a Requalification Identification Number (RIN) holder — a facility registered with and audited by PHMSA; requalification includes visual external and internal inspection, hydrostatic pressure test, valve check, and verification of required markings
  • § 180.209 — Periodic requalification intervals (key types):
    • Standard industrial cylinders (DOT-3A, DOT-3AA): 12-year hydrostatic test; a "+" mark authorizes overfilling to 110% of marked pressure and extends the requalification period; a "★" mark permits indefinite requalification without the standard 12-year deadline if the cylinder passes each test
    • High-pressure specialty cylinders (DOT-4B, DOT-4BA, DOT-4BW): 5-year interval
    • Acetylene cylinders (DOT-8, DOT-8AL): 3-year interval because porous filler material complicates accurate pressure testing
    • Aluminum cylinders (DOT-3AL): 5-year interval for most, 12-year for certain rated service pressures
  • § 180.211 — Cylinder repair: DOT-4 series welded steel cylinders may be repaired by a RIN-holder following specific procedures; all other cylinder types must generally be condemned and rendered permanently unusable (drilled through the shell) if defective — field repair of seamless cylinders is prohibited
  • § 180.213 — Requalification markings: a requalified cylinder must be stamped with the RIN, month and year, and test type directly into the metal; paper labels or adhesive markings are not acceptable; marking must be legible at the time of each subsequent fill
  • § 180.215 — Records: RIN-holders must maintain records of each cylinder tested — identification, specification, test results, and date — for the service life of the cylinder; records must be available for PHMSA inspection or post-incident traceability
  • Subpart E — Cargo Tanks (§§ 180.401–180.417): highway tanker trucks used for bulk liquid hazmat must undergo annual external visual inspection and thickness measurement; internal visual inspection every 5 years (for most mild steel tanks); pressure test (50 psig or as specified) at 5-year intervals and after any structural repair; inspections must be performed by a Cargo Tank Facility (CTF) registered with PHMSA; a tank whose shell has thinned below the minimum design thickness must be removed from hazmat service regardless of its age
  • Subpart F — Tank Cars (§§ 180.501–180.517): railroad tank cars must satisfy both Part 179 design specifications and Part 180 maintenance requirements; periodic hydrostatic tests, valve inspections, and shell thickness checks are required at intervals keyed to the tank car specification; shops performing requalification must be approved by the Association of American Railroads (AAR) Tank Car Committee and registered with PHMSA

  The requalification system exists because aging packagings can fail with catastrophic results. A compressed gas cylinder that has been overfilled, corroded internally, or mechanically abused may rupture with explosive force. The RIN system ensures that only audited, registered facilities perform cylinder requalification — creating an accountability chain that allows PHMSA to trace any failed cylinder back to the facility that last certified it. For cargo tanks (tanker trucks), the CTF registration system performs the same function on the highway: every shop that signs off on a tanker inspection is accountable for that signature.

• 49 CFR Parts 105–110 — PHMSA procedures (registration, rulemaking, special permits, penalties, incident reporting). 49 CFR Part 107 — Hazardous Materials Program Procedures is the most consequential of these for regulated shippers and carriers:

  • Subpart B — Special Permits (§§ 107.101–107.127): a special permit authorizes a person, company, or industry group to transport hazardous materials in a manner that doesn't comply with the HMR if PHMSA determines the alternative provides equivalent safety; common uses include new packaging designs not yet in the HMR, innovative safety technologies, alternative testing methods, and emergency shipments; applications are submitted to PHMSA's Associate Administrator for Hazardous Materials Safety; PHMSA may grant emergency processing (24-hour response) when there is an imminent hazard and the alternative is demonstrably safe; permits may have party status — other companies can join an existing permit without filing a new application; party-status holders are bound by all permit conditions; permits are renewable annually; modification or termination is possible if safety concerns arise or the permittee violates conditions; all special permit documents are publicly available for inspection at PHMSA
  • Subpart C — Preemption (§§ 107.201–107.215): federal hazmat transportation law preempts any state or local requirement concerning transportation of hazardous materials if it is not substantively the same as the federal requirement or creates an unreasonable burden on interstate commerce; states may petition PHMSA for a preemption determination; states may also apply to maintain a preempted requirement if they can demonstrate it affords greater protection; this prevents a patchwork of state hazmat routing, packaging, and labeling requirements that would be impossible to comply with nationally
  • Subpart D — Enforcement (§§ 107.301–107.339): PHMSA investigators may conduct inspections and investigations; enforcement actions begin with either a warning letter (for minor violations), a ticket (for low-risk violations — civil penalty up to $10,000, paid or disputed within 45 days), or a Notice of Probable Violation (NOPV) for more serious violations; respondents have 30 days to admit the violation (and potentially negotiate a reduced penalty), submit an informal response with explanations, or request a formal hearing before an Administrative Law Judge; PHMSA may seek a compliance order requiring specific corrective action in addition to civil penalties; injunctive relief through federal district courts is available for imminent hazards
  • Subpart G — Annual Registration (§§ 107.601–107.620): shippers and carriers who transport certain large-quantity or high-risk hazmat shipments must register annually with PHMSA and pay a fee; registration is required for: highway route-controlled radioactive materials, >25 kg of Class 1.1/1.2/1.3 explosives, materials "extremely toxic by inhalation" (Hazard Zone A) in quantities >1 liter per package, bulk shipments in packagings >3,500 gallons capacity, and non-bulk shipments of 5,000+ pounds gross weight of a single hazard class requiring placarding; registration runs July 1 to June 30 (annual year); filing deadline is June 30; fees are $250/year for small businesses and nonprofits, $2,575/year for large entities; motor carriers must carry their Certificate of Registration in each truck cab; vessel operators must carry it aboard; failure to register is itself a violation subject to civil penalties; 3-year records retention required

• 49 CFR Part 130 — Oil Spill Prevention and Response Plans (20 sections across 3 subparts — PHMSA's spill prevention and response planning requirements for oil transported by highway motor vehicles and railroad tank cars):

  Part 130 is the non-pipeline complement to the EPA's Spill Prevention, Control, and Countermeasure (SPCC) rule (40 CFR Part 112) and PHMSA's pipeline response plan rule (49 CFR Part 194) — covering the modes that transport oil overland in tank trucks and rail tank cars. Subpart A covers both motor vehicles and rail; Subpart B covers basic spill response plans; Subpart C covers the more detailed Comprehensive Oil Spill Response Plans (COSRPs) required for railroads transporting oil in large quantities.

  • Subpart A — General (§§ 130.1–130.11): Part 130 applies to oil (any kind, including crude oil, petroleum products, vegetable oils, and animal fats) transported in quantities large enough to pose spill risk; shippers must provide carriers with documentation identifying the oil type and applicable response plan; emergency communication requirements (§ 130.11) ensure that carriers, shippers, and emergency responders can reach each other during a spill
  • Subpart B — Basic requirements (§§ 130.20–130.31): any motor carrier transporting a bulk oil shipment in a container with 3,500+ gallon capacity must have a basic spill response plan that identifies: who to notify in case of a spill (NRC, state agencies, local emergency responders); what immediate containment actions to take; what response equipment is available and where; the basic plan must be kept current and available to the driver
  • Subpart C — Comprehensive Oil Spill Response Plans for railroads (§§ 130.100–130.155): railroads that transport oil in quantities over 1 million gallons per year must develop, submit, and implement Comprehensive Oil Spill Response Plans (COSRPs); a COSRP must cover each response zone the railroad operates in — a geographic segment of the railroad's operations with a designated environmental sensitivity profile; requirements include: consistency with the National Contingency Plan (NCP) (40 CFR Part 300) (§ 130.110) and applicable Area Contingency Plans (§ 130.115); a complete information summary with worst-case discharge scenario, the amount of oil that could be released from a maximum-size train consist, and the nearest navigable waters; notification procedures (§ 130.125) identifying the National Response Center number and state agency contacts; response and mitigation procedures (§ 130.130) verifying that the railroad has contracted with private spill response contractors in each zone and can mobilize equipment within defined timeframes; training and drill programs (§§ 130.135–130.140) with annual table-top exercises and periodic equipment deployment drills

  The practical trigger: the 2013 Lac-Mégantic derailment in Quebec, Canada — in which a 74-car crude oil train derailed, killing 47 people and releasing 1.5 million gallons of Bakken crude — prompted the U.S. to strengthen its rail crude oil safety requirements dramatically. Part 130 COSRPs are now a central element of the enhanced crude-by-rail safety framework, alongside tank car standards (Part 179), routing requirements, and speed restrictions. Railroads operating in high-consequence areas (near populated areas, wetlands, water supplies, or environmentally sensitive zones) must demonstrate they have the contractor relationships and equipment pre-positioned to respond to a worst-case release scenario. Recent rulemaking: 85 FR 45013 (July 2020) updated COSRP requirements to align with EPA NCP revisions and strengthen response time requirements.

Pending Legislation (119th Congress)

• S 2975 (Sen. Cruz, R-TX) — PIPELINE Safety Act of 2025. Would modernize pipeline safety, raise PHMSA funding, and create a confidential industry data-sharing system to speed inspections. Status: In committee.
• HR 5368 (Rep. Strickland, D-WA) — Pipeline Safety Engagement Act of 2025. Would create an Office of Public Engagement at PHMSA to centralize pipeline safety outreach and public assistance. Status: In committee.
• HR 3948 (Rep. Brownley, D-CA) — Offshore Pipeline Safety Act. Would tighten offshore pipeline inspections, create per-mile owner fees, and order studies on pipeline removal risks. Status: Introduced.
• HR 6187 — Wojnovich Pipeline Safety Act of 2025. Would create a grant program, stronger public notices and testing, emergency alerts, large penalties, and a trust fund to modernize hazardous liquid pipeline safety. Status: Introduced.
• HR 7748 — Would enhance safety requirements for trains transporting hazardous materials. Status: Introduced.

Recent Developments

• The East Palestine, Ohio train derailment (2023) carrying hazardous materials intensified scrutiny of hazmat rail safety — the NTSB investigation drove new safety recommendations
• Lithium battery transportation regulations have been updated to address growing volumes and fire risks
• PHMSA has proposed updates to hazmat packaging standards and special permits processes
• International harmonization of hazmat regulations continues through the UN Recommendations on the Transport of Dangerous Goods
• Cybersecurity risks to hazmat transportation systems (pipeline SCADA, rail signaling) are an emerging concern