High Risk, High Regulation: The Guide to Dangerous Goods by Rail

At 01:14 on 6 July 2013, a runaway train of 72 tank cars carrying Bakken crude oil crested a grade above the town of Lac-Mégantic, Québec, and accelerated to approximately 105 km/h before derailing in the centre of the downtown core. Sixty-three of the 72 DOT-111A tank cars ruptured on impact. The resulting fireball — fuelled by approximately 7.7 million litres of light crude oil — destroyed 40 buildings, killed 47 people, and contaminated the Chaudière River with an estimated 100,000 litres of hydrocarbons. The train had been left unattended on a grade by a single-person crew; the locomotive’s air brakes had leaked off overnight. Every element of the disaster — the inadequate tank car construction, the single-crew operating practice, the absence of mandatory handbrake requirements for unattended trains on grades, the routing of high-hazard crude through a populated town centre — was legal under the regulations in force that night. The Montreal, Maine and Atlantic Railway went bankrupt within weeks. Canada’s Transportation Safety Board issued 19 recommendations. The United States PHMSA issued emergency orders within days. And the global conversation about how dangerous goods move by rail, and under what regulatory framework, changed permanently.

What Are Dangerous Goods by Rail?

Dangerous goods — known as “hazardous materials” (hazmat) in North American regulatory practice — are substances or articles that, by virtue of their chemical, physical, or biological properties, pose a risk to human health, safety, property, or the environment during transport. The category is deliberately broad: it encompasses substances as different as compressed oxygen, radioactive medical isotopes, lithium-ion batteries, chlorine gas, and ammonium nitrate fertiliser. What they share is that their behaviour during an incident — fire, collision, derailment, or leakage — is materially different from general freight and requires specific emergency response, containment, and mitigation procedures.

The fundamental principle of dangerous goods regulation is that the hazard classification of a substance determines every subsequent decision: how it is packaged, what type of wagon or tank car carries it, how it is labelled and documented, where it is positioned in a train consist, whether it may pass through tunnels or enter classification yards, and what emergency procedures apply if something goes wrong. The classification is not a commercial or administrative category — it is an engineering and toxicological judgment that has direct consequences for infrastructure design, operational procedures, and emergency response capability.

The Global Regulatory Framework: RID, 49 CFR, and the UN Model Regulations

The transport of dangerous goods is regulated at three levels: international model regulations developed by the United Nations; regional instruments that transpose those models into binding law; and national enforcement frameworks. The UN Committee of Experts on the Transport of Dangerous Goods publishes the “Orange Book” (formally, the UN Recommendations on the Transport of Dangerous Goods — Model Regulations) on a biennial cycle. This document is not itself legally binding, but it provides the classification system, UN numbers, labelling requirements, and packaging specifications that underpin all modal-specific regulations worldwide.

RID — The European Rail Standard

The RID (Règlement concernant le transport International ferroviaire des marchandises Dangereuses — Regulations concerning the International Carriage of Dangerous Goods by Rail) is Appendix C to the Convention concerning International Carriage by Rail (COTIF), administered by the Intergovernmental Organisation for International Carriage by Rail (OTIF), headquartered in Bern, Switzerland. It applies to all 50 OTIF member states and is updated on a two-year cycle (odd years: 2023, 2025, etc.), with the current edition entering force on 1 January 2023. Within the European Union, RID is given direct legal effect by EU Directive 2008/68/EC on the inland transport of dangerous goods, which also covers road (ADR) and inland waterway (ADN) transport under a harmonised framework.

RID is structured in seven parts: Part 1 (General provisions), Part 2 (Classification), Part 3 (Dangerous Goods List — the reference table for all regulated substances), Part 4 (Packaging and tank provisions), Part 5 (Consignment procedures), Part 6 (Construction and testing requirements for packagings), and Part 7 (Provisions concerning the conditions of carriage, loading, unloading, and handling). Appendix B.1 covers the Uniform Rules for the use of wagons in international rail traffic and is cross-referenced extensively in Part 7.

49 CFR — The North American Framework

In the United States, the transport of hazardous materials by all modes — including rail — is governed by the Hazardous Materials Regulations (HMR) contained in Title 49 of the Code of Federal Regulations (49 CFR), Parts 171 through 180. The Pipeline and Hazardous Materials Safety Administration (PHMSA), within the Department of Transportation (DOT), is the primary rulemaking authority; the Federal Railroad Administration (FRA) is the primary enforcement authority for rail. Tank car construction standards are jointly governed by 49 CFR Part 179 and the Association of American Railroads (AAR) Manual of Standards and Recommended Practices, specifically Section C, Part III — Specification M-1002 for tank cars. In Canada, the equivalent framework is the Transportation of Dangerous Goods Act (TDGA) 1992 and its associated Regulations (TDG Regulations), administered by Transport Canada.

The Nine UN Hazard Classes: Classification and Railway Implications

All dangerous goods regulated under both RID and 49 CFR are assigned to one of nine primary UN hazard classes, with several classes subdivided into divisions. The class determines the type of hazard warning label (diamond-shaped placard), the packaging group (PG I = greatest hazard; PG II = medium; PG III = minor hazard), and the specific operational restrictions that apply during rail transport.

The Orange Plate System: Reading a Kemler Code

The orange-plate marking system — standardised under RID and the parallel ADR road regulation — provides a two-line code displayed on a rectangular orange reflective plate (40 cm × 30 cm) affixed to each dangerous goods wagon or tank. The system is designed for rapid identification by emergency responders without specialist chemical knowledge: the plate conveys the nature of the hazard and the identity of the substance in less than two seconds of visual inspection.

The top line carries the Hazard Identification Number (HIN), also known as the Kemler Code after its German originator. The HIN is a two- or three-digit code; each digit represents a primary hazard, and a doubled digit indicates that the hazard is intensified. A leading “X” indicates that the substance must not come into contact with water. The bottom line carries the four-digit UN number that uniquely identifies the substance in the UN Model Regulations list.

Tank Wagons: The P-Code and L-Code System (RID)

For liquids and gases transported in bulk — rather than in packagings — the wagon itself is the containment vessel, and its design is specified by a tank code under RID Part 4. The code communicates the construction standard, working pressure, lining material, and permitted filling ratio to infrastructure managers, yards, and emergency responders. Understanding tank codes is essential for train planners, as many routing decisions (tunnel categories, maximum speed through yards, barrier wagon requirements) depend on the tank code rather than the substance class alone.

The code structure for portable tanks and tank wagons is as follows: a letter indicating the tank type (L = liquid tank, P = pressure tank, G = gas tank), followed by digits indicating the minimum test pressure in bar (e.g., L4 = 4 bar, P22 = 22 bar), followed by letters indicating the filling and discharge provisions (e.g., BN = bottom opening not permitted for filling or discharge). An additional letter may indicate the lining or jacket (e.g., H = polyethylene-lined for acids; F = flame-proof). The full code L4BH, for example, means: liquid tank, 4 bar test pressure, no bottom opening permitted, inner lining required — the standard for many dilute acid shipments.

Operational Restrictions: Humps, Barrier Wagons, Tunnels, and Speed

Hump Shunting and Impact Restrictions

Classification yards sort wagons by pushing them over a raised “hump” and allowing gravity to propel individual wagons down inclines and into their designated sidings, where retarders control speed. The impact velocity between a rolling wagon and a stationary wagon at the end of a siding is typically 1.5–5 km/h. For most freight wagons, this is harmless. For dangerous goods wagons — particularly those carrying explosives (Class 1), organic peroxides requiring temperature control (Class 5.2), toxic gases (Class 2.3), and certain high-hazard Class 3 and Class 8 liquids — the impact, vibration, or shock of hump shunting may compromise containment integrity or initiate a reaction. RID Part 7 and 49 CFR Part 174 both specify substances for which hump shunting is prohibited; these wagons must be flat-switched (gravity or locomotive-propelled at walking pace with positive braking control) rather than humped. At a modern classification yard, wagon management systems automatically flag dangerous goods wagons as “no-hump” and divert them to flat-switch tracks.

Barrier Wagon Requirements

Barrier wagons (also called buffer wagons or separator wagons) are empty or loaded wagons of general freight interposed between dangerous goods wagons carrying incompatible substances, or between dangerous goods wagons and the locomotive. The purpose is to provide physical separation that reduces the risk of a chain reaction — fuel igniting an oxidiser, or a flammable liquid contacting an acid — in the event of a derailment. RID Table 7.5.3 specifies required separations between incompatible classes; the most common practical requirements are: explosives (Class 1) must be separated from flammable liquids (Class 3) by at least one barrier wagon; and Class 1.1/1.2 (high-hazard explosives) must be separated from the locomotive by a minimum of two barrier wagons. In North America, 49 CFR 174.81 governs compatibility and segregation requirements, with a similar table structure to RID 7.5.3.

Tunnel Restrictions (RID Tunnel Categories A–E)

Railway tunnels present a uniquely severe risk environment for dangerous goods incidents: a fire or toxic release inside a tunnel cannot be vented by natural convection, escape routes are limited, and emergency response times are dramatically longer than on open line. RID Part 8 establishes a five-category tunnel classification system (A through E), where A imposes no dangerous goods restrictions and E imposes the most severe. Each substance in the RID dangerous goods list carries a tunnel restriction code; the infrastructure manager assigns a tunnel category to each tunnel on its network, and the train operator must verify that the tunnel category permits the transport of the goods in question.

The Dangerous Goods Safety Adviser (DGSA)

Under RID Section 1.8.3 (and the parallel ADR provision for road), any undertaking — railway operator, shunting company, terminal operator, or shipper — whose activities include the carriage, loading, unloading, or filling of dangerous goods must appoint at least one Dangerous Goods Safety Adviser (DGSA). The DGSA is a qualified individual responsible for advising the undertaking on compliance with dangerous goods regulations, preparing an annual report on dangerous goods activities, and conducting an internal investigation following any dangerous goods incident. The DGSA is not the person who handles the goods daily — they are a compliance function, analogous to a company safety officer — but they hold personal liability for the accuracy of their advice.

DGSA qualification requires passing a competent authority examination covering the relevant modal regulations (RID for rail) and obtaining a certificate of training (valid five years, renewable by examination or by demonstrating continuing professional development). In the United Kingdom, the DGSA examination is administered by bodies approved by the Department for Transport. In Germany, the Industrie- und Handelskammern (IHK) administer the qualification. There is no equivalent mandatory role in North American federal hazmat regulation, though the Emergency Response Guidebook (ERG), published biennially by PHMSA and Transport Canada, serves a broadly similar first-responder orientation function.

Landmark Incidents That Shaped Modern Regulation

Lac-Mégantic, Québec, Canada — 6 July 2013

The most lethal North American rail accident of the 21st century. A Montreal, Maine and Atlantic Railway (MMA) train of 72 DOT-111A tank cars loaded with Bakken crude oil (UN 1267, Class 3, PG I) was left unattended on a grade at Nantes, Québec, overnight. The lead locomotive’s air brakes had been applied to hold the train, but a fire in the locomotive’s engine — extinguished by a local fire brigade during the night — led to the locomotive being shut down. Without the running engine maintaining brake pipe pressure, the air brakes gradually leaked off. At approximately 01:15 on 6 July 2013, the train began rolling uncontrolled down a 1.2% grade for approximately 11 km, reaching an estimated 105 km/h before derailing at a curve in the centre of Lac-Mégantic. 63 of 72 tank cars ruptured; the resulting fire burned for 36 hours. The human toll was 47 dead — more than half the population of the town’s downtown core. Key regulatory changes that followed: mandatory handbrake requirements for unattended trains on grades (49 CFR 232.103); replacement of DOT-111 cars carrying Class 3 PG I/II flammables with DOT-117 (new construction) or DOT-117R (retrofit), with full fleet replacement deadline of 2020–2025 by shipment type; and the introduction of High Hazard Flammable Train (HHFT) regulations requiring enhanced tank car standards, reduced speed, and route analysis for trains of 20+ cars of Class 3 flammable liquids.

East Palestine, Ohio, USA — 3 February 2023

A 150-car Norfolk Southern freight train derailed at East Palestine, Ohio, due to a failed bearing on a wagon axle. Eleven of the derailed wagons carried vinyl chloride monomer (VCM, UN 1086, Class 2.1 — flammable gas). Fearing a BLEVE (Boiling Liquid Expanding Vapour Explosion) in the five VCM pressure tank cars after the derailment fire, emergency responders conducted a controlled venting and ignition of the VCM — a “vent and burn” procedure — on 6 February 2023. The procedure prevented a potential explosion but released hydrogen chloride (HCl) and phosgene as combustion products, contaminating surrounding soil and waterways with chlorinated compounds. The disaster renewed debate about hotbox detector spacing standards (the failed bearing had passed two detectors without triggering shutdown thresholds), the vent-and-burn decision-making process, and whether the 2017 rollback of ECP (Electronically Controlled Pneumatic) brake requirements — which the Obama administration had mandated and the Trump administration reversed — contributed to the severity of the derailment.

Viareggio, Italy — 29 June 2009

A freight train carrying liquefied petroleum gas (LPG) in Type P pressure wagons derailed at Viareggio station, Italy, due to a broken axle on a leased tank wagon. The ruptured tank released LPG, which ignited immediately upon contact with the hot axle and spreading across the street adjacent to the station. The fireball reached nearby apartment buildings; 32 people died and a further 26 were seriously injured. Subsequent investigation found that the axle had developed a fatigue crack that had not been detected during routine inspection, partly because inspection intervals for leased wagons crossing multiple national jurisdictions were not coordinated between lessors, lessees, and national safety authorities. The accident accelerated EU implementation of the European Railway Agency’s (now ERA’s) common approach to axle inspection intervals and led to mandatory ultrasonic axle inspection requirements codified in EN 13260 and TSI Freight Wagons.

Frequently Asked Questions

1. What exactly is a Kemler Code and how does a firefighter use it at an incident scene?

The Kemler Code — named after the German chemist and transport safety expert who proposed the system in the 1960s — is the two- or three-digit Hazard Identification Number (HIN) displayed on the upper half of the orange plate affixed to a dangerous goods wagon. It is a shorthand summary of the primary and secondary hazards of the substance in the wagon, using a single-digit coding scheme (2 = gas emission, 3 = flammability, 6 = toxicity, 8 = corrosivity, etc.) where a doubled digit indicates the hazard is intensified. The code 33, for example, means “highly flammable liquid” — the double 3 intensifying the basic flammability hazard of a single 3. The code 268 means gas (2) with toxic (6) and corrosive (8) properties — the hazard profile of chlorine.

At an incident scene, a trained first responder reads the orange plate from a safe distance using binoculars if necessary. The HIN on the top line immediately tells the responder whether to prioritise fire suppression (3x codes), decontamination and evacuation (6x codes), or explosion standoff (1x codes, also identifiable by the Class 1 diamond placard). The UN number on the bottom line then allows the responder to cross-reference the specific substance in the Emergency Response Guidebook (North America) or the emergency information system (TUIS in Germany, CANUTEC in Canada, CHEMTREC in USA) to obtain precise spill containment distances, protective equipment requirements, and first aid protocols. The beauty of the Kemler system is that it functions without any communication infrastructure — no internet, no radio contact — which is precisely the condition that pertains immediately after a major derailment.

2. Why are Class 1 explosives banned from hump shunting, and what happens if the rule is violated?

The hump shunting prohibition for Class 1 explosives exists because primary explosives — substances sensitive to shock, friction, or heat — can be initiated by the impact energy of a wagon rolling into a siding and striking a stationary wagon. The kinetic energy of a 60-tonne loaded wagon travelling at 5 km/h is approximately 58,000 joules at impact. While most modern packaged explosives are desensitised and require a booster charge rather than mere mechanical shock to detonate, the regulatory prohibition applies to the entire class because (a) the consequences of a Class 1 detonation in a classification yard are catastrophic and irreversible, and (b) it is impractical to verify the sensitivity characteristics of packaged commercial explosives at the yard without opening the packages. The 2004 Ryongchon railway disaster in North Korea — though caused by static electricity igniting ammonium nitrate during shunting rather than hump impact — killed an estimated 160 people and devastated a 4 km² area, illustrating the scale of consequences when energetic materials are involved in shunting incidents.

Violations of hump shunting prohibitions in European systems are addressed through the train documentation system: each wagon’s consignment note specifies its UN number and Class, and the yard’s wagon management system — cross-referencing RID 7.1.6 — should automatically route prohibited wagons to flat-switch tracks. If a yard operator overrides the system and humps a Class 1 wagon, the consequence — absent an incident — is typically a regulatory fine and a formal investigation by the national safety authority (NSA). Following an incident, the criminal liability framework applies; in the EU, rail operators can face prosecution under national criminal law for breach of RID provisions that caused death or injury. Germany’s StGB §315 (endangering rail traffic) has been used in dangerous goods cases.

3. Why was the DOT-111 tank car considered inadequate after Lac-Mégantic, and what makes the DOT-117 different?

The DOT-111A tank car — the workhorse of North American liquid bulk transport for more than four decades — was designed to carry commodity chemicals, corn syrup, and vegetable oils, not crude oil at high vapour pressure. Its shell is typically constructed of 7/16-inch (11 mm) steel, without a jacket or thermal insulation layer; its top fittings — loading dome, safety valve, pressure relief device — are exposed and unprotected by a head shield; and its bottom outlet valve — used in many installations for loading and unloading — projects below the car body, making it vulnerable to puncture during a derailment when the car rolls or strikes track or other cars. In a derailment at speed, the DOT-111A’s thin shell is prone to puncture by wheel flanges, rail ends, and other structural elements; testing by the Transportation Safety Board of Canada found that DOT-111 cars at Lac-Mégantic began to fail at impact speeds as low as 8–12 km/h.

The DOT-117, mandated by PHMSA’s final rule of May 2015 (HM-251) for new construction in flammable liquid service, addresses these failure modes with a thicker shell (9/16-inch or 14 mm steel minimum), a full-height half-inch steel head shield protecting the end fittings, a thermal protection system (jacket with ceramic insulation achieving 100-minute fire resistance), and — critically — a recessed or non-bottom-outlet design on many variants that eliminates the exposed valve projection. The DOT-117R retrofit standard applied the head shield and thermal protection jacket to existing DOT-111 cars deemed structurally adequate. PHMSA established phased retirement deadlines for un-retrofitted DOT-111 cars: Class 3 PG I flammable liquids (including Bakken crude) in non-enhanced cars were prohibited from 2018; full fleet transition was mandated by 2025 for most service categories. The cost of fleet-wide retrofitting or replacement was estimated at $3–5 billion across the North American tank car fleet.

4. How does the tunnel category system work in practice, and who decides what category a tunnel receives?

Tunnel categorisation under RID Part 8 is the responsibility of the infrastructure manager — the entity that owns and operates the railway infrastructure — in consultation with the competent authority (usually the national rail safety regulator). The categorisation process is a risk assessment that considers the tunnel length (longer tunnels have less natural ventilation and longer emergency access times), the proximity of the tunnel portals to populated areas, the availability of cross-passages and emergency exits within the tunnel, the ventilation system capacity, and the rescue and emergency response resources available in the vicinity. A short tunnel of 500 m in a rural area with no alternative routing might warrant only Category B, while a long urban tunnel of 10 km under a city centre — where a major toxic release could affect hundreds of thousands of people — might warrant Category D or E.

Once categorised, the tunnel’s restriction code is published in the infrastructure manager’s Network Statement (the document that all train operators must consult before requesting train paths), and is also encoded in any train planning software used by freight operators. A train operator planning a route carrying, say, chlorine (UN 1017, restriction code B/D — prohibited from Category D and E tunnels) must verify that no tunnel on the planned route carries a Category D or E designation. In practice, this means that certain dangerous goods flows are routed on specific corridors that avoid restricted tunnels — which may add hundreds of kilometres to the journey compared to the most direct route. The Channel Tunnel between the UK and France is categorised as “B” — permitting most dangerous goods except the highest-hazard explosives and very large quantities of toxic gases — and has specific additional protocols including mandatory monitoring of tank wagons in transit and emergency response pre-positioning at both portals.

5. What is the role of the DGSA, and can a company face criminal liability if its DGSA gives incorrect advice?

The Dangerous Goods Safety Adviser (DGSA) is a formally qualified individual appointed by any undertaking whose activities involve the carriage, loading, unloading, or filling of dangerous goods under RID or ADR. The DGSA’s statutory duties, set out in RID 1.8.3.3, include: monitoring compliance with dangerous goods regulations; advising the undertaking on the transport of dangerous goods; preparing an annual report on the undertaking’s dangerous goods activities; investigating accidents and incidents involving dangerous goods; and implementing appropriate measures to prevent recurrence. The DGSA must hold a valid certificate of training specific to the relevant mode (rail, road, or both) issued by the national competent authority, renewed every five years.

The question of criminal liability is legally complex and varies by jurisdiction. The DGSA is not personally liable for every regulatory breach that occurs within the undertaking — they are an adviser, not the operational decision-maker. However, under EU criminal law frameworks and national implementations of RID’s competent authority provisions, a DGSA who knowingly provides incorrect advice that leads to a dangerous goods incident causing death, injury, or significant environmental damage can face prosecution under the applicable national criminal law (professional negligence, gross negligence manslaughter, or equivalent). In Germany, the administrative fine framework under §37 GGBefG imposes personal fines on DGSAs for regulatory violations up to €50,000. In the UK, the Health and Safety at Work Act 1974 and the Management of Health and Safety at Work Regulations 1999 can extend liability to individual advisers whose failures contribute to foreseeable harm. The practical consequence is that experienced DGSAs carry professional indemnity insurance and maintain meticulous written records of the advice they provide, so that any subsequent incident can be assessed against the documented basis of their recommendations.