Accident involving high consequence dangerous goods
| Impact | 5 |
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| 3 |
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| 2 |
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| 1 |
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5 |
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| ID | 20 |
|---|---|
| Risk theme | Accidents and system failures |
Impact & Likelihood
| 5 | Catastrophic |
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| 4 | Significant |
| 3 | Moderate |
| 2 | Limited |
| 1 | Minor |
| 5 | >25% |
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| 4 | 5-25% |
| 3 | 1-5% |
| 2 | 0.2-1% |
| 1 | <0.2% |
Background
High-consequence dangerous goods may include corrosive, flammable, explosive, oxidising or spontaneously combustible substances. These inherent properties mean that an accident involving high-consequence dangerous goods could have serious impacts, such as mass casualties or destruction to buildings. However, there are regulations in place (the Carriage of Dangerous Goods and Use of Transportable Pressure Equipment Regulations 2009) to ensure that these substances are transported safely and securely so that accidents like the reasonable worst-case scenario below are unlikely to happen.
The regulations require, among other things, that drivers of dangerous goods vehicles are trained in the hazards presented by the loads they are carrying and what to do in the event of an accident. Such training is examined and evidenced by an additional driving licence specifically permitting the driver to carry such loads. Additionally, each undertaking involved in the consigning, carriage, or the related packing, loading, filling or unloading of dangerous goods is required to employ the services of a dangerous goods safety adviser. The adviser is responsible for helping to prevent the risks inherent in such activities with regards to persons, property or the environment. Further, it is a requirement that such dangerous goods are identified by appropriate placarding of the vehicles, highlighting the type of dangerous goods carried.
Scenario
The reasonable worst-case scenario assumes that a single road tanker containing high-consequence dangerous goods is involved in an accident, which results in a fire or explosion in an urban area. This would likely lead to road closures of several days, significant local infrastructure damage (road, buildings and bridges), and as a consequence, alternative routing and evacuation of surrounding areas.
Depending on the substance there could also be a risk to the environment, but assuming most of the substance is consumed in the fire, risk of entry into water courses would be minimised. There would also be a small number of casualties and fatalities. The types of substances that could be involved include flammable gases or liquids, substances liable to spontaneous combustion, ammonium nitrate and corrosive substances.
Key assumptions
It is assumed that the accident would occur in an urban area on a motorway or dual carriageway and impact housing and other infrastructure nearby. It is also assumed that the vehicle is carrying a full load of dangerous goods meeting the definition of high-consequence dangerous goods.
Variations
A less-impactful variation could see an accident in a rural area or with less dangerous goods carried, while a more impactful but significantly less likely variation could see a malicious incident involving more than one high-consequence dangerous goods vehicle.
Response capability requirements
Depending on the substance carried (for example corrosive substances), decontamination may be necessary. There may also be a need for some follow-up communications with the local area regarding possible measures to limit impact from any future accidents.
Recovery
It would take several months to rebuild or repair damage to buildings and infrastructure. If the accident investigation demonstrates that the failure of the tanker was the cause, it could lead to a period of adjustment to vehicle manufacturing requirements and international regime amendments for the transport of dangerous goods.