Failed or Absent Defences » LTA vehicle proximity control

47Non-Flameproof Diesel Vehicles Entering An Explosion Risk Zone 1

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Brief Description of Incident/Accident & Description of Consequences/Outcomes:

A non-flameproof diesel powered vehicle in an underground coal mine was driven into an Explosion Risk Zone 1 (where methane levels can range up to 2%). To prevent these vehicles entering such hazardous areas, they are equipped with a radio system that responds to a series of 'tags' mounted on the walls of the underground roadways. The 1st tag triggers a warning in the vehicle's cabin; the 2nd tag triggers an enhanced warning, while the 3rd tag shuts the vehicle down altogether. However, this particular vehicle was driven through the two warning tags and one shutdown tag without either the two warnings being initiated or the vehicle being shutdown by the 3rd tag!

Identified Root Causes:

Many of the vehicles' radio receiver aerials had been damaged since their introduction, and had been relocated from the roof areas to less damage prone areas of the vehicles. Radios had also been deliberately slightly desensitised to prevent nuisance tripping remote from the tags. As a result, if driven at maximum allowable speed on the far side of the roadway from the tags, the radio receivers sometimes did not activate the alarm or trip signals.

Energy Type(s) Involved:

Non-flameproof equipment entering an Explosion Risk Zone 1, where the non-flameproof vehicle might ignite methane gas in the mine atmosphere.

Equipment Type(s):

Non-flameproof Diesel Vehicle

Root & Contributing Cause(s):

LTA risk assessment

LTA safety device operation

LTA vehicle proximity

Stated or Potential Consequence(s):

Potential Multiple Fatalities

Preventative/Recommended/Accepted Steps of Risk Mitigation, Points of Interest:

It is recommended that a realistic test of the full system be carried out at regular intervals, in an underground roadway, under strict environmental conditions and management controls, and remote from hazardous areas. This "real" test should consist of driving the vehicle at maximum permissible speed through all the tags and recording the results. Issues such as damage to aerials should be specifically addressed during routine visual inspections of the vehicles.


Queensland Government Department of Employment, Economic Development and Innovation (DEEDI)


Here are the results.


Reference Type:

Significant Incident Report #59

Mine Type:

Underground Mine > Underground Coal Mine


Chemical > Gas





Australia, Queensland

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