Why do first responders rely so heavily on the four-digit identification number displayed on a hazmat shipment, rather than just the placard's hazard class symbol?

Question

Accepted Answer

The ID number lets them look up the specific material in the Emergency Response Guidebook (ERG) to get a guide number with material-specific response actions, not just the general hazard class

Answer

The ID number tells responders exactly which trucking company owns the load, which is their main concern during a spill

Answer

The placard symbol alone already gives responders every detail they need, so the ID number is mostly redundant paperwork

Answer

The ID number is only used for billing and insurance purposes after an incident, not during active emergency response