Road collision involving a LH2 trailer

A liquid hydrogen trailer stopped on highway due to traffic accident ahead. A second vehicle struck the trailer in rear at a high rate of speed, causing it to crash into another vehicle ahead. The vehicle which caused the incident damaged the rear cabinet of the trailer, so that the pressure control valve system, located there, was destroyed. The burst disc activated and the escaping hydrogen took fire engulfing the other vehicle, witch was completely destroyed. .
The trailer had a capacity of 13000 gallons (3800 kg) of LH2. The quantity released was 3000 gallons (780 kg).
The emergency operation lasted 17 hours (another source mentioned that the venting of the hydrogen release lasted 30 hours), during which the fire fighters kept the LH2 tank cooled.

The INITIAL CAUSE was collision.
the ROOT CAUSE is attributed generically to a human error (wrong manoeuvre).
A CONTRIBUTING CAUSE was the abnormal condition on the highway, due to the traffic jam caused by a previous incident ahead.
The safety system of the LH2 tanker functioned as designed.

vacuum thermal insulation; burst disc

A multiple crash happened before the release.

A fatality due to the crash. The traffic was disturbed for about 27 hours.
Pieces of the truck that hit the LH2 tanker were fused into the road by the high temperatures. That section of pavement had to be cut out and replaced before traffic could flow.

Fire fighters from 15 different local stations intervened. A 300-foot “safety zone” was established around the burning tanker, closing both lanes.
Live video was sent from the scene to company representatives showing the conditions of their vehicle and the fire behaviour emanating from their vessel. After several calls, the firefighters decided that the safest way to deal with the escaping gas was to allow it to burn, while at the same time keeping the tank cool. Initially, fire crews attacked the fire with water and foam, but quickly pumped their tanks dry. To be able to continue the cooling, firefighters set up remote nozzles that sprayed 25,000 gallons of water per hour on the tank for 17 hours. A total of 455,200 gallons of water was trucked from a hydrant, where it was pumped down as many as 1,000 feet of hose to the remote nozzles.
The release of 3000 gallons of hydrogen lasted 30 hours.
The company dispatched later a semi tanker loaded with helium, which was pumped into the damaged tanker. It displaced any possible oxygen left inside the tank, preventing combustion.

The vacuum between the internal and the external shell of the tank, which guarantees the thermal insulation required to keep the hydrogen below its liquefaction temperature, was damaged by the impact. The increase of pressure activated the burst disc releasing the hydrogen. Despite the consequent hydrogen flame, which eventually burnt out completely the other vehicle, the hydrogen vented in controlled way. The mitigating measures in place on the Liquid hydrogen tank worked as designed.