Shit happens! Trains derail, planes crash, cars and trucks get in accidents. Whattaya want? A moratorium on transporting anything toxic from one place to another? Four-car full-surround police escorts for every vehicle carrying hazardous cargo? How about invisible force fields around FedEx vans that repel red-light-running idiots? Sounds to me like every reasonable precaution was taken. If the containers the stuff was in are designed to withstand plane crashes I doubt a fender-bender is gonna wipe out half of Canada.

Okay... Maybe, just maybe, it might be a good idea to require that the vehicles used to transport certain toxic materials in urban areas be more like armored cars than regular delivery vans. Vans do have a pretty high center of gravity and are more prone to tipping over in crashes. It wouldn't keep idiots from running into them, but it'd make the accident less serious from the cargo's point of view.