MM&A Oil Train Tank Cars of Flawed Design

An article by David Crary of the AP/Kennebec Journal regarding the runaway MM&A oil train that crashed in Canada had a rather interesting paragraph:

The tanker cars involved in the crash were the DOT-111 type — a staple of the American freight rail fleet whose flaws have been noted as far back as a 1991 safety study. Experts say the DOT-111's steel shell is so thin that it is prone to puncture in an accident, potentially spilling cargo that can catch fire, explode or contaminate the environment.