The recommendations, posted on the department's website Wednesday, outline a host of new regulations aimed at making the continent's rail infrastructure safer.
The rules come in the wake of several high-profile derailments in the past year, including one in Lac-Megantic, Que., in 2013 in which 47 people died.
DOT-111 rail cars were used in that disaster, and accident investigators have complained for decades that the cars are too easily punctured or ruptured when derailed, spilling their contents.
The new U.S. rules would require that all DOT-111 rail cars be retrofitted or removed from service soon, and replaced within two years with rail cars with thicker walls.
There's also a proposal to introduce a speed limit of 70 km/h near urban areas, until the old rail cars can be removed from service or replaced.
The rules are now subject to a 60-day public comment period.