They can also help prevent collapse of the roof in the event of a vehicle rollover.
The soft shoulders consisted of gravel with a sharp slope which was blamed for facilitating vehicle rollovers.
The 103 deaths attributed to defective Firestone tires have galvanized Congress to tackle the larger problem of vehicle rollovers.
But safety options are all the rage these days as the industry tries to capitalize on growing concerns about traffic, vehicle rollovers and tire recalls.
The department estimates that 228,000 vehicle rollovers occur a year.
Two soldiers were killed late Sunday in a vehicle rollover near Tal Afar.
On her husband's second tour to Iraq, in 2004, he was severely wounded in a vehicle rollover.
While they are not designed as rollbars, cargo barriers can also help prevent the collapse of a vehicle roof in vehicle rollovers.
The Times's analysis found that a vehicle rollover was the first thing that went wrong in 4,125 of the 10,657 rollover deaths last year.
"The increasing problem with vehicle rollovers has moved this issue to the small group of top agency priorities," he said.