Armco is the name of the steel crash barriers commonly used alongside motorways and race tracks (above).

The name comes from the American Rolling Mill Company, which later became known as Armco and has since changed its name to AK Steel.

Armco has become a generic name for steel crash barriers, in the same way that Jeep and JCB have come to represent a whole class of products rather than just a single brand.

Armco barriers are effective in preventing vehicles from leaving the road or track, but because they deform only to a limited extent during a collision they can inflict serious damage to a vehicle in a major accident, potentially causing injury to the occupants. For this reason Armco is used in areas where there is limited space and the priority is to avoid vehicles leaving the road, such as in the central reservation of a motorway or dual carriageway road.

In common with other types of crash barrier, Armco barriers cannot function correctly if they are poorly installed and can even make an evolving accident worse. In motorsport, poorly installed crash barriers were implicated in a number of F1 fatalities in the early 1970s, and a similar issue appeared to contribute to Robert Kubica's crash on the Circuit of Andora rally in 2011.