Powered by an MGO V16BSHR diesel engine developing 1,030 kW (1,380 hp), they had a maximum speed of 120 km/h (75 mph).

Though designed as a mixed traffic locomotive, they had no provision for train heating and could be seen working with boiler vans on passenger services.

With the general introduction of electric train heating they were relegated to freight work.

[2] Between 1985 and 1989, 34 locomotives were regeared for higher tractive effort and designated as Class BB 66700.

[3] From 2004 some 91 members of the class were rebuilt with new MTU engines and reclassified as BB 69200.