The locomotive halves of a double locomotive can be provided with couplings that can only be separated in the workshop, but also with normal pulling and pushing devices. The equipment of the locomotive halves can be the same or different. If the locomotive halves have the same structure and are equipped with standard rail couplings on both sides, individual locomotive halves can also be used for operational purposes. Double locomotives with different locomotive halves can only be operated together, because otherwise some of the equipment required to operate the double locomotive would be missing.
Double locomotives are mostly used where the pulling power of a single locomotive would be insufficient. By saving two driver's cabs compared to a double traction , maintenance and procurement costs can be saved.
By far the largest number of double locomotives are used by the railways of the CIS countries . The direct current locomotive ВЛ10 , alternating current locomotive ВЛ80 and the diesel locomotives ТЭ2 , as well as 2ТЭ116 are selected as examples from the inventory comprising several thousand locomotives . The locomotives come from various factories, such as the Luhansk Locomotive Factory , the Kharkov Railway Factory or the Novocherkassk Electric Locomotive Factory .
In Switzerland have been series SBB Ae 8/14 and BLS Ae 8/8 developed. The Ae 8/14 was ahead of its time, because the couplings of the time did not withstand the high pulling forces of the double locomotive.
In Italy there are several series of electric double locomotives, such as the FS E.656 series .
- Locomotives with normal pulling and pushing devices between the sections: MTAB IORE , ВЛ80 , ВЛ10
- Locomotives with close couplings that are disconnected in the workshop: Ae 8/14 , BLS Ae 8/8 , 2ТЭ116
- Locomotives with the same locomotive halves: IORE , ВЛ80
- Fairlie : articulated locomotive that is largely symmetrical in the longitudinal direction
- Prussian EV 1/2 and Prussian EV 3/4 Altona
- DR series E 95
- SJ Dm
- SJ Dm3
- Wehrmacht locomotive D 311
- CFR series DE 241
- Karl Gerhard Baur: Bogies - Bogies . EK-Verlag, Freiburg i. B. 2006, ISBN 3-88255-147-X