Diesel locomotives spotted leading passangers trains in Béni-Mered and Chiffa.

Filmed by Abdelaziz AOUALI
Locomotive in the first and second clip: rehabilitated EMD GT26CW class 060DL12.
Locomotive in the third clip: EMD GT36HCW class 060DS07.

The origin of this system of classes is french and it still be used in Algeria since 1963 and here is what it means:
060: six axles that have traction motors.
040: four axles that have traction motors.
D: Diesel
W stands for "1435mm standard guage".
Y stands for "1055mm narrow guage".
Any letter of the alphabet ( for example L or S): alphabetical order of locomotives.
And the last two digits refer to the number of that locomotive.

Here are all locomotive classes in Alphabetical order since 1950s:
060DB : I have no information about that type.
060DC : Alsthom class CC65000.
060DD : EMD GT26CW (No dynamic brakes, no head-end power).
060DF : EMD GT26CW (With dynamic brakes, no head-end power).
060DG : EMD GT26CW (With dynamic brakes and high hood, with head end power).
060DH : EMD GT22CW (WIth dynamic brakes and head-end power).
060DJ : GE U18C (Used for shunting, no head-end power).
060WDK : EMD GL18M (Used for shunting, no head-end power).
040YDA : EMD GL18M (No head-end power).
060DL : EMD GT26CW (Same as 060DF but with head-end power).
060YDD : EMD GT18 LC2M (No head-end power, has turbocharger).
060DM : EMD GT26 HCW 2A (With dynamic brakes and head-end power).
060DP : EMD GT26 HCW 2A (Same as 060DM).
040DH : EMD GL18B (Used for shunting, no head-end power, no turbo).
040DJ : EMD GL18B (same as 040DH).
060DR : EMD GT36CW (With dynamic brakes and no head-end power).
060DS : EMD GT36HCW (Same as 060DR but has head-end power).
060DT : EMD GT46AC (No head-end power, uses alternative current).

In case you are wondering about 060DA, it was a class of Diesel locomotives in France (SNCF), shortly after that they stopped using this system of classes and they started to use it in French Algeria (before 1962 SNCFA).