To learn how the mod system works, I created this experimental new configuration for the default Citybus that adds a hybrid drivetrain similar to the hybrid buses found in larger cities like Chicago and NYC. This configuration includes a CVT transmission, boosted torque ahead of the torque converter (to simulate the electric component of the hybrid powertrain), and "regenerative braking" which slows down the vehicle when the throttle pedal is released (which, on a real hybrid bus, captures kinetic energy into the battery and reduces wear-and-tear on the air brake system).
This configuration is especially great on the "West Coast" map, as the increased torque helps when climbing the steep city inclines, and the regenerative braking likewise helps when descending these inclines.
There is a pre-made "citybus_hybrid" configuration, or you can change an existing configuration to hybrid by changing the engine option:
The hybrid system will technically work with an automatic transmission, but a CVT will yield the best results. It is default with the hybrid engine.
Beta Citybus Hybrid Drivetrain 1.2
A custom configuration of the City Bus that adds a "hybrid" drivetrain