This mod makes the Scania retarder and engine brake behave in a more realistic and progressive way.

In the vanilla game, the retarder works as follows:

Stage 1: 20% Retarder
Stage 2: 40% Retarder
Stage 3: 60% Retarder
Stage 4: 80% Retarder
Stage 5: 100% Retarder + 100% Engine Brake + Automatic downshifting to increase engine RPM

This mod changes the braking logic to:

Stage 1: 20% Retarder + 25% Engine Brake
Stage 2: 40% Retarder + 50% Engine Brake
Stage 3: 60% Retarder + 70% Engine Brake + Automatic downshifting to increase engine RPM
Stage 4: 80% Retarder + 90% Engine Brake + Automatic downshifting to increase engine RPM
Stage 5: 100% Retarder + 100% Engine Brake + Automatic downshifting to increase engine RPM

Credits:
Tiago Lanzarini