Share of recoverable energy:

Share of recoverable energy heavily depends on speed and stopping pattern.

The following values are typical (referring to total energy demand) for different operation types

Main lines: 15%

Regional lines: 35 %

Suburban lines: 45%

Freight lines: 20%

The recovery rate actually reached in operation only exploits a part of this potential. This is due to several reasons:

• Efficiency of backwards power train: The recoverable energy can never be fully regenerated due to losses in backwards power train. Backwards efficiency is comparable to traction efficiency (~ 90%).
• Receptivity of catenary: The supply system may be „non-receptive“ because no other train is close enough to use it. In DC systems, this is frequently the case (cf. General criteria – barriers).
• Braking power: Many times the electric braking power is not sufficient and blended braking (cf. Description) is applied. Especially in freight operation, the electric brakes are usually insufficient for braking the entire train.

There is little (if any) quantitative data on these effects. The following table gives some estimates (!) for DC systems. Since the main obstacle is limited receptivity of catenary, the table gives the potential to be exploited with additional technologies (cf. General criteria – success factors) and the potential to be exploited without additional technologies:

	Theoretical potential	Correction due to traction efficiency	Correction due to blended braking	Potential if additional technologies are used	Correction due to non-receptive catenary	Potential without additional technology
Main lines	15%	0,9	0,8	11%	0,2	2%
Regional lines	35%	0,9	0,8	25%	0,4	10%
Local lines	45%	0,9	0,8	32%	0,5	16%
Freight lines	20%	0,9	0,5	14%	0,2	3%

Source: IZT

A part of the potential given in the last column is already exploited at present. So the remaining potential without additional technology will be around 1 - 5%. If innovative technology (cf. General criteria – success factors) is implemented, there is a saving potential of 5 – 20 % depending on the specific situation.