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General information
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Description
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Safety requires a limitation of the permissible longitudinal force exerted on the locomotive by the following cars. If too much braking power is supplied by the locomotive, the heavy freight cars exert critical forces on the braking locomotive which lead to dangerous lateral forces in curves. Therefore maximum longitudinal forces are defined limiting the use of dynamic brakes. In many cases, this is a limitation for regenerative braking since in loco-hauled stock the only powered axles are located in the locomotive. Therefore these limitation values can restrict the use of dynamic brakes in situations where adhesion would still allow for it. In most countries, the limit values do not depend on the individual train mass. Instead, the “worst case” (e.g. heavy freight train) is taken to define the limit value for all trains irrespective of their mass (usually 150 kN). A more differentiated concept for these limit values would increase the recuperation potential in lighter trains (light freight trains or loco-hauled passenger stock). SBB has introduced such a concept (cf. General criteria - Example). |
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General criteria
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Status of development: in use |
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Used in Switzerland. |
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Time horizon for broad application: in < 2 years |
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(no details available) |
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Expected technological development: not applicable |
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Concept is not technological. |
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Motivation:
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Energy saving through increased recuperation |
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Benefits (other than environmental): small |
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Less wear of brakes through increased use of regenerative braking. |
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Barriers: medium |
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Safety The limitation of longitudinal forces is relevant for derailment prevention and therefore very safety critical. A modification of the regulations would require extensive safety audits. |
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Success factors:
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(no details available) |
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Applicability for railway segments: high |
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Type of traction: electric - DC, electric - AC
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Type of transportation: passenger - main lines, passenger - high speed, passenger - regional lines, passenger - suburban lines, freight
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Modified limit values for permissible longitudinal forces in the train would obviously affect all trains but the changes would be relevant only for loco-hauled stock since MUs have driven axles along the entire train. From the point of view of energy efficiency, the measure is only interesting for electric stock. |
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Grade of diffusion into railway markets:
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Diffusion into relevant segment of fleet: not applicable |
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Share of newly purchased stock: not applicable |
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(no details available) |
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Market potential (railways): not applicable |
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(no details available) |
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Example:
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SBB Swiss SBB have introduced a differentiated concept for the limitation of longitudinal forces. Whereas most railways use 150 kN for all trains, SBB have increased the permissible forces to 240 kN for most trains with some restrictions (to 150 kN) for some freight trains. |
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Environmental criteria
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Impacts on energy efficiency:
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Energy efficiency potential for single vehicle: (no data) |
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Energy efficiency potential throughout fleet: (no data) |
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It is difficult to assess the energy efficiency effect of modified regulations for longitudinal train forces. Influencing factors are: - The share of trains affected by such the modification
- Other limitations to an increased use of regenerative brakes (braking power, adhesion etc.)
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Other environmental impacts: neutral |
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Economic criteria
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Vehicle - fix costs: (no data) |
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(no details available) |
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Vehicle - running costs: minor reduction |
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(no details available) |
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Infrastructure - fix costs: none |
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(no details available) |
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Infrastructure - running costs: unchanged |
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(no details available) |
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Scale effects: not applicable |
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(no details available) |
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Amortisation: < 1 year |
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Good cost-benefit ratio: virtually no investment required. |
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Application outside railway sector (this technology is railway specific)
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Overall rating
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Overall potential: interesting |
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Time horizon: short-term |
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A more differentiated concept for the regulations limiting longitudinal forces in the train is an interesting measure to remove barriers to regenerative braking in some fields. However, the fleet-wide effect will be moderate. Nevertheless given the good cost-benefit ratio, the measure is worth considering. |
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date created: 2002-10-09
