20558: How does FBS calculate the relevant gradient for the minimum braking percentage?
The minimum braking percentage of a section of the route are calculated from the permissible speed, the pre-signal distance, the braking position and the so-called decisive gradient. FBS uses the effective slope of a connecting line, which is as long as the pre-signal distance of the line, but a maximum of 1000 m*. The use of the pre-signalling distance is intended to ensure that the braking distance of a train does not become longer than the pre-signal distance at any point in the route. This satisfies the obvious objective of DB Directive 457.0401.2 para. 2a, point 1. In addition, the braking distance should also be no longer than the pre-signalling distance, where there is no regular pre-signalling (where there is no pre-signal / cross board – main signal / trapeze board, supervision signal – crossing, braking distance before stops) a quasi-pre-signalling distance can be established on every point (for example due to a rail break)(EBO §35). The length limitation to 1000 m is based on R457.0401.2 paragraph 2a point 2.
For the pre-signalling distance, FBS uses the regularly pre-signal spacing, as entered in infrastrucutre data / classification, since the actual pre-signal spacing is not deposited in FBS. If the actual pre-signal spacing at the critical point is shorter than the regularly pre-signalling distance, it may therefore be that the minimum braking percentage calculated by FBS are too low. You must therefore check the FBS values in the driver's timetable in any case. It is also possible to enter the actual approach signal distance, if applicable only for the relevant (short) section part, under the data of the stretch / classification.
(* Background for Experts: The connection line is depicted as a homogenous tape with the length of the pre-signal distance of the line - maximum 1000 m - The mass volume "travels" the distance in deterministic small steps. Background for the usage of a longer connection line is the energy balance out of kinetic and potential energy over a distance corresponding approximately to the expected braking distance.)
Last update on 19.03.2020 by iRFP Support.