10250: Why is there a number of rounding rules in FBS, and why are they set differently for different timetables?
Traditionally, a distinction is made between "public" and "internal" timetable documents, and traditionally, different rounding rules apply for both types. In Germany this was typically the rule "round down" for in-house and "traffic rounding rules" for timetables to be published.
The traffic rounding rules always round "on the safe side": departure times are rounded down and arrival times are rounded up. In case of doubt, the journey time becomes longer and the time of the stay shorter. If you were to round down the arrival time (instead of rounding it up) from the travellers point of view, it would always look like there was a delay, and a possible transition would seem a minute longer than the transition time actually is - that would not be "on the safe side".
(As an exception to this rule, arrival times are rounded down and not rounded up, if, in the case of stays shorter than one minute, the departure time would appear to be earlier than the arrival time, and a seemingly negative time of residence would arise.)
Public timetable documents for which this rule is applicable are typically the customer's timetable (course book) and the arrival and departure posters.
For the rest of the company's internal timetable documents, such as the graphic timetable, the driver's working timetable, the circulation plan etc., it was customary to round mathematically or to round down everything. Possible reasons are that railroaders want to be "more honest" among themselves or that the traffic rule with the exception mentioned above is simply too complicated - we do not know the reason for this different approach. It is probable that the traffic rule was introduced in retrospect, potentially after negative experiences with alleged delays, but was not extended further than absolutely necessary.
Today, it is common practice in Germany to use the rounding rule "round down everything" for all timetable documents. A discrepancy between the various timetable documents due to different rounding rules is more likely to be a mistake, possibly also due to the increasing number of "outsiders" in the domain of timetable technology.
As a user of FBS, you can and must decide for yourself which rounding rule you want to use for which timetable documents. In the first timetable of every type, the traditional rules are set by FBS (the traffic rule for customer's timetable and arrival and departure posters and round mathematically or round down everything for the other timetable documents). In the case of further timetables, the rounding rule is taken over from the previous timetable of the same type so that the presetting does not have to be changed several times.
Before printing a graphic timetable, you can still change the rounding rule that is valid only for this print. This takes into account the frequent demand that one typically edits the graphic timetable with a 1/10-minute display, but wants to output it rounded to whole minutes.
In order to obtain uniform minute indications in all timetable documents, as an alternative to the above-mentioned, uniform application of round down everything it can also be considered to use the, with regards to content, "better" traffic rule or the mathematical rounds uniformly. For strategic (long-term) projects - especially with interval graphics - it is therefore also customary and recommended by us to round all times mathematically. Here the aspect of the apparent delays is minor in in comparison to a general "inaccuracy" of long-term calculated travel times.
Note: The occasionally visible internal accuracy of the FBS travel time calculations of 1/1000 minutes is not affected by the set rounding rule, but is used only to reduce a rounding error. The internal accuracy is therefore always rounded to 1/10 minutes, commercially. The rounding rule set by the user only concerns the question of how to round from 1/10 minutes to whole or half minutes.
Last update on 19.03.2020 by iRFP Support.