RS: Resistance factors for calculating train resistance

Request from Torben Brand:

According to the Wiki: "The sum of vehicle resistances is not the total of train resistance due to aerodynamic effects of vehicle formations. Therefore the resistance value is preferable given for the entire formation of the train. Dependent on the purpose there are different formulas used for the calculation of speed related values. RailML offers two basic possibilities of train resistance value representation - valueTable oder mathml."

As we have well established formulas in the sector I suggest to add the factors for the three most common resistance equations in/of the formation:

• Strahl / Sauthoff (Strahl for locomotives and freight wagons and Sauthoff for passenger wagons)

• Davies formula (mass dependent) [F=mg/1000(A+Bv+Cv^2]

• Davies formula (mass independent) [F=A+Bv+Cv^2]

I suggest extending the rolling stock schema with the following elements, this first in the Norwegian extension railML2.3NO: and if the community and RS coordinator agrees later in railML 2.4:

@strahlFactor [N]

@daviesMassFactorA [N] (mass dependent)

@daviesMassFactorB [N]

@daviesMassFactorC [N]

@daviesFactorA [kN] (mass independent)

@daviesFactorB [kN]

@daviesFactorC [kN]

I suggest to be more precise to define the attribute @resistanceFactor if it can be also be applied in the Strahl formula for locomotives in a formation.