RAILSIM supports user-specified or default rolling resistance coefficients, including tunnel operation coefficients. The following algorithms for computation of rolling and aerodynamic resistance are available individually:

Davis (Basic)
The Basic Davis Equation is appropriate for high power/ton transit and commuter rail vehicles. This equation results in higher resistances than the Modified, Adjusted and Totten Revision versions of the Davis Equation. The coefficients for operations through tube (bored) tunnels and box structure tunnels originated with the Toronto Transit Commission.

Davis (Modified)
This equation results in resistances which are very similar to the AAR Equation and lower than the Basic Davis Equation. It is appropriate for freight trains with relatively high weights (gross car weights of 70 tons or more). Support for separate, user-defined tube (bored) tunnel and box structure tunnel operations is included.

Davis (Adjusted)
This equation includes freight car-specific adjustment factors to the rolling resistances calculated for individual freight cars, which are included for all entries in the RAILSIM rolling stock libraries. Adjustments increase rolling resistance for intermodal freight cars by 20 to 30 percent over other versions of the Davis Equation. The Adjusted Davis formula is appropriate for intermodal trains, particularly those with double-stack containers or mixtures of different intermodal car types (TOFC, single stack COFC, double stack COFC).

Davis (Totten Revision)
This equation results in calculated rolling resistances which are generally higher than the AAR and Modified Davis Equations, but lower than the Basic Davis Equation.

Association of American Railroads (AAR)
This equation takes the same form as the Davis Equation, but results in lower calculated resistances in most cases. It is appropriate for modern North American freight trains (typical gross car weights of 70 tons or more) but not for high power/ton ratio transit and railroad multiple units vehicles. For consistency with the Basic and Modified Davis Equations, coefficients for tube and box tunnel aerodynamic resistance can be user-specified. However, the AAR does not provide recommended coefficients for tunnel modeling and the default values are the same as for open air operation.

Canadian National
This equation was developed based on field testing of both freight and passenger railroad rolling stock. It takes the form of the Davis Equation, and includes coefficients for tube (bored) and box tunnel aerodynamic resistance.

TGV Network (SNCF)
This equation has been calibrated by the French National Railways for its high speed trains, including the TGV Paris-Southeast (PSE), TGV Atlantique, TGV Reseau and Eurostar trains. It is applicable to other high speed trainsets with a high degree of aerodynamic styling, but not to other types of trains. Its calculated rolling resistance is approximately 20 percent less at 100 km/h than the German Passenger equation, which DBAG (German National Railroad) uses for its high-speed ICE trains.

SNCF Electric Vehicles
This equation applies to high power/ton ratio electric vehicles, including rapid transit, commuter rail multiple unit and locomotive-hauled trains. Along with the RATP derivation of this equation, it is the only resistance methodology with a rail gauge input and a number of pantographs input. The SNCF formula includes a provision for increased aerodynamic resistance for operations in a tunnel. The formula is applicable to TGV (high-speed) trains as well, although the TGV Network equation has been more precisely calibrated for high speed trains.

Passenger Broad Gauge
This equation was developed by Mannheim and applies to 1.676 meter (broad) gauge rail operations only.

Mixed Freight Broad Gauge
This equation was also developed by Mannheim and applies to freight trains with a mixture of car types operating on 1.676 meter (broad) gauge railroads.

Passenger Narrow Gauge
This equation applies only to passenger trains operating on meter (narrow) gauge railroads.

Mixed Freight Narrow Gauge
This equation applies only to freight trains with a mixture of car types operating on meter (narrow) gauge railroads.