Question

In the context of the Road Load Matrix Family, how are aerodynamic drag and mass variances accounted for when defining the range of energy consumption for a vehicle group?

Accepted Answer

A Road Load Matrix Family is a grouping of vehicles that share identical aerodynamic and mass characteristics, allowing manufacturers to use a single set of road load coefficients for multiple vehicle configurations. Aerodynamic drag is accounted for by the frontal area and the aerodynamic drag coefficient, which together form the product known as the drag area. When defining the range of energy consumption, the vehicle with the highest drag area within the family dictates the worst-case aerodynamic resistance. Mass variance is accounted for by assigning the vehicle group a specific test mass, which represents the inertia of the vehicle during road load determination. The energy consumption range is established by testing the vehicle with the highest possible road load, which is determined by the combination of the highest drag area and the highest test mass permitted within that specific family. These coefficients are calculated using a formula that accounts for rolling resistance, air density, and the vehicle speed to ensure that the energy consumption values remain representative of all vehicles included in the matrix. By using these bounding values, the certification process ensures that every vehicle in the group is covered by the energy consumption range defined by the most demanding configuration.

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In the context of the Road Load Matrix Family, how are aerodynamic drag and mass variances accounted for when defining the range of energy consumption for a vehicle group?