Working Paper

Focus on inertia classes

For historic reasons we make use of inertia classes and upper limits for inertia mass during the vehicle testing procedures today. Historically, the weight of a vehicle was represented by hanging rotating inertia mass on a dynamometer. This approach required the use of discrete inertia classes and an upper limit for inertia mass. Modern electronic dynamometers no longer impose these limitations. As a result it is now possible to revise existing test procedures and provide more accurate emission and fuel consumption values to consumers.

This document builds on explanations that were given in the documents WLTP-DTP-LabProcICE-054, 067, 077 and WLTP-DTP-06-11.1 It presents new analysis on the implications of the current inertia class based system and outlines two alternative approaches for discussion within the WLTP-DTP working group.

This paper was submitted to the UNECE GRPE informal subgroup on the development of a worldwide harmonized light vehicles test procedure (WLTP-DTP).