This GTR prescribes a test cycle and test procedures to measure the emissions (including off-cycle) and fuel efficiency of light-duty vehicles. The GTR was adopted at the March 2014 session of the World Forum.

A supplemental “phase 1b” is underway to refine certain elements of the initial regulation. WP.29/AC.3 expects to consider a proposal for Amend. 1 to UN GTR No. 15 in November 2016 as result of Phase 1b activities.

A second phase is expected to address low ambient temperature, high altitude test procedures, and possibly durability and conformity issues.

A third phase would eventually include the addition of reference fuels, correlation across existing regional/national cycles, and introduction of emissions limits.

The latest draft version of the amended GTR is regularly updated by the WLTP informal working group.

The regulation is also supplemented by a gearshift calculation tool.