Technical considerations for implementing a Real Driving Emissions test for passenger vehicles in India

Published: 2018.05.31

Francisco Posada, Yoann Bernard, Liuhanzi Yang, Anup Bandivadekar

This position brief makes specific recommendations regarding the adoption of Real Driving Emissions (RDE) testing in India. The recommendations are geared towards ensuring that implementation of an Indian RDE program would narrow the gap between laboratory and on-road emissions performance of vehicles that should meet Bharat Stage (BS) VI emissions standards. An Indian RDE program should adopt aspects of the EU and Chinese RDE programs, while adjusting boundary conditions to better reflect Indian driving conditions.

We suggest the following changes to the AIS 137 proposal for the RDE testing program adoption in India:

Speed definitions for urban, rural and motorway operation: We recommend reducing the speed range definitions to better reflect Indian driving conditions for RDE testing. Defining three sections with two cut points set at 30 km/h and 50 km/h, with urban driving defined as under 30 km/h and motorway driving defined as over 50 km/h, results in time and distance distributions similar to those already in place for the European RDE testing, while keeping the distance-specific emissions within the expected emissions behavior of diesel technology.

Dissemination of RDE test results: Access to RDE test results as currently proposed will be available to only those involved in testing and approval procedures who have access to the unique identification number of a PEMS testing family. We recommend that starting April 2020, the Ministry of Road Transport and Highways (should directly, or though one of the designated testing agencies, compile and publish the RDE results with unrestricted public access. The only data requirements needed to access the RDE test information should be manufacturer, model year, model name and variant.

Trip Evaluation: We recommend the adoption of the Total NOX emissions evaluation as presented in the EU RDE 4th regulatory package. This method provides closer results to real-driving raw emissions, while ensuring urban driving emissions are properly evaluated during testing and addressed by manufacturers.

Conformity Factor: We recommend that India adopt a conformity factor (CF) timeline that starts RDE implementation with CF= 1.43 for NOX and PN emissions in April 2023 and moves to CF= 1.0 by April 2026. Multiple manufacturers and technology suppliers are already publicly showcasing application of after-treatment systems capable of meeting conformity factor of 1 on the road.

Validity of RDE Test: With the introduction of the fourth RDE regulation in EU, the moving average window (MAW) method will become the only method for determining the validity of a RDE test. The power binning method was never fully adopted for regulatory purposes. Thus, we recommend moving directly to the MAW method and dropping the power binning method and all references to it.

In-Service Conformity regulation: We recommend adopting PEMS-based tests as part of the In-Service Conformity (ISC) regulation for passenger vehicles in India and placing the testing responsibility with the type-approval authority. Manufacturer data would still be required but only as a way to screen for potential ISC tests subjects.