Vehicles will get tested for real driving emissions in real traffic conditions from today onwards to ensure durable emissions performance and to prevent emissions cheating

Photo: Wikimedia Commons

India meets yet another milestone in the internal combustion engine (ICE) technology trajectory today. All cars, SUVs and goods vehicles with maximum weight not exceeding 3.5 tonnes to be sold from April 1, 2023 onwards, are to be tested for real driving emissions (RDE).

This is a critical step forward to check gaps between emissions performance during certification in laboratory and in the real world driving conditions. This is needed to make emissions control systems more effective, durable and prevent use of defeat devices or a software code in the vehicle that deactivates emissions control systems under certain operating conditions in the real world.

The RDE regulations simply mean that vehicles will also get tested in real traffic conditions based on speed, acceleration, and braking as per our real-world usage patterns. Also, after vehicles are sold, a random sample will be picked up from the market for testing in real world driving conditions to establish compliance with norms when in service.

This is a dramatic departure from the conventional practice of testing vehicles only in laboratories where a driving pattern or test cycle is simulated under controlled laboratory conditions. That cannot capture the full range of emissions from vehicles when driven on the roads.

Making of RDE regulations

The Union Ministry of Road Transport and Highways (MoRTH)  had set up a committee in December 2016 to develop the RDE regulations and it was steered by the International Centre for Automotive Technology (ICAT).

The RDE regulations were included in the original Bharat State 6 emissions standards (BS6) in 2020. But industry and vehicle certification agencies were given three years to generate and collect data to decide some critical parameters for testing and enforcement. All the RDE rules have been detailed out in Automotive Indian Standard (AIS) 137 (chapter 20).

Subsequently, the MoRTH issued a notification on February 17, 2023 that makes RDE enforceable from April 1, 2023 onwards. RDE is a much tougher testing system. The real world emissions are usually influenced by highly variable factors that cannot be controlled.

These include ambient temperature, pressure, humidity, road conditions, altitude, fuel composition, engine technology among others. Within these boundary conditions, the overall emissions cannot exceed a specified limit on road. This makes the system even stronger and ensures durable emissions performance.

To develop these regulations, ICAT has tested vehicles in different parts of the country covering more than 10,000 km to generate data. For this purpose test routes were also identified in selected cities to include urban, rural and highway stretches for representative driving conditions.

Industry proves it can do better

RDE is a big leap from the early years when there was a lot of hesitation among the industry players about the adoption of real world driving emissions testing as part of the BS6 regulations.

There was uncertainty about the conformity factor (CF) or the margin that is allowed between the tested norms in the laboratory and the real world emissions results.

The extra margin is considered to account for the measurement uncertainties in the testing with portable emission measurement equipment (PEMS). This factor is simply a multiplier of the emissions standards. But this should not be too lax.

It is encouraging that the conformity factor of 1.5 (1.5 CF) that has been finally adopted for testing of all gaseous pollutants and  particle number has been notified by the MoRTH on February 17, 2023. This also aligns with Europe.

This is certainly an improvement over a more lenient margin of 2.1 that was originally considered.  It may be recalled that the  AIS 137 Part 3 draft had originally provided for — a “presumption of confirmatory with requirement of 2.1 — to be assessed by additional RDE test.” 2.1 is a more relaxed margin for RDE compliance.

This improvement has been possible because the analysis of test data showed that the Indian industry has done batter already.

It is evident from the ICAT’s assessment of the test data that as many as 93 per cent of the generated data for nitrogen oxides (NOx) was at a level less than 1.43 CF and 99.61 per cent for particle number was less than 1.5 CF. This on-ground assessment has helped to tighten the original presumption. 

However, it may be noted that Europe is moving quickly towards tighter CF to reduce the margin further to as low as 1.32 CF and 1.23 CF.

Overall, the Indian regulations have aligned with the package 3 of RDE regulations of Europe adopted around 2018. However, some parameters have been modified to suit the Indian conditions.

These include lowering the speed range for urban, rural and highway driving compared to the European range. Also the temperature range has been taken on a higher side compared to Europe.

What RDE means for vehicles

Compliance with new RDE regulations will require much more effective, complex and durable emission control systems particularly for NOx and particle numbers in diesel vehicles.

Complex systems like selective catalytic reducing systems and lean NOX traps for NOx control and particulate filters in diesel vehicles will be more expensive and more difficult to maintain. Their usage may also result in some fuel penalty that may have to be addressed.

Also while RDE regulations are getting enforced, simultaneously tighter fuel economy norms and onboard diagnostic stage II norms are also kicking in. Overall the costs are expected to increase especially for the diesel vehicles.

Already, the media is abuzz on how diesel cars especially smaller and mid segments are threatened and several popular models will exit. As reported in media, these include Hyundai’s i20 Diesel, Skoda’s Octavia, Superb, Maruti Suzuki’s Alto 800, Honda’s City 5th Gen Diesel, Amaze Diesel, Jazz etc, Mahindra: Marazzo, Alturas G4, KUV100, Tata’ Altroz Diesel, Renault’s Kwid 800, Toyota Innova Crysta Petrol among others. SUVs are comparatively less affected than the smaller diesel cars.

RDE needed to avert diesel gate

Not a very long time ago, the diesel gate scandal involving several manufacturers across the US and Europe had shaken the world.

Following this, a spate of reforms including successive 4 packages including RDE regulations were implemented in Europe.

These regulatory reforms had even helped to lower the gap between the certification tests and real world emissions performance in several models.

But recently the US based non-profit International Council on Clean Transportation (ICCT) has released its findings from the review of the existing vehicle testing results from various sources including remote sensing measurements in Europe. 

They have found NOx emission levels too high indicating possible use of defeat devices. They have identified vehicle models that are above the identified threshold and have asked for further investigation of these vehicle models.

ICCT has found that about 85 per cent for Euro 5 and 77 per cent for Euro 6 diesel cars have “suspicious” excess NOx emissions while many show “extreme” emission levels — as per the threshold defined in the study. “Extreme” emission levels were found in at least 40 per cent of official tests of diesel cars, indicating “the presence of a calibration strategy that may now be considered a prohibited defeat device”, states ICCT.

This is a learning curve for India. 

Real world emissions matters: need to get better

The BS6 version 2 — including RDE and in-use compliance requirements that are rolling out today, set the stage for more stringent scrutiny of real driving emissions for durable real world emissions performance. 

RDE regulations will only get tighter now with further reforms in the anvil including adoption of a more improved testing cycle for certification — Worldwide Harmonized Light Vehicles Test Procedure (WLTP) that is closer to real world driving patterns. RDE testing linked with WLTP will be a stronger measure.

Moreover, India has already started to frame the  BS 7 mass emissions standards that will not only be more stringent, fully fuel neutral, but will also regulate greenhouse gases. Europe is expected to implement Euro 7 in 2025.

Clearly, the ICE trajectory is poised for a transformation that needs to be taken forward to bridge the gap with the global good practice. Regulation of real world emissions performance can maximise air quality and public health benefits. 

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