Cheating by manufacturers and tampering by owners leading to car pollution

Hans India

14-06-2025

Emission control systems in modern cars have slashed air pollutants such as particulate matter and nitrogen oxides. But these systems face two major challenges: carmakers cheating on pollution tests and owner tampering. Cheating means high-polluting cars can be sold when they shouldn't be, while tampering can increase some pollutants up to 100 times. In our new research review, we found the impacts of cheating and tampering on emissions of pollutants are substantial across the globe.
For instance, researchers in Spain found almost half the diesel trucks had been tampered with, while the Volkswagen Dieselgate cheating scandal uncovered in 2015 led to an estimated A$60 billion in health costs in the European Union.
The solutions? Better detection of tampering, cheating and malfunctioning emission systems – and vigilance to get high polluting cars off the road. How did we get here?
From the 1950s onwards, smog, air pollution and health issues from car exhausts led many regulators to require carmakers to reduce dangerous air pollutants. These days, modern combustion-engine cars are complex computer-controlled systems optimised to balance engine performance, durability and emission control. Authorities in many nations rely on testing to see if a new model is emitting at rates low enough to meet emission standards. Manufacturers can take advantage of the known quirks of official tests and intentionally alter how their vehicles operate during testing. To do this, they may install a 'defeat device', usually deep in the car's engine or its computer code. These devices shift the car to a special low-emissions mode if testing is detected. They're typically easy for the automaker to install and difficult to detect. Defeat devices are mainly found in diesel cars and trucks, since diesel emissions control systems are more complicated and expensive than petrol or LPG. Adding an emission control system to meet Euro 6 standards costs about $600 for a petrol car. For diesel, the cost can be three to five times higher.
In 2015, the United States Environmental Protection Agency and the state of California announced Volkswagen had been using a software-based defeat device to make its diesel cars appear substantially cleaner. The scandal drew worldwide attention and cost the company about $50 billion. For those caught, large fines and mandatory recalls have followed. But this hasn't been enough to stop the practice. The way these tests are conducted usually must be disclosed by law to ensure transparency and make results comparable and repeatable. Unfortunately, having detailed knowledge of the tests makes it easier to cheat. Tampering by car owners Tampering is largely done by owners of diesel cars and trucks. Owners can tamper with emission control systems to improve performance, rebel against laws they don't agree with or avoid extra costs such as Adblue, a liquid needed to reduce nitrogen oxides emissions from diesel trucks. Tampering is usually illegal. But that hasn't stopped the production of aftermarket tampering devices, such as software which deactivates emission control systems.
It's not necessarily illegal to sell these devices, but it is illegal to install and use them. In the road freight sector, the use of aftermarket tampering by vehicle owners also acts as an unfair economic advantage by undercutting responsible and law-abiding operators.
Combustion engine cars and trucks will be on the world's roads for decades to come. Ensuring they run as cleanly as possible over their lifetime will require independent and in-service emissions testing. Authorities will also need to focus on enforcement. Creating an internationally agreed test protocol for the detection of defeat devices will also be necessary.
Combating tampering by owners as well as malfunctioning emissions systems will require better detection efforts, either through on-road emissions testing or during a car service. One approach would be to add telemetry to the onboard diagnostics systems now common in modern cars. Telemetry radio transponders can report emissions problems to the owner and relevant authorities, who can then act.
Shifting to EVs offers the most robust and cost-effective way to combat fraud and cut exhaust pollutants and carbon emissions from road transport. But this will take decades. Authorities need to ensure diesel and petrol vehicles run as cleanly as possible until they can be retired.
(Robin Smit is associated with the University of Technology Sydney and Alberto Ayala is from West Virginia University)