The Volkswagen emissions scandal has rocked the automotive industry, and it was discovered accidentally as a result a routine test carried out by two engineers with The International Council on Clean Transportation (ICCT).
John German is a Senior Fellow with ICCT and he was one of those engineers, he joined Shane Coleman on Newstalk Lunchtime to discuss the discovery.
Initially his team wanted to compare VW diesel models being sold in the US and Europe - as it appeared that the models being sold there were more environmentally friendly.
When the tests on the cars from the US showed five to 30 times the emission levels that they had expected they contacted the California Air Resources Board (CARB) as they suspected that something was "seriously wrong."
He had to wait months for confirmation that the company had been cheating in these tests with defeat devices which detect when cars were being tested, and alter their performance to deliver favourable test results.
"I knew there was a real possibility that it could be a defeat device. I've been in the industry for 39 years - and I've been in emissions the whole time. But I never said that to anybody - that's not something that you say without proof."
Mr German found out the same way as everyone else that VW had been rigging tests - through media reports last Friday.
He was surprised by the scale of the scandal: "We did not expect the reaction that happened. This has been a much, much bigger deal around the world than we thought it would be."
The European Commission has called for individual states to begin their own investigations to see if European tests have also been rigged.
The next question is whether this practise is limited to VW - or if other car manufacturers are doing the same thing.
While he will not speculate as to whether this practise is widespread - Mr German says that he hopes that the industry as a whole will be properly scrutinised:
"We have no information, no data that suggests that other manufacturers also have defeat devices - but it's absolutely the right question to ask."
"Governments around the world need to do some real-world testing on other manufacturers in other countries - just to make sure that this isn't happening elsewhere," he adds.
Ireland's Road Safety Authority (RSA) is still considering whether an investigation will be launched here.
A statement from the body reads: “The RSA notes the recent disclosure by Volkswagen in relation to its testing of vehicle emissions to the appropriate American standards.
"It is our understanding that the European Commission is determining whether the European Emission Standard Testing has been affected by Volkswagen's announcement and the RSA is being kept abreast of same."
Up to 80,000 cars could be affected in Ireland.
