The new rule will require diesel vehicles sold in the EU to undergo tests on roads rather than in laboratories starting in September 2017.
The laboratory tests have drawn criticism from environmental groups as under-stating the real level of potentially harmful emissions from diesel cars.
Industry group ACEA said the new tests will require automakers to make major changes in testing and developing new vehicles but this will be difficult because the regulation is incomplete.
“The industry is being asked to design today for requirements that will only be known next year,” an ACEA spokeswoman said. The changes can only be made once there is full clarity on the new test cycle, ACEA said in a statement.
The lobby group said the current proposal is incomplete because it does not meet the following criteria: a comprehensive set of requirements; specified performance limits; dates of application for the regulation because the September 2017 start date is not yet confirmed by EU law.
ACEA is asking EU regulators for a “complete proposal” by June or July at the latest.
Diesel-powered vehicles are popular in Europe, accounting for half of new-car sales, because fuel is expensive and diesel engines are 15 percent to 20 percent more efficient than gasoline models. The better fuel economy helps to cut emissions of CO2, which is linked to climate change, but diesels emit higher levels of nitrogen oxides (NOx) and particulate matter that have been linked to asthma, cancer, lung disease and respiratory illnesses.
Politicians in countries such as France and the UK are considering regulation to ban or limit diesel cars in smog-hit cities including Paris and London. Paris aims to phase out diesel vehicles in the city by about 2020.
The environmental lobby group, Transport & Environment, said the new test rules will help to bring an end to “dirty diesels.” The next step will be for the European Commission and member states to agree on what the limits for the real world tests will be and from when they will apply, it said.
“The continuation of the current weak and ineffective testing regime has seen air pollution worsen with widespread health consequences and the prospect of cities banning diesel vehicles as the only remaining solution,” the group said in a statement.
A study by the ICCT group showed that the gap in 2013 between real world emissions were 33 percent higher than the official laboratory test results.
While the switchover to the new tests was expected, it nonetheless deals carmakers a hard blow because it means they face a heavy burden to meet tough CO2 targets after 2021 as well as the costs of moving to a new diesel test cycle.
Exane BNP Paribas said in a recent report: “We believe that the game is over for diesel.”
The equity researchers said if the new test cycle resulted in emission level figures of 10 percent above those of the current test, it could add development costs of up to 400 euros per car. Mass-market automakers, which typically make only 500 euros per car in a good year, would be hit badly, the report said.
The EU’s latest Euro 6 emissions standards mandate a reduction in NOx to 80 milligrams per kilometer for new cars sold from September of this year, down from 180mg/kg.