The Volkswagen diesel scandal has led to much greater scrutiny on the methods regulatory agencies use to test vehicle emissions, particularly in Europe.
Even before news of Volkswagen's diesel "defeat device" software broke, the European fuel-economy testing cycle was known to be overly optimistic, producing results that buyers could not replicate in real-world driving.
Now, the European Union is putting pressure on its members over lax national enforcement of emission-testing standards.
DON'T MISS: EU starts legal action against Germany, UK for failing to act on diesel emissions (Dec 2016)
Last Thursday, the European Commission issued guidance to members over how to ensure carmakers properly complied with emissions regulations.
The EU believes members are not adequately policing carmakers, and worries this may leave the door open for future emissions cheating, reports Reuters.
The new guidance is meant to clarify how each country's existing emissions-testing rules should be implemented, officials said.
Portable Emissions Measurement Systems (PEMS) on a Peugeot 308
The 11-page document issued by the European Commission is not legally binding, but the Commission may try to use it as the basis for legal action against member states it concludes aren't cracking down on potential cheating.
It includes a table of suspicious behaviors that may indicate the presence of "defeat device" software used to lower a vehicle's emissions during a test, but not in real-world use.
These include higher levels of emissions during hot engine starts than in cold starts.
ALSO SEE: EU fuel-economy ratings move further from reality; Mercedes tops offender list (Dec 2016)
Under current EU rules, automakers are allowed to use software that affects emissions, but only to protect engines from possible damage.
However, the new guidance states that automakers must prove to regulators that irreparable damage would result without the software.
The guidance also said that software related to lowering maintenance costs is unacceptable if it affects emissions.
2010 Volkswagen Golf TDI
The new guidance comes after the European Commission began legal action in December against seven EU members, including Germany and the U.K.
It accused those two nations, as well as Spain and Luxembourg, of not having adequate penalties to deter future emissions cheating.
Germany and the U.K. were also accused failing to disclose the details of suspicious findings by their own national investigations into cheating by carmakers.
MORE: Emission debate in Europe: should new EU agency test, or each nation? (Nov 2016)
The Czech Republic, Greece, and Lithuania were cited for not having provisions in their national regulations to fine automakers that violate emissions rules at all.
Germany—which the Commission suspects of pandering to its powerful auto industry—has said current regulations are too vague, and that an independent EU agency should be formed to ensure uniform enforcement.
Under current rules, individual nations are responsible for emissions certification, meaning countries can contradict each other on whether an automaker is cheating, Germany's transport minister has said.
[hat tip: John]