BRUSSELS – The introduction of the European Union’s nascent real-driving emissions test, using onboard-vehicle portable-emissions-measurement-systems devices rather than laboratories to measure tailpipe output, is under threat.

The European Parliament’s influential environment, public health and food safety committee votes 40-9 to veto the proposed test, with 13 abstentions. But for the RDE to be blocked outright, that result must be backed by a majority of parliament’s 751 members, or by 376, when the full house votes on the issue in January.

If that happens, the European Commission, the EU executive, would be sent back to the drawing board to draw up a test and associated rules that could be authorized for use within the EU. It probably would mean the test would not be operational for assessing new-car models that are to be released by Sept. 1, 2017. The resolution passed by the committee demands that the Commission makes a replacement real-driving-emissions proposal by April 1, 2016.

Of particular concern to the lawmakers is the so-called conformity factor for nitrogen-oxide emissions, a tolerance which means vehicles could emit 110% over the EU’s current NOx limit of 80 (mg/km), going down to 50% more from September 2020 for new models and a year later for all new cars.

The EC says the tolerance is needed to account for technical uncertainties with the portable-emissions-measurement-systems devices, but lawmakers on the committee argue the EU executive itself recognizes (based on analysis from its Joint Research Centre) that the maximum margin of measurement error with PEMS is 30%, and the average 18.75%.

The EC, however, is sticking to its guns with a spokeswoman telling WardsAuto the test, which EU member states backed overwhelmingly in late October during a technical committee meeting of their representatives “will have a net effect on the amount of air pollution emitted by cars.

“Today’s divergence will be brought down from the current average of 400% to 110% from September 2017 and to 50% from January 2020. This is a significant reduction compared to the current discrepancy.”

The EC spokeswoman continues: “This is even more telling if put in terms of actual real emissions. We are moving from the current average real NOx emissions of 400 mg/km down to 168 mg/km (September 2017), then to 120 mg/km (January 2020). So we are more than halving the real amount of NOx emissions. And that is what matters to protect health and the environment.”

In addition, PEMS devices will be subject to annual review starting in 2020. “As this technology improves, we will be able to reduce the 50% error margin further,” the spokeswoman says.