Emissions from heavy-duty vehicles will be monitored as a first step toward curbing pollutants on course to reach unsustainable levels, the EU said Wednesday.

European Climate Action Commissioner Connie Hedegaard said heavy-duty vehicles are responsible for about a quarter of the carbon dioxide emissions from the European Union's transportation sector.

"Today we are taking the next steps to curb emissions from road transport," she said in a statement from Brussels. "This strategy outlines new measures which over time will cut CO2 emissions of these vehicles, save operators money and make the EU less dependent on imported oil."

Hedegaard said that, without action, emissions from heavy duty vehicles will reach exceedingly dangerous levels in the coming decades.

As a first step, she said the effort to reduce CO2 from trucks, buses and coaches would focus on certifications, reporting and monitoring of emissions. So far, she said, efforts to contain emissions have been difficult because of the large variety of models and sizes of heavy vehicles on European roads.

The EU in May said CO2 emissions for the 28 member states declined by 2.5 percent in 2013, compared with a drop of 1.6 percent the previous year.