Northern Ireland must halve the volume of emissions from road traffic by 2025 if it is to meet climate change targets, according to official predictions.
A report from the Department for Regional Development (DRD) warned that further increases would significantly undermine the Executives ability to meet its overall aims.
Since 1990, there had been a significant increase in pollutants from transport, affecting progress in other areas, the report added.
There had also been a notable rise in rural driving and transport for construction materials, it stated.
The DRD review said: "While, it may be possible to pursue more ambitious reductions in other sectors to address potential shortfalls in transport, the fact remains that further increases in road transport emissions will significantly undermine the potential to successfully realise the Executive's targets and commitments in this area.
"Transport must therefore play its part. Indeed the outworking of the Climate Change Act, the Renewable Energy Directive and related legislation are likely to require action to reduce emissions from road transport."
A rapidly growing population and economic growth following the end of the conflict contributed to past increases in demand for transport, the dossier added.
Within freight transport there has been a particular rise in light goods vehicle traffic.Total greenhouse gas emissions from road transport increased by 53% between 1990 and 2006.
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