In the Netherlands, where parties awarding public transport concessions are free to include environmental requirements in their terms of tender, the North Brabant regional authority has drawn up a list of measures designed to promote greener public transport. At the authority’s request, CE Delft has taken a closer look at the cost and impact of some of these measures. The main focus was on measures to reduce emissions of nitrogen oxide (NOx) and particulates (PM10). The options examined related to accelerated introduction of newer and therefore cleaner diesel buses to the public transport fleet and to a (possibly phased) transition to natural gas as a vehicle fuel.