Field studies under controlled circumstances have demonstrated adverse impacts of highways on breeding birds. These studies show that the presence and use of highways deteriorates habitat quality of a selected number of breeding birds from forests and wet meadow birds, resulting in lower population densities along roads. Studies showing effects on the national population level, however, are not available. The project aimed to describe impacts of highways on the population level for a wide variety of breeding birds in the Netherlands. During the last twenty years, SOVON - being a non-governmental organization - has built up enormous data on the distribution and numbers of Dutch breeding birds. Also plots were monitored yearly on the presence of breeding birds during a considerable period of time. The availability of these data addressed the question whether the increase in the Dutch highway length and traffic intensity that took place from 1975 to 2000, has lead to significant changes in the distribution of breeding birds. In contrast with other