Factors affecting road mortality and the suitability of road verges for butterflies

► Roadkilled and living butterflies were counted on 60 transects at roads in Poland. ► At least 6.8% of butterflies on road verges died due to collisions with cars. ► Road mortality increased with a traffic volume, road width and verge mowing. ► Large verge width and high plant species richness decrease road mortality. ► Small species were most susceptible to collision with cars.