Professor Deniz Karman’s article “Shifting primary energy source and NOx emission location with plug-in-hybrid vehicles” was published last year in the Environmental Research Letters (ERL) and now has been selected by the editors of ERL for inclusion in the exclusive ‘Highlights of 2011’ collection. Papers are chosen on the basis of referee endorsement, novelty, scientific impact and broadness of appeal to collectively showcase the quality and diversity of ERL’s broad coverage last year. The full list of selected article highlights, including the best letters, perspectives and focus issues can be found here.