Overtaking is one of many important behaviour considered in the analysis of road traffic accidents and performance of single carriageway road. This paper seeks to determine factors affecting the speed of an overtaking vehicle. The study was conducted for a single carriageway road section which is flat and straight so that there is no effect of sight distance on overtaking. Overtaking behaviour data were recorded using a video camera. The data extracted from the video recordings were the decision times, overtaking times, overtaking distances, safety margins, accepted and rejected gaps, headways at the start of the overtaking manoeuvres, headways at the end of the overtaking manoeuvres, speed of the overtaken vehicle, speed of the overtaking vehicle at the end of the overtaking and acceleration of the overtaking vehicle during the overtaking. The data were analysed statistically to establish relationships between the various overtaking parameters. This study found that the speed of overtaking vehicle was affected by the speed of overtaken vehicle, drivers’ decision times, safety margin, overtaking times and acceleration.