Over 1,000 in-depth, On-The-Spot (OTS) crash investigations have been carried out in the UK since this project was first announced at the 17th ESV conference in Amsterdam. The UK government funds two teams whom routinely attend the scene of road crashes within 15 minutes of incidents occurring. This paper presents an overview of progress to date. The OTS methodology is described and crash examples presented that outline the vehicle, human and highway factors, which are all addressed by the study. This ambitious work is undertaken to allow research to be conducted that will investigate the causes of crashes, their subsequent injuries and the associated societal costs. It is recognised that only through a detailed knowledge of these complex casual factors will effective countermeasures be developed and ultimately successfully applied to improve road transport safety.