FERSI published a technical paper that sets out a scientifically valid method for assessing the prevalence of mobile phone use of car drivers, cyclists and pedestrians through on-road observations and self-reports. Mobile phone use is an important key performance indicator (KPI) for road safety. Mobile phones are a major source of distraction and contribute to the occurrence of accidents. Unfortunately, most countries do not yet have a reliable picture of the size of the problem and the developments over time. FERSI considers the current guidelines as an excellent basis for collecting scientifically reliable information about this highly relevant road safety issue.