From bicycle crashes to measures: knowledge and knowledge gaps; Inventory for the benefit of the National Research Agenda Bicycle Safety (NOaF) Road safety of cyclists shows a less favourable development than that of other road users. As bicycle use will be stimulated in years to come and because the number of elderly cyclists will increase, it is important to improve bicycle safety. To achieve this, the Netherlands has drawn up the National Research Agenda Bicycle Safety (NOaF). The present study maps the existing knowledge about the development of unsafe cycling conditions and its backgrounds; on the one hand to use scientific knowledge as a contribution to a goal-oriented approach and on the other to identify areas in which the necessary scientific knowledge is still lacking. In addition to a comprehensive summary in the first chapter, this study comprises three parts. Part I gives insight in the magnitude, nature and development of unsafe cycling conditions in the Netherlands during the last two decades. Part II discusses the knowledge from international scientific research to acquire an insight in the causes of these crashes. Three lines of approach are distinguished: the cyclist and the other road users, the bicycle, and the infrastructure. Part III makes an inventory of the effects of the measures that have already been taken, and then looks ahead at the threats and opportunities that bicycle safety may face. The study concludes that compared with the extensive knowledge about the safety of motorized traffic, bicycle safety is mainly ‘terra incognita’. Keeping in mind social urgency, the size of the problem, the state of affairs concerning knowledge, and the technical research possibilities, the following ten research topics were selected, without giving priority. 1. Seriously injured cyclists in crashes not involving motor vehicles This type of casualties shows a strong increase in number, whereas the existing registries have no background information available about these crashes. Therefore, it needs to be determined how data on the characteristics of these crashes can reliably be gathered. 2. The development of Safety Performance Indicators for bicycle safety Safety Performance Indicators (SPIs) are characteristics of the traffic system that can determine its safety. They are necessary to identify the weaknesses in the system and to strengthen them before crashes occur. So far, bicycle safety has rarely been approached from the SPI angle because no SPIs have yet been set for bicycles. Examples could be ‘the required width of the cycle path in relation to the traffic volume’, or ‘safe speeds’ in conflicts involving bicycles and motor vehicles. Research focusing on the development of SPIs for bicycle safety is therefore required. 3. Injury protection for cyclists The large vulnerability of cyclists makes it necessary to determine what degree of protection is offered by helmets and external airbags, and how ‘injury inflicting objects’ such as kerbs, bollards and road signs can be screened off or be given a better design. 4. Expectations, predictability and behavioural routines in relation with bicycle safety The effects need to be determined of developments that are in conflict with the important principles described above. Examples are two-way cycle paths, noiseless motor vehicles, and intelligent vehicles that do not behave in a familiar way. 5. Hazard perception This higher order skill develops slowly. It needs to be investigated how well this skill is developed among cycling youths and, consequently, whether training will contribute to its improvement. 6. Elderly Considering the substantial rise in the ageing population necessitates the exploration of the possibilities to improve cycle safety for this age group. In that context, the question is relevant what the safety effects of e-bikes are for the older cyclists. 7. Evaluation of measures In order to make policy, 'evidence-based' measures for cycling need to be evaluated, thereby differentiating between effects on the safety of motor vehicles and on that of cyclists and other road users. 8. Development of research instruments Knowledge development and hypothesis testing studies of bicycle safety need to brought to a higher plane by developing valid and reliable research instruments. 9. Adaptation of international findings Not only in the Netherlands, but also in other countries, research is carried out into the safety of cyclists. In order to apply this knowledge in the Netherlands more insight is required into the ‘transferability’ of the findings from these international studies. 10. Connections and added value: 1 + 1 = 3 Much of the knowledge and research into the safety of cyclists also applies to pedestrian safety and many provisions that benefit the elderly may also increase the safety of the younger age groups. Furthermore, the research topics 3, 4, 5, 7, and 8 can also be extended to pedestrian safety. Making the most of these connections generates knowledge that can be applied more widely.