Every year, in Sweden, more than 4,000 people require inpatient care for single injury incidents obtained while walking or bicycling in a traffic environment. The aim of this study is to describe causes of single injury incidents among pedestrians and bicyclists and to identify preventive strategies. The study is based on data from the injury registration database at the University Hospital in Umeå and from a complementary questionnaire containing questions regarding the causes of injury and preventive strategies. The questionnaire was distributed to all pedestrians and bicyclists injured in single incidents in a city in northern Sweden and who had visited the hospital in 2009 because of those injuries. The data set is comprised of medical data for all 367 patients (244 pedestrian and 123 bicyclists) who responded to the questionnaire. The results from this study show that the pedestrians and bicyclists differ in their reports regarding causes of their injuries and the differences seem to be related to injury severity. The pedestrians mainly referred to environmental factors as causes to their injuries, while the bicyclists referred to environmental factors, product factors, and human factors as causes of the injury incident. Regarding preventive strategies, the views of the pedestrians and the bicyclists is in line with their views of causes to their injuries. The results are useful for developing preventive strategies for differing groups of road users.