Background Interest for bicycling is increasing for transport, and also for health promotion. In cities with demanding traffic pattern, bicycling might be a dangerous activity. Due to lack of knowledge health and traffic authority financed an in-depth investigation of bicycle injuries treated in Oslo University Hospital (OUH), both as in and out patients. Continuous injury monitoring in the AED since 2003 gave possibility to follow trends.

Methods The study was a one-year prospective in-depth investigation with 20 variables. All patients contacting the AED due to a bicycle injury filled in a one-page form with description of 14 variables of the accident and a free text. Health personnel collected relevant information for patients arriving by ambulance and those not able to fill in form themselves. Based on previous studies it is estimated that about 85% of all injured persons from the Oslo population are treated at OUH.

Results 2184 persons were treated due a bicycle accident in 2014, 71% were single accidents. 65% were men. Median age was 34 years, for women 32 years. 20% were head injuries, 33% fractures, higher than average fracture rate in all injuries. 80 injuries were serious (AIS 3), 8 severe (AIS 4) and 3 critical (AIS 5). 60% of the injured had used helmet, and got fewer head injuries than those without helmets. 10% were influenced by alcohol/drugs. 77% (N = 1673) happened in “inner” city, 13% in wooden areas in the city, 7% in other municipalities, and 3% abroad. In 10% (N = 164) of injuries in “inner city”, tram rails were involved. Police registered 125 bicycle injuries in “inner city” during 2014, 7% of injuries treated at OUH. Since 2003, population of Oslo has increased by 22%, bicycle injuries by 21%.

Conclusions Incidence of bicycle injuries in the population of Oslo seems to be rather stable during the last 12 years. They are more severe than injuries in average. Patients without helmets have more head injuries than patients with helmets.