Increased bicycle helmet use in the absence of mandatory bicycle helmet legislation: Prevalence and trends from longitudinal observational studies on the use of bicycle helmets among cyclists in Denmark 2004-2022

INTRODUCTION

Using a bicycle helmet reduces the risk of serious head injuries among cyclists substantially. This makes it highly relevant to increase the use of helmets and to measure the prevalence of bicycle helmet use over time and across different groups.

METHOD

Since 2004, the use of bicycle helmets in Denmark has been measured observationally in two nationwide time series: one among cyclists in city traffic across all age groups, and one among cycling school children (aged 6-16) around schools. The observations have been conducted on a regular basis in different parts of the country following the same methodology over the years.

RESULTS

Bicycle helmet use among cyclists in city traffic in Denmark has increased from 6% in 2004 to 50% in 2022. Among cycling school children, helmet use has increased from 33% in 2004 to 79% in 2022. Throughout the years, helmet wearing rates have been highest among young children and lowest among young adults. Since 2015, female cyclists in city traffic have had a slightly higher helmet use than male cyclists.

DISCUSSION

Several factors might have affected bicycle helmet use in Denmark. One possible factor is a nationwide focus on traffic safety education and behavior change campaigns to encourage helmet wearing. Furthermore, among stakeholders on cycling safety there has been consensus on recommending bicycle helmet use and supporting the promotion of helmets while not recommending or promoting helmet legislation. Finally, more safety-oriented behavior in road traffic in general, and self-reinforcing effects of increased helmet use have plausibly been important factors.

PRACTICAL APPLICATIONS

Increasing bicycle helmet use in a country where cycling is popular is possible in the absence of mandatory bicycle helmet legislation. Persistent behavior change campaigning and education, stakeholder consensus, higher levels of road safety-oriented behaviors, and self-reinforcing processes could potentially be important factors.

On the evaluation of visual nudges to promote safe cycling: Can we encourage lower speeds at intersections?

OBJECTIVE

Crashes between cars and cyclists at urban intersections are common, and their consequences are often severe. Typical causes for this type of crashes included the excessive speed of the cyclist as well as car drivers failing to see the cyclist. Measures that decrease the cyclists' speed may lead to safer car-cyclist interactions. This study aimed to investigate the extent to which cyclists may approach intersections at a lower speed when nudged to do so.

METHODS

Visual flat-stripe nudges were placed on bicycle lanes in the proximity of uncontrolled intersections (with a history of car-cyclist crashes) in two locations in Gothenburg, Sweden. This specific nudge was the one obtaining the best results from a previous study that tested different nudges in controlled experiments. Video data from the intersections were recorded with a site-based video recording system both before (baseline), and after (treatment), the nudge was installed. The video data was processed to extract trajectory and speed for cyclists. The baseline and treatment periods were equivalent in terms of day of the week, light, and weather conditions. Furthermore, two treatment periods were recorded to capture the effect of the nudge over time in one of the locations.

RESULTS

Leisure cyclists showed lower speeds in treatment than in baseline for both locations. Commuters were less affected by the nudge than leisure cyclists. This study shows that visual nudges to decrease cyclist speed at intersections are hard to evaluate in the wild because of the many confounders. We also found that the effect of visual nudges may be smaller than the effect of environmental factors such as wind and demographics, making their evaluation even harder.

CONCLUSIONS

The observed effect of speed might not be very high, but the advantage both in terms of cyclist acceptance and monetary cost makes an investment in the measure very low risk. This study informs policymakers and road authorities that want to promote countermeasures to intersection crashes and improve the safety of cyclists at urban intersections.

Measurement method for objective cyclist behavior parameters

Objective: The objective of this research is to study the feasibility of measuring behavioral indicators that reflect effects of infrastructure and interaction with other road users.Methods: An observation study was performed using 6 cameras above a separated cycle path next to a road which included a crossing with both cyclists and cars. A learning method based on Single Shot MultiBox Detector was applied to automatically detect the cyclists, and cyclist tracks were determined. Next, kinematic parameters were calculated from the cyclists' tracks. Amongst others, the cyclists' intensity, speed, position on the cycle path, and the distance to each other were analyzed for a busy period as well as for a quiet period of the day.Results: With the measurement method developed in this study it is possible to analyze the cyclists' intensity, the space they use at the cycle path, their average velocity, waiting times, the space and velocity amongst each other, and red light negation. However, collisions were not seen in the dataset analyzed, and the data is not sufficiently accurate to analyze sudden braking actions.Conclusion: It can be concluded that the developed measurement method provides insight of the cyclists' behavior in such a way that it can already be used for obtaining information to make changes to the infrastructure that will improve the comfort and safety of cyclists. The method could be further developed for doing qualitative comfort and safety analyses, and for doing analyses of the interaction between various types of road participants.

Aggravating and mitigating factors associated with cyclist injury severity in Denmark

INTRODUCTION

Denmark is one of the leading cycling nations, where cycling trips constitute a large share of the total trips, and cycling safety assumes a top priority position in the agenda of policy makers. The current study sheds light on the aggravating and mitigating factors associated with cyclist injury severity on Danish roads by examining a comprehensive set of accidents involving a cyclist and a collision partner between 2007 and 2011.

METHOD

This study estimates a generalized ordered logit model of the severity of cyclist injuries because of its ability to accommodate the ordered-response nature of severity while relaxing the proportional odds assumption.

RESULTS

Model estimates show that cyclist fragility (children under 10 years old and elderly cyclists over 60 years of age) and cyclist intoxication are aggravating individual factors, while helmet use is a mitigating factor. Speed limits above 70-80 km/h, slippery road surface, and location of the crash on road sections are aggravating infrastructure factors, while the availability of cycling paths and dense urban development are mitigating factors. Heavy vehicle involvement and conflicts between cyclists going straight or turning left and other vehicles going straight are aggravating vehicle involvement factors. Practical applications: The results are discussed in the context of applied policies, engineering, and traffic management solutions for bicycle safety in Denmark.