To ensure that the cycling network remains safe after an increase in cycling, a well-developed, safe cycling network is needed. Studies investigating safe cycling often focus on design choices at road level, whereas route and network levels are also relevant. This study deals with cycling safety at route level. Firstly, it aims to define indicators to compare the safety levels of different routes between each origin-destination (OD) pair. Secondly, it aims to discuss how these indicators can be applied by road authorities in order to assess and improve the safety of cycling routes. Finally, it also aims to discuss the function of different types of infrastructure in the cycling network, as elements in cycling routes. The study focuses on cyclist routes within urban areas (built-up areas).
Safe route indicators
Indicators were developed to compare the safety levels of different cycling routes. Safe route indicators that hadve been developed for cars in a previous study were used and adapted to cyclists based on a literature review and the application of the functional requirements and principles of Sustainable Safety to bicycle traffic. This results in the following indicators:
- Travel distance as short as possible;
- Travel time as short as possible;
- Low intersection density, especially concerning intersections with distributor roads;
- Wherever possible, cyclists should follow exclusive bicycle tracks;
- Wherever possible, the use of 50km/h distributor roads without separate bicycle tracks should be avoided;
- As few left-turns as possible;
- As few transitions and discontinuities as possible.
These seven indicators aim to limit the exposure to potential risks and protect cyclists from motor vehicles. An additional eighth indicator, which is up for discussion, aims to protect vulnerable road users (pedestrians and vulnerable cyclists) from large volumes of fast-flowing bicycle through- traffic and other potential users of bicycle facilities:
8. Wherever possible, fast flowing and possibly heavy (high-weight) bicycle through-traffic should be separated from ‘residents’ and vulnerable bicycle traffic.
Although this eighth indicator is in line with suggestions from Fietsberaad and the Dutch Cyclists’ union, there is no evidence for the necessity of this additional indicator. Apart from the lack of evidence, there are some complications in operationalising and implementing the proposed indicator.
Improving safety levels of cycling routes
In order to improve the safety of cycling routes, road authorities can take measures at network level and at local level. Network-level measures include changing the network structure or functional role of links in the network. Measures at local level focus on the design of individual elements (road sections, intersections, transitions) in the network.
The eight indicators discussed above can be applied to identify locations in the network where cyclists’ route safety can be improved. The first step is to carry out a network analysis in order to identify important cycling routes based on the existing travel demands and the network structure. The second step is to score the identified routes using the first seven route indicators discussed above. The scores can be visualised using a so-called route star. As a third step, different options can be identified to improve cyclist safety at route level. In general, there are three options: 1) existing routes can be made safer, 2) alternative safer routes can be created, or 3) safe routes can be made more attractive to cyclists. Moreover, a distinction can be made between measures at network level and measures at local level. The table below provides an overview of potential measures.
Network-level measures:
- Separate motor vehicle flow traffic from access roads and bicycle traffic
- Create direct cycling routes with minimal detour
- Create exclusive bicycle tracks where possible
- Create bicycle through-routes on exclusive bicycle tracks
- Low motorised and bicycle traffic speeds on roads with strong exchange function
- Introduce grade separation or avoid cycle route intersections with distributor roads
- Avoid left turns and transitions between infrastructure types which require cyclists to cross with motorised traffic
- Make safe routes more attractive to cyclists, for example by increasing comfort or adapting traffic light settings
Road-level measures:
- Create separated bicycle tracks along distributor roads
- Limit speeds where conflicts between cyclists and motor vehicles can occur
- No obstacles in the cycling infrastructure
- Sufficiently wide bicycle tracks
- Quality surface: smooth, complete, clean, not slippery
- Visual guidance
- Forgiving track edges and verges
Function of different cycling facilities
The table below proposes the different types of cycling facilities and their primary function in the cycling network. Exclusive bicycle tracks are preferred for serving large volumes of (relatively high- speed) ‘through’ cyclists. Access roads, depending on their characteristics, can either be adapted to serve (larger volumes of relatively high-speed) through-traffic or mainly serve local bicycle traffic. Bicycle streets, while requiring further research into their safety and ideal characteristics, may be an option to serve flow cyclists on access roads when exclusive bicycle tracks are not feasible. Distributor roads are primarily intended for motorised through-traffic and can potentially serve a function for bicycle through-traffic as well. However, due to the high motorised traffic speeds it is important that physically separated bicycle tracks are present and intersections are minimised and as safe as possible.
Exclusive bicycle tracks - Cyclists 'Flow'
- Wide enough to support variety of bicycle types and speeds
- High bicycle traffic volume
- Low adjacent pedestrian volumes
- Few intersections, side-roads
- Safe track-side verges
- Bidirectional bicycle traffic
Access roads: flow - Cyclists 'Flow', motor vehicles 'Exchange'
- Potential bicycle streets
- Low motorised traffic speeds
- Low motorised traffic volumes
- Minimal exchange traffic
- Few intersections, side roads
Access roads: exchange - Cyclists 'Exchange', motor vehicles 'Exchange'
- Traffic calming
- Lower cycling speeds to protect vulnerable cyclists and pedestrians
- Low motorised traffic speeds
- Low motorised traffic volumes
Distributor roads - Cyclists 'Flow', motor vehicles 'Flow'
- Separate bicycle track
- Uni- or bidirectional bicycle traffic
- Avoid at-grade intersections
Recommendations for further research
A few areas have been identified for further research. First, while the first seven indicators have each been shown to have a relation with bicycle safety, the combination of this particular set of indicators into a total route safety score has not been validated and weight factors have not been determined yet.
Second, there is no scientific evidence yet for the eighth indicator. Further research related to this indicator could for example focus on causes and nature of bicycle crashes without motor vehicles. Regarding the feasibility of this indicator, future research may also investigate the relation between variation in cycling speeds and types of cycling facilities.
Third, additional research is needed in relation to bicycle streets. Bicycle streets are implemented in increasing numbers and may be an option to serve flow cyclists on access roads However, there is large variation across current bicycle street designs and more research is needed to determine their impact on cyclist safety.
