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Planning and design

Fault tolerant cycling infrastructure

Ruhr cycling highway in Mülheim
Ruhr cycling highway in Mülheim © Mmflooki via Wikimedia CC-BY-SA-4.0
In principle, infrastructure for cycling should be free of obstacles and danger spots in order to ensure safe and speedy cycling. In reality, however, it is precisely the paths for cycling that have widespread deficiencies, so that so-called single bicycle accidents can occur (obstacle collision, fall etc.).

Introduction

The bicycle as a means of individual transport should be available to people of all ages and physical abilities around the clock, all year round. The infrastructure for cycling should, as a matter of course, be free of obstacles and danger spots, as is the case for motor vehicle traffic, in order to ensure safe and speedy movement. In reality, however, there are widespread deficiencies in cycling routes that can lead to critical situations (e.g. lack of illumination in the dark, slippery conditions, missing markings, poor surfaces, blind curves and crests, obstacles at the edge or on the route and lack of path widths). If these are misjudged by cyclists or dangers are recognised too late, so-called single bicycle accidents (single bicycle accidents) can occur.

The term "fault tolerant cycle path" was coined in the Netherlands and Belgium as "vergevingsgezind fietspad" (cf. e.g. here) Originally, it was mainly used in the context of elderly, visually or mobility impaired people, who are more often involved in so-called single bicycle accidents [Pol/Linssen 2020]. However, infrastructure that increases their safety is not only a safety gain for all other user groups, but at the same time increases the comfort for all cyclists. Furthermore, spacious, barrier-free paths also benefit cargo bikes and other means of transport such as e-trekking scooters [CROW-Fietsberaad 2019].

Current discussion on increasing the safety of cycling infrastructure

The attention of cyclists is high, especially the areas to the left and right of the path are closely observed, the rear traffic area is mainly monitored acoustically. However, in many events, the perception of the traffic environment may not always be complete. Especially "for children and older cyclists, traffic participation involves particular risks due to developmental or age-related limited perceptual, motor and cognitive abilities" [Platho/Paulenz/Kolrep 2016]..

A look at the design guidelines for federal trunk roads shows that when new federal motorways are built, for example, it is a matter of course to design them in such a way that they are capable of forgiving human error - despite very high speeds and heavy traffic. Motorways are monitored and maintained around the clock, e.g. with winter road maintenance and other control drives. Curves and gradients are clearly laid out, and access and exit roads are designed to be spacious. The lane widths are generously dimensioned, at the side edges of the carriageways there are safety facilities such as safety strips, crash barriers, wide verges, retroreflective and physically tactile markings, large signposts and, last but not least, heated bridges that prevent accidents due to icy conditions.

Clearly designed „fault tolerant“ trunk road
Clearly designed „fault tolerant“ trunk road © Alexander Hunger

Good standards usually apply to urban roads as well. For example, the carriageways of main urban roads are brightly illuminated at night, and surfaces and dimensions allow safe travel even at higher speeds. Regular cleaning and winter services eliminate hazards caused by dirt, wetness, slippery surfaces, snow and ice.

These standards rarely apply to the paths in the side space on which pedestrian and bicycle traffic takes place. They do not always have adequate lighting or only insufficient clearance. Often, dense tree canopies also prevent adequate lighting at night. Large puddles of water, leaves in autumn, snow and ice in winter, poor surface conditions, hardly recognisable kerbs, steel bollards [Fietsersbond 2020] and a general undersizing, often with no possibilities to take evasive action to the left and right, make safe cycling difficult - especially on still unfamiliar terrain [CROW-Fietsberaad 2020a]. The clear alignment of cycling facilities is often not easy to follow and is made more difficult by the installation of safety boxes, traffic lights, signs, lampposts, railings, the presence of smooth tree grates and many other obstacles, including parked cars.

Fehlerverzeihende Infrastruktur?
Fehlerverzeihende Infrastruktur? © Alexander Hunger

Many main cycling axes in agglomerations run on cycle lanes and now also in cycle zones. In such sensitive areas, modal filters (easily crossable and visible for cyclists) should prevent motorists from using these areas as a sneak path. Here, too, potential hazards (dooring due to suddenly opening car doors (cf. also bicycle portal), many pedestrians crossing) must be minimised by structural and design measures.

In the case of out-of-town cycle paths with two-way traffic on one side of the road, cyclists are often blinded by oncoming vehicles at night. Here, cyclists particularly miss - despite now good bicycle lighting on most modern bicycles - retroreflective safety markings, wide verges, shark tooth markings at junctions (possible according to the new StVO) and other safety features that are already used in some cases on cycle lanes (e.g. centre markings, large pictograms, alternative routes, clear lines and signage). Great importance should also be attached here to adequate lighting, in sensitive areas taking into account the minimisation of environmental pollution, e.g. through light pollution. Self-luminous materials [Mak 2019] that store daylight have also been tried out. However, these are not always convincing, especially when cyclists are travelling with bright lights. Studies with visually impaired people showed that wide, profiled light-dark markings (black and white) are perceived best.

Straßenbegleitender Zweirichtungsradweg mit Abzweigung ohne Markierungen bei Dunkelheit und bei Tageslicht.
Straßenbegleitender Zweirichtungsradweg mit Abzweigung ohne Markierungen bei Dunkelheit und bei Tageslicht. © Alexander Hunger

Things that are taken for granted by motorists, such as conversations with accompanying persons, should in future also be possible for cyclists (in groups), especially in the leisure sector, without running the risk of getting stuck abruptly at bollards, in potholes and at other obstacles. When designing cycling infrastructure, the goal must be to enabeling the cyclist to cycle at one's own speed without stress in the case of heavy two-way traffic or fast and slow cycling traffic on the same paths.

Helle Radwegbeläge sind bei Dunkelheit auch ohne Randmarkierung gut erkennbar, die reflektierende Beschilderung ist gut sichtbar bei Nacht. Wichtig sind flache Übergänge zwischen Radweg und Bankett (Seitenraum).
Helle Radwegbeläge sind bei Dunkelheit auch ohne Randmarkierung gut erkennbar, die reflektierende Beschilderung ist gut sichtbar bei Nacht. Wichtig sind flache Übergänge zwischen Radweg und Bankett (Seitenraum). © Alexander Hunger

A good transport network also requires maintenance management. While motor vehicle carriageways in Germany are regularly recorded with special measuring vehicles, there is still no national standard for cycle paths and footpaths(cf. Cycling Portal and Cycling Portal). According to the Berlin transport administration, a new, nationwide standardised recording method is currently being worked on "together with the Federal Highway Research Institute (BASt) and the Road and Transport Research Association (FGSV), on the basis of which a corresponding condition recording for cycle paths and footpaths should also be carried out from around 2022" [SenUVK 2020]. A good cycling network also includes other measures such as "green waves" for cyclists, rain sensors at junctions, car-free bridges, spectacular cycle lanes or other highlights.

Cycling accidents in Germany

In 2019, of the total of 87,253 reported bicycle accidents with personal injury [Destatis 2020 and Cycling Portal] in Germany, around 22 % were single bicycle accidents. In 9.6 %, another person cycling and in 6.3 % a person walking were involved in the accident. Every year, around 400 cyclists die on German roads and paths. According to the survey "Mobility in Germany" (MiD), cyclists in Germany covered an average of 3.8 person-kilometres per day on bicycles in 2017 and made a total of 28 million trips per day [BMVI 2020]. More recent MOBICOR studies show that since the corona crisis, distances travelled by bicycle have once again increased significantly (e.g. by a third in Baden-Württemberg and more than double in Hesse, i.e. 6.9 km per trip). Whether for everyday or leisure purposes, the time spent on a bicycle is increasing and with it the use of the existing infrastructure. The safer this infrastructure is designed, the greater the likelihood that no one will come to harm.

Poller in einer Gasse – gut gemeint, aber gefährlich für Zu-Fuß-Gehende und Radfahrende.
Poller in einer Gasse – gut gemeint, aber gefährlich für Zu-Fuß-Gehende und Radfahrende. © Alexander Hunger

Various studies, e.g. based on surveys in hospitals, show that almost 70 % of bicycle accidents are not recorded by the police. In the case of single-vehicle accidents, the number of unreported cases is probably even higher, as victims who are not injured or only slightly injured do not usually go to hospital.

Findings from the Netherlands

In 2019, 203 cyclists died in the Netherlands (17 million inhabitants), according to the statistics authority there [CROW-Fietsberaad 2020b]. Among these cyclists, a quarter belonged to the 70-80 age group. 72% of all cyclists killed were over 60 years old. 65 people among all cyclists killed were on a pedelec. The Dutch try to design their cycling infrastructure not only to be comfortable and adapted to cycling volumes, but also to be fault tolerant: "To avoid solo cycling accidents, it is important that there are no obstacles to collide with, that the road layout is visually guided, e.g. by edge and axle markings on cycle paths, that the infrastructure is sufficiently wide, that the surface is even, firm, free of grooves/cracks and clean, and that road edges and curbs are forgiving" [SWOV 2020].

Fahrrad-Alleinunfälle in den Niederlanden 2009 nach Straßentyp, Reisekilometern in Orten mit über 20.000 Einwohner*innen.
Fahrrad-Alleinunfälle in den Niederlanden 2009 nach Straßentyp, Reisekilometern in Orten mit über 20.000 Einwohner*innen. © Verkeerskunde nach Fietsersbond 2009

Arten von Alleinunfällen im Zusammenhang mit der Infrastruktur.
Arten von Alleinunfällen im Zusammenhang mit der Infrastruktur. © CROW-Fietsberaad 2018

Senior citizens, children, need for research

According to the Federal Statistical Office, the proportion of people aged 65 and over in the total population rose from 15.9% to 21.4% (17.7 million) between 1998 and 2018. More and more senior citizens are not only travelling by car, but also as cyclists. The population-related risk of senior citizens to have an accident with a bicycle has increased by 83% since 1980. 15,578 senior citizens (29.2%) were involved in accidents as cyclists in 2018, of which 231 (22.1%) died. The fact that older people are particularly vulnerable in road traffic is also shown by the fact that 58.7 % of the cyclists who were involved in fatal accidents in Germany in 2019 were at least 65 years old [Destatis 2020].

Among the cyclists involved in accidents in 2018, the category "other driver errors" was the most strongly represented with 4,403 incidents; unfortunately, the cause "single-vehicle accident" due to inadequate infrastructure is not listed separately in the statistics and is therefore difficult to track. There is a need for research here, because single-vehicle accidents caused by infrastructure are an underestimated problem, as other problems such as alcohol abuse, driver incompetence, pedelec speeds that are too high, unsafe bicycles, incorrect clothing or unworn helmets are often emphasised in road safety work [e.g. DEKRA 2020].

Welcher Unfalltyp verursacht die meisten Krankenhauseinweisungen?
Welcher Unfalltyp verursacht die meisten Krankenhauseinweisungen? © Paul Schepers (SWOV) 2020

Of the children killed in road traffic in Germany in 2018, 26.6 % lost their lives on bicycles [Destatis 2020]. Driving errors are often the cause of accidents involving children. Fortunately, children are strongly underrepresented in accident statistics across Europe. Nonetheless, it is important to keep an eye on the very young and the very old in particular, as well as the newcomers who are still unsafe or inexperienced cyclists, and to take their specific safety needs into account. This benefits all cyclists. They are exposed to fewer hazards the smaller the amount of information they have to process on their journeys [Platho/Paulenz/Kolrep 2016]. In addition to the traffic rules, cyclists have to pay attention to a multitude of other dangers that motorists, not only due to generously dimensioned infrastructure, are not even confronted with due to the nature of their vehicle (wide tyres, no danger of tipping over): opening car doors, driving errors by drivers in front, infrastructural danger spots (wetness, edges, etc.), pedestrians suddenly crossing their path, dogs or similar.

Schlecht erkennbarer Übergang zwischen Wegrand und Seitenstreifen
Schlecht erkennbarer Übergang zwischen Wegrand und Seitenstreifen © Alexander Hunger

Infobox: Problematic road surfaces (danger of slipping when wet and slippery with frost).

  • Wooden bridges –> solution: roofing, epoxy resin mixtures with quartz sand, regular dirt particle and moss removal
  • Steel plates (excavation pit drive-over plates) -> solution: ribbed or rubber coating
  • Rails/tracks (if cyclists have to cross at an acute angle) -> avoidance of the acute crossing angle + rubber profiles
  • Slippery road markings in the direct driving and cornering area -> Solution: make the road non-slip
  • Smooth stone types -> solution: avoid or roughen afterwards

Potenziell unfallträchtig: Schienen/Gleise im Längsverkehr.
Potenziell unfallträchtig: Schienen/Gleise im Längsverkehr. © Alexander Hunger

Design principles

An ageing population, the growing popularity of pedelecs and the increasing volume of cycling lead to measuring design principles against the potential emergence of conflicts. The following five points are mentioned by Dutch experts:

  • Width: The wider a cycle path is, the lower the number of serious conflicts.
  • Visual guidance: The course of the road and obstacles at the edge of the field of vision must be observable. Edge marking is particularly desirable on relatively narrow two-way cycle paths, especially along unlit rural roads where cyclists are less able to perceive the contrast between the cycle path and the edge strip, for example due to glare from car headlights.
  • Feel: The use of materials that feel or sound different can make markings more perceptible. For example, an edge marking is easier to perceive if the lines have a tactile relief.
  • Height differences: Edges and lane edges should be designed to be forgiving: low and sloping or without height differences with only visual separation.
  • Obstacles: Obstacles along or on cycle paths, e.g. bollards, are to be minimised and - if unavoidable - designed to be "conspicuous and yielding".

Dicker, reflektierender Poller mit Aufmerksamkeitspflasterung im Annäherungsbereich (und hell gepflasterten Außenrändern).
Dicker, reflektierender Poller mit Aufmerksamkeitspflasterung im Annäherungsbereich (und hell gepflasterten Außenrändern). © Alexander Hunger

 

Infobox: Study on the visibility of a cycle path along the N631

In 2016, the Dutch province of Noord-Brabant had an extensive study carried out as part of a pilot project to evaluate marking types. Different types of markings were placed on ten different sections along the entire length of a cycle route, with a total of 14 different marking variants. The following materials were used:

  • Photoluminescent road markings (light emitting in the dark).
  • Lux Solar (LED lighting embedded in the road surface)
  • Luminescent reflectors for the road surface
  • Thermoplastic surface markings
  • Thermoplastic dot markings
  • 2K cold plastic
  • 3K cold plastic agglomerate
  • A380 high performance road marking film
  • Conventional road paint

From the point of view of road safety, the marking combination of thermoplastic dot marking and reflectors came out best of all (see photo).

Thermoplastische Punkt-Kennzeichnung + Reflektoren.
Thermoplastische Punkt-Kennzeichnung + Reflektoren. © van Osta/Tiellemans 2016

Recommendations from the study on the visibility of a cycle path along the N631 in the Dutch province of Noord-Brabant:

  • The first conclusion is that markings always have an added value compared to a situation without markings, i.e. doing a little is always better than doing nothing. White cold plastic markings become particularly visible when glass beads/reflective beads are added to them, which have a high reflective value.
  • With certain markings, certain individual aspects are rated better than others. For example, senior citizens stated that they found plastic/rugged markings very pleasant. LED lights embedded in the roadway were rated well when combined with edge markings, for example. For further experiments with marking types, it is recommended to try different types of markings in combination with each other.
  • In addition to good marking, it is pointed out that outdoor lighting would be desirable for social and road safety reasons.
  • Film footage and photos showed that strong bicycle headlights have a clear added value compared to weak lights. Targeted incentives to use a strong headlight are strongly recommended.
  • The degree of durability of the different types of marking depends on the manufacturer's claims. During the study it was not possible to assess this due to the short lead time. Applicators are advised to monitor the degree of wear of the different marking types in the coming years.

[van Osta/Tiellemans 2016]

Checklist: What should be considered when planning and operating cycling facilities?

  • As wide as possible (also usable for multi-lane bicycles, trailer combinations, etc.)
  • Predictable routing
  • Constant control and maintenance (measurement runs, test runs in the dark and wet)
  • Year-round usability, even in dark and wet conditions
  • Appropriate contrasting of the edges
  • Continuous obstacle clearance (clearance outline)
  • Identification of unavoidable obstacles and/or danger spots
  • Bumps (drainage, traffic calming) not on cycle paths
  • If possible, (ecologically) heat parts of the route that are often affected by slippery frost [cf. also Cyling Portal].

Conclusion

Already today, a lot can be done to make the infrastructure as safe as possible. Nevertheless, further research is needed - especially in German-speaking countries. For example, driving tests with different user groups (old, young, beginners, mobility-impaired) could be carried out during the day/night/wet to find out which markings, road surfaces, bollards and circulation barriers are best visible in bright light and in the dark [Hasselmann 2020]. As there is currently a lot of discussion about the use of physical separating elements made of plastic, steel and stone, as well as lane swings, e.g. to defuse junctions, this seems particularly important. With any type of lane fixtures, there is a need for observation of how these separating elements affect cycling safety in the medium and long term, but also the durability of the road infrastructure (e.g. frost damage).

Auf der Fahrbahn angelegter „geschützter" Radweg in Berlin-Steglitz
Auf der Fahrbahn angelegter „geschützter" Radweg in Berlin-Steglitz © Sabine Schulten

Literatur

[BMVI 2020]
Accessed on 08.01.2021
Bundesministerium für Verkehr und digitale Infrastruktur (2020)
[CROW-Fietsberaad 2019]
Accessed on 08.01.2021
CROW-Fietsberaad 2019
[CROW-Fietsberaad 2020a]
Accessed on 08.01.2021
CROW-Fietsberaad 2020a
[CROW-Fietsberaad 2020b]
Accessed on 08.01.2021
CROW-Fietsberaad 2020b
[Destatis 2020]
Accessed on 08.01.2021
Statistisches Bundesamt (2020)
[Fietsersbond 2020]
Accessed on 08.01.2021
Fietsersbond 2020
[Hasselmann 2020]
Der Tagesspiegel, Accessed on 13.08.2020
Hasselmann, Jörn (2020)
[Mak 2019]
Accessed on 08.01.2021
Mak, Alex (2019)
[Platho/Paulenz/Kolrep 2016]
Berichte der Bundesanstalt für Straßenwesen (BASt) (Hrsg.), Mensch und Sicherheit, Heft M 267, Bergisch Gladbach, Accessed on 08.01.2021
Platho, Christina; Paulenz, Andrea; Kolrep, Harald (2016)
[Pol/Linssen 2020]
Report zu Wissen und Wissenslücken um Fahrbahnmarkierungen auf Radwegen, Accessed on 08.01.2021
Pol, Mariëtte; Linssen, Carmen (2020)
[SenUVK 2020]
Accessed on 08.01.2021
Senatsverwaltung für Umwelt, Verkehr und Klimaschutz (2020)
[SWOV 2020]
Factsheet zu sicherer Infrastruktur für den Rad- und Fußverkehr, Accessed on 16.12.2020
SWOV 2020
[van Osta/Tiellemans 2016]
Provincie Noord-Brabant (Hrsg.)
van Osta, Anton; Tiellemans, Jacob (2016)
Meta Infos
Nummer
SPT 23
Date (Text as of…)
12. January 2021
Autor
Alexander Hunger, Tobias Klein (Deutsches Institut für Urbanistik)
Handlungsfelder NRVP
Infrastructure
Create and safeguard qualities
Planning and developing a cycling strategy
Road Safety
Topics
Research
Infrastructure
Quality management
Road safety
Keywords
Accessibility
Road surface
Roadway marking
Cycle track
Hazard point
Instandhaltung
Komfort
Qualitätsstandard
Sicherheitsempfinden
Accident
Wegewart
Winter services