In traffic planning practice, the routing of bicycle traffic in confined spaces poses a particular challenge. The RADBEST research project, in which Cycle Competence members Salzburg Research, the Department of Geoinformatics at the Paris Lodron University of Salzburg and con.sens mobilitätsdesign were involved, looked for possible solutions. To this end, regulations and scientific studies were analyzed, experts were interviewed and comprehensive field studies were carried out using various survey methods in Germany, Austria and Switzerland. The results include concrete recommendations for traffic planning, road traffic regulations and guidelines.

Transnational cooperation in transport infrastructure research D-A-CH

Road cross-sections on main roads are sometimes not wide enough to install cycling facilities that comply with the guidelines. The aim is to make cycling safe and comfortable even in narrow areas. The rapid expansion of the cycling network and the closing of gaps in existing networks is a prerequisite for increasing the share of cycling in the D-A-CH region.

As part of the “Transport Infrastructure Research Cooperation D-A-CH 2022”, a transnational consortium from Austria, Germany and Switzerland, led by Salzburg Research Forschungsgesellschaft, developed evidence-based recommendations for cycling routes, especially in constricted road conditions, as well as technically sound considerations between various alternative solutions. RADBEST determined the status quo and problem areas in the three countries, carried out comprehensive field studies and derived solutions and recommendations for action.

The Holoscene research bike, stationary LiDAR sensors, Open Bike Sensor and MioVision Scout cameras were used in the field test, as here by con.sens mobilitätsdesign at the Währingerstraße location in Vienna.

Vehicle overtaking processes in the focus of research

Overtaking processes are individual events and depend on many factors. The research report mentions the following:

• Location-specific, largely constant parameters (from lane width to maximum permitted speed to bicycle traffic facilities)
• Situation-specific parameters (from dimensions of the overtaking cyclist to lighting conditions)
• Person-specific characteristics of cyclists (from driving line to visibility)
• Factors of motor vehicle drivers (from consideration to distance estimation skills to their own experience as cyclists)

A large variation in overtaking behavior and thus overtaking distances is therefore inherent in the system. The analysis of over 7,000 motor vehicle overtaking maneuvers by cyclists revealed that a significant percentage of overtaking maneuvers take place at close distances, which puts cyclists at risk or makes them perceive cycling as unsafe.

The representation of stress moments per polygon per second illustrates the increased stress perception of the test subjects, triggered by frequent overtaking. (Fig. 60)

Three possible solutions in relation to road width

A key solution is to take appropriate measures to ensure that motor vehicles overtake cyclists at a sufficient distance or otherwise refrain from doing so. Three scenarios were defined in the project for this purpose:

1. For carriageway widths between 6.5 – 9.5 m, wide cycle lanes and a narrow core carriageway can be used to ensure large overtaking distances (30 km/h).
2. This solution cannot be implemented for lane widths of less than 6.5 m. Here, “qualified mixed traffic” with pictogram chains / sharrows and a speed limit of 30 km/h is recommended as the preferred solution – possibly supplemented by a ban on overtaking by cyclists for motor vehicles or additional markings.
3. Recommendations are also made for selective bottlenecks and one-way lanes.

This diagram (Fig. 73) shows the possible solutions for cycling facilities in narrow road conditions as a function of road width. (Range of narrow lanes from 6.0 to 9.0 m)

Summary of the research team

According to RADBEST, there is no optimal solution for cycling in narrow conditions, but it is important to find the best possible solution in accordance with the relevant guidelines. It is not advisable to leave the routing of motor vehicles and bicycle traffic unchanged in mixed traffic on such roads. The involvement of all relevant stakeholders and the assessment of the specific situation are essential.

Illustration of various proposed solutions for cycling in confined spaces.

The researchers consider it necessary to carry out further investigations into the limits of use with regard to vehicle frequencies and route lengths as well as the effects of permanent cycling on cycle lanes. However, in order to implement the specific recommendations of RADBEST, changes to legislation and guidelines are also necessary.

Changes required to the StVO and guidelines in Austria

RADBEST therefore provides information on necessary changes to road traffic regulations and directives in Germany, Switzerland and Austria to enable the cycling solutions listed. The following points are listed for Austria in the final report.

Road traffic regulations:

• Inclusion of a ban on overtaking single-lane vehicles analogous to Germany
• Facilitation of a regulation of 30 km/h as the maximum permissible speed on main roads due to the guidance of bicycle traffic on the roadway in mixed traffic with motor vehicles.
• Setting of a high penalty for non-compliance with the overtaking distance and regular checks by the executive.
• Adaptation of the Austrian Road Traffic Regulations so that the minimum distance when overtaking also applies to cycle lanes (AT) and multi-purpose lanes (AT). In these cases, it is currently a case of “passing” and not “overtaking”.

It may also be necessary to specify that cars are permitted to drive permanently on the multi-purpose lane. Subject to a legal assessment, however, the current definition of the multi-purpose lane according to StVO §2 Para. 7a seems sufficient: “Multi-purpose lane (MZS): A cycle lane or a section of a cycle lane that may be used by other vehicles with special consideration for cyclists if the lane adjacent to the left of the multi-purpose lane is not wide enough for them.”

RVS guidelines:

• Wide multi-purpose lanes with narrow core lane (AT): In principle included in the RVS, but currently limited to roads with low traffic volumes or localized bottlenecks.
• Single carriageways: The remaining lane width next to multi-purpose lanes is currently 2.3 m as a rule and can be reduced to 2.0 m in exceptional cases.
• Adjustment of the dimensions and positioning of sharrows

Where were the overtaking maneuvers measured?

The 22 test routes were selected on the basis of different road categories and traffic conditions such as road width, type of cycling facility and vehicle traffic volumes:

Austria

Eisenstadt – Georgistraße, Klagenfurt – St. Veiter Straße, Pasching – Dörnbacher Straße, Pörtschach – Hauptstraße, Puch bei Hallein – Halleiner Landesstraße, Reifnitz – Wörthersee-Süduferstraße, Vienna – Währinger Straße, Wildon – St. Georgener Straße

Switzerland

Bühler/Gais/Teufen – Hauptstrasse, Marbach/Rebstein/Balgach/Widnau – Staatsstrasse, Sachseln – Brünigstrasse, Uznach – Zürcherstrasse, Walchwil – Artherstrasse, Zurich – Am Wasser; Badenerstrasse, Mutschellen-/Waffenplatzstrasse and Wehntalerstrasse.

Germany

Backnang – Eugen-Adolff-Strasse, Karlsruhe Durlach – B3, Singen – Hohenkrähenstrasse, Stuttgart – Schickhardtstrasse and Waldburgstrasse

Measuring overtaking maneuvers with the Open Bike Sensor: Starting from the seat post and minus half the width of the handlebars and the outside mirror of the vehicle, the Open Bike Sensor measures the lateral distance to the right and left. © Salzburg Research

RADBEST project information

Download the final report here: PDF | Project info at Salzburg Research
Download the presentation slides from 23.1.2025
Duration of the project was November 2022 to June 2024, presentation of results on January 23, 2025.

The research consortium consisted of Salzburg Research Forschungsgesellschaft, Paris Lodron University Salzburg, con.sens mobilitätsdesign and KFV (Kuratorium für Verkehrssicherheit) in Austria; OST – Ostschweizer Fachhochschule Rapperswil and Steinbeis Transferzentren GmbH at Karlsruhe University of Applied Sciences. RADBEST is an R&D service commissioned by the Austrian Federal Ministry for Climate Protection (BMK), the German Federal Ministry for Digital and Transport (BMDV) and the Swiss Federal Roads Office (ASTRA) under the program management of the Austrian Research Promotion Agency (FFG).

(All illustrations from RADBEST and the German Road Traffic Office).