In view of the increasing demand for environmentally friendly and sustainable transport options, cycling is becoming more and more important. A prerequisite for the promotion of cycling is a particularly well-developed, comfortable and error-tolerant cycling infrastructure. The safe and comfortable use of cycle paths is of particular importance due to the surface quality of the asphalt surface layers being customized to the requirements of cyclists. Different abilities, types of use, age groups and means of transport result in individual requirements for a cycle path. Cyclists demand a safe cycling infrastructure with direct, simple and fast guidance. In addition, there is a demand for even, non-slip cycle path surfaces that are suitable for all weather conditions, have low rolling resistance and a uniform appearance. The surface quality requirements are usually best met by a machine-made asphalt surface layer.
The typical asphalt concepts for cycle paths are often just modified versions of asphalt concepts for road surfaces that do not take sufficient account of the special requirements of cyclists. For this reason, the standard asphalts with a maximum aggregate size of 5 mm have been optimized regarding the required surface properties. On the other hand, a new, innovative approach has also been designed in which the individual requirements for the surface properties are to be better taken into account by selecting a maximum aggregate size of 3 mm. Based on the concept idea, seven different asphalt variants made of asphalt concrete for surface courses and stone mastic asphalt with 5 mm and 3 mm maximum grain size were produced and tested in the laboratory.
To verify the individual demands of cyclists on the asphalt variants, a test program with comparative laboratory tests to evaluate the surface properties was set up and implemented. The results showed a tendency to improve the surface properties by selecting a smaller maximum aggregate size. The most promising variant was identified. It was determined that the principle of stone mastic asphalt with a chipped aggregate and a polymer-modified binder is the most effective when using a 3 mm maximum aggregate size. The results were put into practice on 18.09.2023 in Weyhe-Dreye on a dyke cycle path. This was followed up by a user survey and a follow-up laboratory test. Both confirmed the expectations placed on the project.
In summary, the choice of a smaller maximum aggregate size offers a promising opportunity to optimize the surface properties of asphalt surface courses for cycle paths and thus better meet the requirements of cyclists. In addition, aspects of sustainability should also come into focus. One possibility is to use recycled material in the production of asphalt and thus use resources more efficiently.