The mass properties of a vehicle play a decisive role in its dynamics and characteristics and are fundamental for vehicle dynamics models and controllers. These values are not yet known for the vehicle class of the ultra-light velomobiles and similar multi-track bicycle vehicles. In the future, however, such vehicles could play a role in reducing the CO2 emissions generated by individual transportation. As a basis for vehicle dynamics modeling, accident reconstruction, and controller development for this vehicle class, this paper investigated ranges of mass properties and their influence on vehicle stability considering driver influence. In total, 13 vehicles (10 velomobiles and 3 trikes) were examined using different experimental setups. It was shown that most vehicles exhibited understeering behavior based on the center of gravity position and calculations of the static stability factor showed significantly lower rollover stability compared with conventional vehicles. The measured moments of inertia were used to develop and examine different approximation approaches for the yaw moment of inertia using conventional approaches from the passenger car sector and stepwise regression. This created the basis for parameter estimation from easily measurable vehicle parameters and provided the possibility to generate realistic parameter sets for vehicle dynamic models. Existing tests do not consider the influence of driver movements, such as pedaling movements or possible inclination of the upper body. This offers the potential for further investigations of the dynamic influences on the investigated variables.

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The causes of accidents involving nonconventional bicycle types have hardly been investigated in the literature to date. However, these vehicles could play an important role in reducing the CO2 emissions generated by traffic. As a basis for improving the driving safety of these environmentally friendly vehicles, this article presents the results of a survey on accidents and near-accidents of multitrack bicycle vehicles. More than 120 critical or accident situations of 86 drivers were analyzed. The situations are investigated with respect to the circumstances, the causes, and the consequences of the accidents using manual analysis and multiple correspondence analysis. A distinction is made between single accidents and accidents with another party. The aim of the survey is not to make statistically accurate statements on the frequency and probability of accidents, but rather to analyze the accident or near-accident circumstances. It is shown that the causes of single accidents are usually too high cornering velocities in combination with other factors such as road conditions. In the case of accidents with external involvement, the person who caused the accident is usually the other party involved. The accident opponent is in most cases a passenger car. Here the overlooking of the vehicles is the most frequent cause of accidents. Finally, possibilities to reduce the probability of accidents are briefly discussed for the different situations. As the research shows, most of the situations described occur on the road. This indicates that there are deficits in the bicycle infrastructure for the vehicles considered here. The results also indicate that there are deficits with regard to the perceptibility of the vehicles by other road users.