# Analysis of Conflict Distribution Characteristics between Motor Vehicles and E-Bikes at Roundabouts
## 1 Introduction
### Traffic Characteristics at Roundabouts  
In addition, factors such as the personality and gender of cyclists, the waiting position, the bike's body weight, and traffic volume all have a significant impact on the cyclist's preferred waiting time and the risk of violations. Compared with the bicycle cyclist, the e-bike cyclist has a more sensitive perception for each risk factor [26]. Based on the survey of the non-motorized cyclists' traffic behavior at intersections, it is concluded that bicycles and electric bicycles with more probability to violate traffic rules cause a greater interference with motor vehicles. It is supposed that the behavior of running a red light has been tacitly approved as a normal phenomenon in people's consciousness leading to most violations being red-light running [27]. Factors that cause e-bike traffic accidents mainly include age, gender, car proportion, illegal behavior, and other factors [28]. Among them, illegal behavior can be divided into red-light running, drunk riding, carrying adults riding, and other factors [29].  
Based on the analysis of roundabouts in Australia and New Zealand, it was found that about 4 out of 5 of the e-bike accidents at roundabouts are caused by the motor vehicle driver failing to give way to the cyclist because sometimes the driver didn't notice the cyclists or misjudged their speed. As a result, it is proposed that measures to limit the motor vehicles' speed in roundabouts and increase the visibility of non-motorized lanes should be conducted [30]. In an investigation of 294 small and mini-sized single-lane roundabouts in Switzerland, average weekday motorized traffic was identified as a major factor in explaining bicycle accident occurrence at roundabouts; it was found that the radius of the central island, the location of the roundabout (intown vs. out of town), and the number of legs were significantly related to bicycle accident occurrence [31]. In a survey of roundabouts in Lund, Sweden, each roundabout was classified into two types, with or without independent non-motorized vehicle lanes. The survey results showed that roundabouts with independent non-motorized vehicle lanes have a lower accident rate. It is concluded that roundabouts with non-motorized lanes are safer [16]. A statistical analysis of accident data on 255 single-lane roundabouts in Denmark showed that the diameter of the center island of a roundabout and the bicycle facilities both have a great impact on the safety of cyclists. Regardless of the speed limit, when the center island diameter is 20-40 m or there is a separate bicycle lane, single-lane roundabouts are always safer than cross intersections [17].  
In summary, previous work has investigated the impacts of innovative technologies [32] and the safety issue of conflict-point based autonomous intersection management systems [33]. But this paper focuses on a more recent transportation issues on motor vehicle and e-bikes at roundabout. The above conclusions on bicycle accident mechanisms and the influencing factors of electric are mainly focused on single-lane roundabouts, conventional cross-shaped intersections, and human-powered bicycles. While research on e-bikes at roundabouts is limited, some relevant research on roundabouts mostly considers e-bikes and human-powered bicycles as a whole. Therefore, research exclusively for e-bike safety at roundabouts will be discussed in this paper. Based on traffic conflict technology, this paper explored the conflicts distribution between motor vehicles and e-bikes at roundabouts from the dimension of space and time. It then finds out the mechanism of conflict distribution at roundabouts, which could be expected to improve e-bikes' safety at roundabouts.