Institute of Transportation, MOTC

        In Taiwan, the limitation of road space and common mixed-traffic environment, curb-parking behavior will lead to a roadside interference and then cause the surrounding traffic flow to be intertwined and bring in conflict, thereby reducing road safety and the speed of passing vehicle. Previous studies mostly focused on the reduction of efficiency and capacity caused by curb-parking, and there were few studies on the aspect of traffic safety. Thus, this study will discuss the impact on road safety and passing speed of surrounding traffic flow that caused by curb-parking, from both macro and micro perspectives. Simultaneously, this research uses millimeter wave radar and image recognition technology to collect vehicle trajectory data, also extract 540 curb-parking and non curb-parking event, separately. Considering different traffic environment and different events, there may exist uncapable heterogeneity between events or vehicles, therefore, fixed-effect, random-effect and mixed-effect models are used to analyze and quantify the impact of on-street parking. It was found that, the interference of roadside parking will increase the behavior of surrounding vehicles due to deceleration, lateral displacement, and lane changing, then reducing the overall traffic efficiency of the outermost two lanes and increasing the occurrence of dangerous conflicts. Moreover, after in-depth micro-aspect discussion, it is found that curb-parking has even cause more impact. In addition, when the traffic volume of the mixed-traffic environment on the road section is greater than 1850 (veh./hr) or the proportion of motorcycle is between 55% and 65%, the negative impact of roadside parking on the surrounding traffic flow will be aggravated. This result can also provide a reference for future road section assessments, about whether on-street parking is allowed or it should be strengthen the ban in a specific period of time.