Driving style is the main cause of left-turn accidents at traffic intersections, and the study of the speed change of left-turning vehicles facing different driving styles of straight vehicles can effectively explain the causes of accidents. Therefore, field observations were made at three traffic intersections in Beijing's Changping, Haidian, and Pinggu districts, and the steering angles, speeds, and other indexes of the left-turning vehicles as well as the speed change of the straight vehicles were recorded by video. The observation time was selected as peak and off-peak hours on seven weekdays and four holidays. The driving styles of left-turning vehicles were categorized by steering angle and speed and compared with their effects on the speed of straight vehicles. The results show that when the left-turning vehicles are aggressive, most of the straight vehicles will keep the original speed on weekdays, which will easily lead to accidents; on holidays, most of them will choose to slow down. When facing conservative driving style, most drivers will choose to keep the original speed on weekdays, and still do so on holidays. It can be seen that under the influence of time, aggressive driving style may induce aggressive behaviors in interacting vehicles; while conservative driving induces aggressive behaviors in interacting vehicles under any time period. The results of the study may inform the prediction of potential consequences of mixed traffic, which may lead to better integration of self-driving cars into mixed traffic roads in the future.