## 5 Discussion
When determining the median opening length, the running speed and traffic capacity of the work zone should be taken into consideration; especially in areas with a large flow, the coordination of the traffic capacity should be noted to avoid the \"double bottleneck\" phenomenon. Due to the limitations of the experimental conditions, this experiment only studied the influence of the median opening length on the vehicle speed and the driving workload in a one-lane scenario. With the development of reconstruction and expansion projects, 2-3-lane median openings are increasingly applied in practical projects, and some scholars have studied these conditions. [PERSON] et al. used a driving simulator to analyze the relationship of vehicle speed, acceleration, maximum steering wheel speed and lane-changing trajectory with safety for different median opening lengths in the case of two lanes without separation, concluding that the opening length should be 90 m [33]; however, it is difficult for driving simulations to fully simulate the real situation, and they lack consideration of the impacts of different traffic conditions, road conditions, fatigued driving, opposing traffic and other factors on the drivers. [PERSON] et al. considered a two-lane opening length in the case of being unable to change lanes, in terms of traffic operation status, road capacity and time to collision; the results indicated that each index was relatively good with an opening width of 100 m [29]. At present, relevant studies have not reported actual measured data for the traffic operation status of 2-3-lane median openings, and have not carried out the relevant naturalistic driving experiments. Since the increase in the turning radius and vehicle running speed, separation types, vehicle lane changing, interaction between vehicles, etc., under multi-lane traffic conditions will all have an impact on the driving workload, more factors should be considered compared to one-lane scenarios when laying out the work zone. This can be focused on in future research. The driver's driving workload will change instantly with the external conditions, the driver's psychology, the vehicle operation, etc. The environment of standard freeway sections and the activity area are monotonous, with little interaction between vehicles and simple driving tasks, making drivers prone to driving fatigue. Relevant research has illustrated that, if the road traffic conditions do not change, drivers will experience driving fatigue after driving for 146-205 s (2.44-5.7 km) at a running speed of 60-100 km/h, which sharply increases traffic safety risks. Therefore, stimulation should be provided timely to enable the driver to resume a normal driving condition. Attention should be paid to the work zone layout to avoid excessive lengths of the activity area. In addition to the median opening, the average and standard deviation of the driving workload in the upstream transition area are both large, so drivers need to slow down, change lanes and adopt other driving behaviors in the upstream transition area, which is also a blackspot. However, the traffic operation state, driver's psychological characteristics, setting methods, etc., in other types of transition areas are not clear, and the relevant experiments are scarce; therefore, further pertinent studies are needed.