## 4 Results and Analysis
### Affected Area of the Transition Area  
The reduction in lanes in the transition area resulted in significant changes in road and traffic conditions compared to the standard freeway section (S) and advance warning areas (A), which increased the driving workload. Most participants slowed down in advance to anticipate the potential traffic safety risks caused by changes in road and traffic conditions. When participants entered the advance warning area (A) from the standard freeway section (S), they noticed the warning signs, speed limit signs, and lane reduction signs and slowed down. As the road and traffic conditions had not changed, the reduction in speed was relatively small, and most participants maintained a higher speed in the first half of the advance warning area (A). As they drove to the middle and rear parts of the advance warning area (A), they began to be affected by the transition area and slowed down again. The distribution of the distance of vehicle deceleration points from the transition area varied depending on the lane closure form, as shown in Figure 11.  
Most participants chose to decelerate in the rear section of the advance warning area (A), and only a small number of participants chose to decelerate in the front section (A). Overall, the data had a log-normal distribution (K-S test, R\({}^{2}>0.9\)), and when there were more lanes, participants were more inclined to choose to decelerate earlier. When the experimental road had two lanes, the overall vehicle running speed was lower compared to when roads had three to four lanes; moreover, when the drivers saw the lane reduction sign, they knew that there was a transition area ahead and that the right lane would be closed, reducing the number of lanes from two to one. As the drivers had an accurate expectation  
Figure 10: Distribution of vehicle speed and driving workload in transition areas with different lane closure forms. (**a**) Vehicle speed and (**b**) driving workload. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Lane**} & \multicolumn{1}{c}{**Large Vehicle**} & \multicolumn{1}{c}{**Medium Vehicle**} & \multicolumn{1}{c}{**Small Vehicle**} \\ \hline \(2\to 1\) lanes & 1 & 23\% & 23\% & 54\% \\ \hline \multirow{2}{*}{\(3\to 2\) lanes} & 1 & 24\% & 13\% & 63\% \\  & 2 & 35\% & 28\% & 37\% \\ \hline \multirow{2}{*}{\(4\to 3\) lanes} & 1 & 5\% & 4\% & 91\% \\  & 2 & 34\% & 14\% & 52\% \\ \multicolumn{1}{c}{} & 3 & 59\% & 10\% & 31\% \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Composition of non-closed lane traffic with different lane closure forms. of the road conditions ahead, they could relatively calmly respond to the changes in road and traffic conditions, resulting in a later deceleration point. When the experimental road had three to four lanes, participants saw the lane reduction sign but did not know the specific number of lanes that would be closed; additionally, the overall vehicle running speed was higher, so participants were unable to accurately anticipate the changes in road and traffic conditions ahead and were more inclined to slow down early to avoid traffic safety risks. Based on the deceleration points of most participants, the 85 th-percentile deceleration point was selected as the upstream affected area of the transition area. The distances of the 85 th-percentile deceleration point from the transition area were 966.8 m, 835.2 m, and 683.6 m for four lanes, three lanes, and two lanes; therefore, the upstream affected areas of the transition area were 1000 m, 850 m, and 700 m.  
Under different lane closure forms, changes in road and traffic conditions in the transition area resulted in different increases in the driving workload. After the participants entered the activity area (C), the road and traffic conditions no longer changed, and driving workloads decreased and gradually returned to normal levels.