## 6 Conclusions  
This study provides an empirical analysis of vehicle merging behaviors in temporary highway work zones at a trajectory level. First, we used UAVs to record videos above highway work zones. Ten sites of recording locations and three types of highway work zones are included. With the help of a newly proposed vehicle trajectory extraction framework, OpenVTER, we transformed raw videos into trajectories and came up with a highway work zone dataset, the wzone dataset. We selected eight different locations of work zones and divided them into three scenarios for analysis. Besides the primary three-lane work zones, the other two scenarios included one for solid white lines and one for a reduced number of lanes. We first analyzed the merging characteristics with different traffic states in the first scenario. In light traffic conditions, the desired lane changing position with the most frequency is about 300 m from the taper, meaning that a significant portion of drivers makes an early merge before the work zone. Still, the trend in merge location in heavy traffic was the opposite of that in light traffic. The gap and merge speed findings were consistent with intuition and previous studies. And the average lane speed decreased from the merge lane to the outside lane under light traffic conditions; in the other case, the opposite was observed. In another case, the basic scenario was compared with the other two scenarios to explore the merging behavior in different work zone layouts. When replacing the white dashed line with the solid lines, most merging locations did not appear to advance, while when reducing one lane, the proportion of early merge increased. The most critical difference in merging characteristics was the lane speed distribution and the impact on target followers. The speed of the through lane was the lowest, which was not consistent with the regularity found in the basic scenario. The two-lane highway work zone led to the most considerable speed reduction of the target follower, and the speed reduction and finishing speed of the merging vehicle were nearly linearly distributed. This study presented a high-resolution temporary highway work zone dataset and some empirical analysis of merging characteristics in different scenarios. The findings of this study offer valuable insights for improving traffic flow and safety in highway work zones. By analyzing merging behavior under different traffic densities, it becomes clear that dynamic lane management strategies--such as early merge or late merge systems--can be optimized based on real-time traffic conditions to reduce bottlenecks and improve flow. Additionally, the impact of work zone layout on traffic stability suggests that allowing more flexibility for lane changes, rather than imposing strict lane restrictions, could help minimize traffic oscillations and delays. Lastly, the study highlights the importance of mitigating the effects of merging on follower vehicles to enhance overall traffic safety, suggesting that better guidance on merging points can reduce sudden speed changes and lower collision risks. There is still some work to be carried out in the future to develop the research on merging characteristics in highway work zones. One limitation of this study is the geographic scope of the dataset, as the selected work zones were all from the same highway, which may limit the generalizability of the findings. Additionally, potential biases in site selection could influence the results, as work zones with certain characteristics (such as traffic volume or layout) were favored. Future research should aim to incorporate more diverse work zone scenarios, covering different geographic regions and road configurations. Expanding the dataset and developing predictive models for merging behavior could further improve the understanding and management of traffic in work zones. Conceptualization, Y.J. and X.Z. ; methodology, X.Z. and X.J. ; software, X.J. ; validation, L.Z. ; writing--original draft preparation, Y.J. and X.Z.