## 2 Literature Review
### Combined Curves' Geometric Design and Micro-Driving Behaviors  
[PERSON] [7] compared the speed difference between a crest curve and non-combined curve and found that the speed difference of the non-combined curve was lower than that of the crest curve. [PERSON] [16] used an interactive driving simulator, and the simulation results were used to evaluate the impact of concave combined and non-combined curves with different configurations on the driver's speed behavior. The study found that these curves have the same characteristics as the horizontal curves of concave combination. Among geometric design characteristics, how complex alignment and its adjacent sections affect deceleration and acceleration was the most important.  
[PERSON] et al. [17] classified combined curves into four types: upslope curves, downslope curves, sag curves, and crest curves. They used multiple linear regression models to estimate the impact of combined curves on lateral acceleration. They found that the inverse of the horizontal curve radius and slope severity affect all types of lateral stability, whereas length only impacts crest curves. [PERSON] et al. [12] examined speed changes on four combined curves: downslope, upslope, sag curves, and crest curves. The study found that the frequency of speed change behavior varied with the four combined curves. Additionally, the study revealed that different types of combined curves were impacted differently by the geometric design characteristics, resulting in varying degrees of significance of their influence on speed change. Finally, the impact of the neighboring section's geometric design parameters on speed change was considerable and variable. As a result, it is necessary to investigate the combined curves independently and consider their adjacent segments while designing the combined curves.  
[PERSON] et al. [18] analyzed the relationship between single-lane road departure crashes and roadside features using a negative binomial model for collision frequency and a multinomial logit model for collision severity. The results indicated that shoulder width, lateral clearance, and side slope conditions significantly influence road departure collisions. [PERSON] [19] found that evasive maneuvers and a lack of concentration or fatigue may lead to drivers leaving their travel lane. Geometric design features of roads and road edges, such as lane width and clear zone, play a significant role in whether human operational errors result in collision accidents. [PERSON] [1] analyzed the longitudinal acceleration distribution curve, including parameters like slope and curvature. Based on frequent isometric longitudinal acceleration measurements, he proposed a novel modeling method. The study found a positive correlation between the slope difference and the average curvature difference in the upslope and downslope with longitudinal acceleration. However, the average curvature exhibited a negative correlation with longitudinal acceleration.  
Previous research has not compared the distinguishing characteristics of various micro-driving behaviors comprehensively. This study compares speed change behavior and lane departure behavior, with a focus on the geometric design characteristics that influence them.