# Lateral Oscillation Characteristics of Vehicle Trajectories on the Straight Sections of Freeways
## 2 Literature Review
### Design and Determination of Lane Width  
The width of the vehicle, the lateral safety clearance, and the lateral oscillation of the trajectory make up the three primary components of lane width. Each country's road design specifications or guidelines provide the recommended lane widths for various road conditions. For example, the standard highway design reference document in the United States suggested that highways have a lane width of 12 ft (3.66 m) and a lane width of 9 ft (2.74 m) may be used on sections with lower traffic volumes and design speeds [4]. According to Chinese highway technical requirements, the recommended lane width for highways is 3.75 m, although it can be reduced to 3.50 m when passenger cars are the predominant traffic [5]. The German Road and Transportation Research Association stated that the width of the right-hand lane, mainly used by heavy vehicles, should be 3.75 m, while the left lane can be set at 3.5 m [6]. The Transportation Association of Canada stipulated that the lane width of highways was 3.5 to 3.7 m [7], while the UK Highways Agency considered 3.65 m or 3.7 m to be the usual lane width [8]. In addition, the Transportation Research Board (TRB) determined that the standard width for freeway lanes is 12 ft (3.66 m), and it came to the conclusion that there is no direct impact on the free-flow speed when the lane width exceeds 12 ft [9]. It was advised that the lane width be set lower than the normal setting in the code because many academics believed that the current lanes are excessively wide. [PERSON] et al. [10] concluded that the Highway Capacity Manual (HCM) was obsolete for lane width adjustment and therefore developed a model to forecast how narrow lanes would affect traffic flow efficiency. [PERSON] et al. [11] studied the effect of lane width reduction on the overall safety performance of highways. The breadth of the left shoulder had a bigger impact on crash rates than the lane width, and it was discovered that the level of safety would be hard to increase when the lane width exceeded 12 ft. [PERSON] et al. [12] explored the effect of lane width reduction on freeway operational efficiency. They concluded that operating speeds were less changed between 12-foot and 11-foot lanes under identical conditions. In China, numerous cities are starting to retrofit and test narrow lanes. For instance, Shanghai compressed the lane width of an urban expressway from 3.25 m to 2.7 m, thereby creating an additional lane. According to the results [13], lane reduction improved capacity and conserved road space. Meanwhile, some previous studies have carried out pertinent investigations into the acceptable lane width. One way involved using the Bolyankov model from the Soviet era to control the lateral safety spacing between vehicles and between vehicles and curb strips in order to determine the proper lane width. [PERSON] et al. [14] modified the Bolyankov model by fitting the measured data and using the 85 th percentile velocity as the design speed. [PERSON] et al. [15] statistically analyzed the relationship between lane width and lateral safety distance, saturation flow, and other factors at urban road signal intersections using questionnaires and Delphi methods. In several studies, the impact of driving behaviors and traffic flow characteristics has also been taken into account while designing roadway alignments, including research on lane widths for safety purposes. [PERSON] et al. [16] quantified the effect of different lane widths on the crash frequency of vehicles in various types of accidents on urban freeways based on vehicle crashes and traffic flow data. The results showed that the standard-size lane (3.45 m) had the lowest crash risk. However, the comparison of the combined impact of various widths on the vehicle operating level is typically required for the refinement study of lane width. While regulating the variable in practice is more challenging, some researchers have also found a way to circumvent this problem by employing simulation or driving simulators.