Review on the Main Characteristics of Freeway Merging Section

The merging section is considered an essential part of the freeway segment, and it is one of the causes of traffic congestion along the freeway. This study reviews the main characteristics of merging sections and the methods to reduce traffic congestion at the merging section. Several significant factors affecting the merging section were identified such as freeway capacity, length of merging section, speed, traffic volume, and traffic composition. The effect of these factors has been thoroughly reviewed in this study to investigate their influences on traffic operations at merging sections. The effectiveness of ramp metering (RM) and gap metering (GM) was also reviewed in this study. The results indicated a significant impact of some traffic characteristics at merging sections, such as the lane-changing behavior, heavy vehicles, and RM effect. Combined with RM, the gap metering mechanism can reduce the overall delay at merging sections up to 27% compared to RM alone.