Modeling Framework for Capacity Analysis of Freeway Segments: Application to Ramp Weaves

Abstract

This research proposes a new modeling framework for the analysis of freeway segments. The framework provides a continuum from the operation of ramp weave segments to an equivalent basic segment serving the same traffic with the same number of lanes and free-flow speed. This approach distinguishes between congestion effects caused by high v/c ratios from turbulence caused by merging, diverging, and weaving traffic, thus greatly simplifying the model form, and its extensibility to other freeway segment types. The paper presents an application of this new framework to the analysis of ramp weaves, which were not sufficiently sampled in the development of the HCM6 methodology. The proposed model is shown to be superior to the HCM6 method both in relation to explaining field observations of speeds and in its simplicity in application. The results include a new formula for capacity estimation that is highly sensitive to segment length, and a speed estimation model that converges for low weaving volumes or at very high weaving segment lengths to that observed at a basic segment. Because the proposed model is calibrated with data mostly from North Carolina, it is recommended that data at additional sites be included in a larger calibration effort to ensure its applicability to a broader set of weaving segment configurations.

Using single and multiple unmanned aerial vehicles for microscopic driver behaviour data collection at freeway interchange ramps

“…The methodology, which consists of only three steps, can be followed by users who are not versed in UAV operation to collect reliable microscopic traffic data over a long segment of a high-speed, high-volume road, especially when the site has challenging conditions in terms of road geometry (curvature and elevation differences) as well as having significant parts of the segment covered by shadow due to presence of trees and fences. Such difficulties have limited many researchers (e.g., Xu et al 2020) to only manual video image processing techniques. This paper, therefore, differs from previous UAV-based traffic-related studies in several aspects.…”

Influence of traffic flow of on-ramps on the mainline speed on freeways

“…In recent, the operation analysis methods of freeway ramp influence segments can be mainly summarized into regression analysis, theoretical analysis, and traffic simulation. Regression analysis relies on field traffic data to conduct statistical analysis and establish the relationships between geometric design factors and performance measures (Xu et al 2020 Interactions are dynamic in freeway ramp influence segments, and so the operating conditions on the ramp can have an impact on the operation of the freeway mainline. A variety of research on the influence of ramps is also ongoing.…”

“…Currently, most existing studies on the impact of freeway ramps have primarily focused on traffic flow behavior , Zhang et al 2023). The traffic flow operation analysis methods can be mainly summarized into regression analysis, theoretical analysis, and traffic simulation (Xu et al 2020, Bhatt et al 2022). The traffic speed of vehicles entering from on-ramps can be much lower than that of the mainline, which could cause drastic speed changes.…”

Estimating the Effects of Freeway Weaving Section Length on Level of Service Based on Microsimulation

“…Some studies found that the manual underestimates the capacity of weaving sections when the VR is high (Skabardonis and Mauch [ 2 ], and Skabardonis et al [ 3 ]). Ahmed et al ( 4 ) and other studies (Xu et al [ 5 ] and Rouphail et al [ 6 ]) showed that the US-HCM speed estimation method has a lack of sensitivity to weaving length. Compared with the empirical analyses, respectively from NGSIM trajectory data, camera-recorded video data, and loop detector data, it has been found that the deficiency of the US-HCM is that the manual only improved the density by 6.3%, even though the length was quadrupled.…”