Field Experiment of Auxiliary Overtaking Lane Operation on the Four-Lane Expressway Section in Japan
TATSUO HAYAKAWA, Central Nippon Expressway Company LimitedShow Abstract
Hiroyuki Konda, Central Nippon Highway Engineering Nagoya Co., Ltd.,
Takashi Ishida, Highway Planning, Inc
Yasuhiro Nonaka, Highway Planning, Inc
Hideki Nakamura, Nagoya University
On intercity expressways in Japan, a general rule of driving in the outer lane is not complied well, and the road space is not efficiently being used in the section where the climbing lane is implemented to separate relatively slower traffic from main lanes. As a result, the quality of service of traffic flows even under the uncongested traffic condition is poor in general. To address this issue, this study analyzed the effect of an alteration in lane operation from the climbing lane to auxiliary overtaking lane from the viewpoint of traffic smoothness and safety. The result showed that lane traffic flow on the outer lane increased and lane speed distribution is significantly classified through this trial. Furthermore, reduction in the risky overtaking behavior from outside lane was identified. It can be concluded that this operation providing opportunity to overtake slower vehicles can significantly improve the level of service of traffic flow as well as safety on expressways.
The Effect of the Geometric Turning Radius on Vehicle Speeds at Urban Non-Signalized Intersections as a Safety Indicator
Yousteena Bocktor, McGill UniversityShow Abstract
Bismarck Ledezma-Navarro, McGill University
Luis Miranda-Moreno, McGill University
Turning maneuvers (left or right) and related treatments have been studied given their safety implications. However, a few studies have examined the effects of the designed curb turning radius. With the help of modern data collection techniques, this study aims to fill the gap presented in the literature on the investigation of the safety of local urban non-signalized intersections using the operating vehicle speed measures derived from observed video trajectory data. Using 35 non-signalized intersections in Montreal with turning radii less than 10.0 meters, video data was collected and processed using commercial software to obtain speed measures. The software utilizes computer vision and deep learning techniques to obtain the trajectories of all users. Over 75,000 users (motorists, cyclists and pedestrians) were detected and motorized vehicles (6906 cars, buses and trucks) were used for the purpose of this study. A random effects linear regression model was run on the speed data and the geometric measures, with an error factor on the intersection level in an aggregated and disaggregated approach. A significant statistical association between radius and speeds observed for aggregated data. For an increase of 1 meter in the turning radius, an increase of 0.775 kph for the 85th speed and 1.208 kph for the median speed for all turns, thus, decreasing the safety of the intersection. However, the turning radius was not of significance for the 85th speed of right turning vehicles which implies further investigation is required.
Vehicle Speeds on Rural Four-Lane Highway Curves: A Cross-Sectional Study
Michael Pratt, Texas A&M University, College StationShow Abstract
Srinivas Geedipally, Texas A&M Transportation Institute
Minh Le, Texas A&M Transportation Institute
Research has consistently shown that horizontal curves are often associated with increased crash rates compared to similar tangent highway sections. These crashes are often related to speed and difficulty judging the severity of the curve. Curve speed models are used for a variety of applications, including assessing operational characteristics, evaluating design speed, conducting spot safety analyses, and setting curve advisory speeds. However, most of the documented curve speed models apply to rural two-lane highways, while relatively few models have been developed for rural multilane highways. The objective of this paper is to document models that have been developed for several types of rural four-lane highways, including undivided highways, divided highways, and freeways. The authors developed models that account for geometric characteristics like curve radius, superelevation rate, and deflection angle, as well as operational characteristics like approach tangent speed. These models were calibrated using a database of about 98,000 vehicles across 32 horizontal curve sites.
Effects of Operating Speed and Traffic Flow on Severe and Fatal Crashes Using the usRAP Methodology and Field Data Verification
Fahmid Hossain, University of UtahShow Abstract
Juan Medina, University of Utah
This paper explores the effect of operating speed and traffic flow on roadway safety in light of the methodology provided by the usRAP. Different from traditional approaches, usRAP produces a systemic expected roadway safety performance, specifically the likelihood of being involved in a severe or a fatal crash, that is purely derived from roadway, roadside, and traffic characteristics, without need for detailed historical crash data. Data from over 900 miles of segments coded using the usRAP protocols and 5 years of crash data were used to examine changes in expected safety performance with changes in operating speed and traffic volumes. Speed and flow emerged as candidates for initial exploration as their effect is explicitly considered in the usRAP formulation for all crash types. The usRAP methodology produced a gradual decrease in the estimated safety performance of roadway segments with an increase in the operating speed, and such trends followed similar trends found in the field. Effects of traffic flows changes were not evidenced to be consistent in the field and did not produce large changes in the expected safety performance in usRAP either. Crash data is examined on the basis of a risk ratio that considers the relative frequency of severe and fatal crashes to the exposure of a given segment group, as well as star rating scores and star ratings from usRAP outputs. This study is part of a larger study to complete data collection and analysis of all state-maintained and federal-aid roadway system in Utah.