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Left turns may generate efficiency problems, which can be solved by appropriately prohibiting left turns. The goal of this paper is to propose a method for purpose of minimizing total travel times in urban road networks by prohibiting left turns. With left turn prohibition, the signal timing plan is optimized with the lane-based method because the method can adequately handle both signal timing optimization and lane assignment. The total travel time is calculated with link flows and link travel time being estimated with signal settings. As illustrated by numerical examples, prohibiting left turns reduces the total travel time of car traffic in road networks. As the left turn prohibition results can handle the randomness in the network, these results provide potential implications for congestion management. [ABSTRACT FROM AUTHOR]

Highlights • The mobility levels of TWSC, RAB, and SIG are estimated and compared. • Impacts of turning traffic & pedestrian demand on intersection delay are considered. • Selection charts for appropriate control strategy at intersections are developed. • Turning traffic at the major & minor streets affect intersections' performance. • Pedestrians negatively affect the performance of TWSC and RAB. Abstract The selection of proper control types at intersections at the planning stage is an important concern considering the difficulty in comparing the performance of different control types. Therefore, several manuals proposed selection charts to guide traffic engineers in identifying the control strategy that yields to the lowest delay and the highest level of service. However, most of these methodologies consider only total major and minor street traffic flows. They do not necessarily suggest to investigate the impact of turning traffic and pedestrian flows, which limits the applicability of their recommendations. Thus, this study aims to propose a procedure to assess the selection of the optimum control strategies among two-way stop, roundabout and signalization using average intersection vehicle delay as the evaluation criterion. The impact of turning traffic on the major and minor streets as well as the impact of pedestrians are integrated into the developed analytical methodology for the estimation of average intersection vehicle delay. A typical layout of isolated four-leg two-way intersection is assumed for the model development. It is concluded that turning traffic and pedestrians play essential roles in the performance of intersections. As pedestrian flow increases, signal control becomes prevailing over the other control types. [ABSTRACT FROM AUTHOR]

Introduction Understanding driver behavior is important for traffic safety and operation, especially at intersections where different traffic movements conflict. While most driver-behavior studies are based on simulation, this paper documents the analysis of driver-behavior at signalized intersections with the SHRP 2 Naturalistic Driving Study (NDS) data. This study analyzes the different influencing factors on the operation (speed control) and observation of right-turn drivers. Method A total of 300 NDS trips at six signalized intersections were used, including the NDS time-series sensor data, the forward videos and driver face videos. Different factors of drivers, vehicles, roads and environments were studied for their influence on driver behavior. An influencing index function was developed and the index was calculated for each influencing factor to quantitatively describe its influencing level. The influencing index was applied to prioritize the factors, which facilitates development and selection of safety countermeasures to improve intersection safety. Drivers' speed control was analyzed under different conditions with consideration of the prioritized influencing factors. Results Vehicle type, traffic signal status, conflicting traffic, conflicting pedestrian and driver age group were identified as the five major influencing factors on driver observation. Conclusions This research revealed that drivers have high acceleration and low observation frequency under Right-Turn-On-Red (RTOR), which constituted potential danger for other roadway users, especially for pedestrians. Practical applications As speed has a direct influence on crash rates and severities, the revealed speed patterns of the different situations also benefit selection of safety countermeasures at signalized intersections. [ABSTRACT FROM AUTHOR]

Ageing drivers experience a higher risk of intersection crashes because of their decrease in driving efficiency, including the decline in cognitive ability, head and neck flexibility, and visual acuity. Although several studies have been conducted to examine the factors associated with ageing driver crashes at intersections, little research has been conducted to examine the differences in the factors related to ageing drivers’ turning paths and intersection geometric features. This study aims to improve the safety of ageing drivers at intersections by identifying the maneuvers that are risky for them and tracking their turning movements at selected intersections. We find that ageing drivers experience more crashes at intersections than younger drivers, especially crashes involving turning movements. Furthermore, ageing drivers experience more crashes at unchannelized intersections compared to channelized intersections. In addition, this study finds that ageing drivers exhibit greater and more inconsistent offsets during turning movements compared to those of younger drivers at both channelized and unchannelized intersections. Ageing drivers also tend to make relatively sharper or tighter turns than younger drivers. Hence, transportation engineers and road safety professionals should consider appropriate countermeasures to reduce the risks of crashes involving ageing drivers at intersections. [ABSTRACT FROM AUTHOR]

Behavior of right turning vehicles in the context of safety is characterized by their use of turning indicators and compliance with the stop rule. They are influence by the width of the carriageway and the variation in volume on the major road with respect to the traffic moving in the near and far side direction. Other factors affecting the behavior are the speed and spacing between vehicles moving on the major road. Lack of adequate past knowledge on the effect of geometric variation in terms of road width and directional variation in volume on the safety of unsignalized intersections have provided the motivation for this study. This paper focuses on the many factors that affect the behavior of right-turning vehicles resulting into conflicts. A brief account of the unique indigenous maneuver termed as the “Weaving Merging Right Turn” (WMRT) is provided and its effectiveness with respect to conventional right turn is evaluated. Data of 39,016 vehicles collected on 10 sites between January and June 2014 was analyzed. Multiple accidents were observed only on sites which had near side traffic volume greater than far side traffic volume. This result remains consistent with sites having single as well as multiple lanes per direction on the major roads. The number of conflicts for vehicles performing the WMRT was 2.5 times less as compared to the conventional right turn. Moreover WMRT was found to be the maneuver of choice for right turning motorcyclists with 60% of them opting for it over the conventional right turn on intersections having major road width less than 9 m. None of the motorcyclists, which were involved in a traffic conflict, were observed to use their turning indicator. Moreover none of the motorcyclists, which experienced a traffic conflict, were found to comply with the stopping rule at sites with major road width less than 9 m. On sites with major road width greater than 9 m, 45% of motorcyclists, involved in a traffic conflict, complied with the stopping rule as compared to 79% by vehicles other than motorcycles. [ABSTRACT FROM AUTHOR]

When designing median openings at divided highway intersections, it is important to consider the impacts of simultaneous (noncrossing) left turning movements by vehicles from opposing directions. The AASHTO Green Book recommends minimum lengths of median opening for different design vehicles and median widths. These minimum lengths are calculated based on assumed control radii for left turns from the divided highway into the crossroad and vice versa, and do not account for accommodation of simultaneous left turns. The Green Book minimum median opening lengths can prevent the capability for simultaneous left turns under certain circumstances. This study uses simulated vehicle turning paths to define the minimum conditions for accommodating simultaneous left turns and proposes corresponding revisions to the Green Book guidelines. The new method consists of determining the required control radius as a function of median width and calculating the minimum length of median opening by equations based on geometric relationships. The paper also describes the limitation of the Green Book methodology in addressing median openings with left-turn lanes, which is resolved by application of the proposed method. [ABSTRACT FROM AUTHOR]

A simulation based on VISSIM and its external driver model dynamic link library (DLL) was used to investigate the efficiency and safety of a two-way left-turn lane (TWLTL) on roads with staggered intersections (SIs). The impacts of traffic volume, ratio of left-turn vehicles, and stagger distance on SIs and conventional cross intersection (CI) were simulated with the following results: (1) SIs with stagger distance shorter than 200 m show few advantages in terms of average delay over a CI irrespective of traffic volume and left-turn ratio; (2) In contrast, SIs with stagger distance longer than 200 m show advantages that, however, disappear with an increase in traffic volume and left-turn ratio; and (3) SIs show a significantly higher number of traffic conflicts than CIs, indicating that they have more serious safety problems. These results should help traffic researchers and practitioners decide whether it is feasible to establish SIs on existing roadways with TWLTLs and the appropriate stagger distance for SIs, as well as whether it is appropriate to change a road that has dense SIs into a TWLTL cross section. [ABSTRACT FROM AUTHOR]