Pedestrians' Speed Analysis at Signalized Crosswalks

Pedestrian speed is essential for designing signal timings as well as for understanding pedestrian safety issues. This paper presents analysis of three types of pedestrian speeds (entry speed, crossing speed, and exit speed) at three signalized crosswalks in the State of Qatar. Pedestrian movements were tracked using TrafficAnalyzer software and data were analyzed to determine the effect of signal indications, crosswalk length, and crossing direction on pedestrian speeds. The results of this analysis showed that only 23.69% pedestrians crossed legally, during pedestrian green or pedestrian flashing green interval. Moreover, the pedestrian entry speeds were significantly affected by the pedestrian signal indications. Furthermore, the crossing speeds were positively correlated with crosswalk length for pedestrians crossing on green and red indications while pedestrian exit speeds were independent of crosswalk length but significantly affected by crossing direction. 2018 The Authors. Published by Elsevier B.V.Qatar National Research Fund, Qatar FoundationScopu

Safety performance of school buses in the State of Qatar

School buses and minibuses are one of the major modes of traveling for students in the state of Qatar. Many studies pointed to the fact that school buses travelling are safer for students than walking or car riding (Bolte, et al., 2000; Hinch, et al., 2002). For that reason, safety measures and performance of school buses in the State of Qatar should be studied and evaluated carefully and wisely. The project aims were done through merged qualitative and quantitative methods. Initially a safety checklist was constructed for school buses and a comprehensive schools map to evaluate of the current safety measures in school buses and to understand the conditions around the surrounding areas like the location of the bus stops and the availability of signage. Then, the second step focuses on conducting a survey for school bus drivers, school bus guides, students, and parents. Finally, the third steps compares between the school bus safety strategies followed in the State of Qatar and the strategies followed in other high income countries. The results of the field visits revealed many very important statistics for all surveys on the safety of school bus and the surrounding areas as well as the behavior of students and drivers. The results revealed that most of the parents are not happy with the safety while loading and unloading and with the safety procedures. In addition, 43% of school bus users didn't attend any training or workshops about the safety procedures in school bus. References: [1] Bolte, K. et al., 2000. Simulations of Large School Bus Crashes. [Online] Available at: http://papers.sae.org/2000-01-0469/ [Accessed 10 october 2014]. [2] Hinch, J. et al., 2002. School Bus Safety: Crashworthiness Research, Washington: National Highway Traffic Safety Administration.Qscienc

MIP models for minimizing total tardiness in a two-machine flow shop

We propose compact mixed-integer programming models for the NP-hard problem of minimizing tardiness in a two-machine flow shop. Also, we propose valid inequalities that aim at tightening the models' representations. We provide empirical evidence that the linear programming relaxation of an enhanced formulation yields an excellent lower bound that consistently outperforms the best bound from the literature. We further provide the results of extensive computational experiments that attest to the efficacy of the proposed MIP models. In particular, our computational study reveals that most of the 30-job hard instances are optimally solved using the proposed MIP models. Furthermore, we found that even much larger instances, with up to 70 jobs, can be solved for several problem classes. 2013 Operational Research Society Ltd. All rights reserved.Scopu

Exact method for robotic cell problem

Due to copyright restrictions, the access to the full text of this article is only available via subscription.This study investigates an exact method for the Robotic Cell Problem. We present an exact branch and bound algorithm which is the first exact procedure specifically designed for this strongly NP-hard problem. In this paper, we propose a new mathematical formulation and we describe a new lower bound for the RCP. In addition, we propose a genetic algorithm. We report that the branch and bound algorithm is more effective than the proposed mathematical formulation which can solve small sized problem. Also, computational study provides evidence that the genetic algorithm delivers reasonably good solutions while requiring significantly shorter CPU times to solve this problem

Pedestrians' Crossing Behavior at Marked Crosswalks on Channelized Right-Turn Lanes at Intersections

Unsignalized marked crosswalks are problematic locations from pedestrians' safety perspective. Although the priority rule at such locations is clear; pedestrians have the absolute right of way over vehicles, driver often compete with pedestrians over the right of way which risks pedestrian safety and impose extra delays on pedestrians. In developing countries, as concluded in many previous studies, vehicles usually do not give right of way to pedestrians, leaving them with the only choice to wait until an accepted gap is available. In Gulf Cooperation Council (GCC) countries where vehicles are the predominant mode of travel, pedestrians are receiving lesser priority. Drivers usually hijack the right of way from pedestrians which often causes safety threats. Therefore, pedestrians loose the reason for crossing at these designed locations pushing them to cross at arbitrary locations increasing their safety risk. This paper investigates influencing factors on the crossing behavior of pedestrians at marked crosswalks located on dedicated right-turn lanes. A study site from Doha, Qatar was selected for video recording and data analysis. A sample of 235 pedestrian observations was used for waiting behavior, crossing speed, accepted gaps, and driver yielding behavior analysis. The results showed that the waiting behavior was independent of pedestrian characteristics and relied only on the traffic characteristics. In addition, the average crossing speed was 1.43m/s and the gender, distraction, and group significantly affected the crossing speed. Beside, the distracted pedestrians and pedestrians crossing in groups accepted significantly larger gaps compared to undistracted and individual pedestrians. Moreover, about 15% of drivers yielded for pedestrians, yielding was irrespective of gender and mainly affected by the crossing direction. Consequently, innovative strategies in terms of engineering measures and awareness are needed to improve pedestrian safety at these locations. � 2017 The Authors. Published by Elsevier B.V.Scopu

Minimizing expected attacking cost in networks

A branch-and-bound algorithm is devised to determine the optimal attack strategy to disconnect a network where the objective is to minimize the expected attacking cost. The attacker cannot launch an attack if its cost is beyond his available budget or its probability of success falls below a threshold level. The proposed branch-and-bound algorithm includes, among other features, a dynamic programming-based lower bound as well as a preprocessing algorithm which aims at identifying unattackable links and removing irrelevant ones. Extensive use of the min-cut algorithm is made to derive valid upper bounds and to perform feasibility tests. Preliminary numerical implementation shows potential to provide exact solutions for medium-sized networks within reasonable time.King Saud University, Riyadh, Saudi Arabi

An overview of pedestrian signal setting and implementation in the State of Qatar

Pedestrian signal control is a main influencing factor on the Level of Service of crossing facilities and on the safety performance considering conflicts with vehicles. In signal design, pedestrian clearance time is a key design parameter for ensuring safe pedestrian crossing at signalized crosswalks. The performance of pedestrian signal control and its impact on pedestrian behavior in the Gulf Cooperation Council (GCC) Countries is rarely addressed in the literature. The characteristics of population, cultural diversity, as well as the extreme hot weather conditions, may lead to significantly different pedestrian behavior in terms of crossing manoeuvres (path and speed), compliance with signal control and interaction with vehicular traffic. This study reviews the pedestrian signal design practices in various countries and investigates the current signal settings along with their adequacy in the State of Qatar using empirical observations. The empirical analysis showed that the 85th percentile crossing times were longer than the provided Pedestrian Flashing Green (PFG) intervals at the observed crosswalks. Study sites are characterized with unrealistically long Buffer Intervals (BIs) which, from one side, provide sufficient time for pedestrians who started crossing during PFG to complete the crossing. On the other side, they encourage pedestrians to continue crossing after the end of PFG. Additionally, the speed analysis indicated that the observed 15th percentile speed was 1.22 m/s which is similar to the assumed design speed by the Qatar Traffic Control Manual QTCM (2015). Further, the analysis showed that pedestrian crossing speed during PFG or BI was significantly higher than that during PG. � 2017 The Authors. Published by Elsevier B.V.Scopu

A hybrid approach for identifying factors affecting driver reaction time using naturalistic driving data

The National Transportation Safety Board (NTSB) estimates that 80% of the deaths and injuries resulting from rear-end collisions could be prevented by the use of advanced collision avoidance systems. While autonomous or higher-level vehicles will be equipped with this technology by default, most of the vehicles on our roadways will lack these advances, so rear-end crashes will dominate accident statistics for many years to come. However, a simple and cost-effective in-vehicle device that uses predictive tools and real-time driver-behavior and roadway data can significantly reduce the likelihood of these crashes. In this paper, we propose a hybrid physics/data-driven approach that can be used in a kinematic-based forward-collision warning system. In particular, we use a hierarchical regularized regression model to estimate driver reaction time based on individual driver characteristics, driving behavior, and surrounding driving conditions. This personalized reaction time is input into the Brill's one-dimensional car-following model to calculate the critical distance for collision warning. We use the Second Strategic Highway Research Program (SHRP-2)'s Naturalistic Driving Study (NDS) data, the largest and most comprehensive study of its kind, to model driver brake-to-stop response time. The results show that the inclusion of driver characteristics increases model precision in predicting driver reaction times.This publication was partially supported by a grant from the U.S. Department of Transportation , Office of the Secretary of Transportation (OST), Office of the Assistant Secretary for Research and Technology under Grant no. DTRT12-G-UTC16 and a grant from Qatar National Research Fund (QNRF) under Grant no. NPRP8-910-2-387 . The findings and conclusions of this study are those of the author and do not necessarily represent the views of the VTTI, SHRP 2, the Transportation Research Board, or the National Academies. Furthermore, the contents of this chapter reflect the views of the author, who is responsible for the facts and the accuracy of the information presented herein. The U.S. Government assumes no liability for the contents or use thereof.Scopu

Empirical Study on Pedestrian Signal Design and Compliance in the State of Qatar

To ensure safe crossing manoeuvres at signalized crosswalks, the pedestrian delays and allocation of sufficient pedestrian green and flashing green times should be considered at design stage. The pedestrian signal settings in the State of Qatar were analyzed through empirical observations of eight crosswalks. Video recording technique was used to record the pedestrian movements and signal settings at selected crosswalks. The results indicated that excessive delays resulted in low compliance rates at all crosswalks and the signal phasing affected compliance rate. Moreover, the analysis of crossing speed indicated that the speed (1.2 m/s) currently specified by the Qatar Traffic Control Manual, 2015 for determining clearance time is sufficient for safe crossing. In addition, the results of speed analysis indicated that the gender, type of pedestrian signal display, and crosswalk length affect the crossing speed of pedestrians. A comparison of crossing times with the provided signal timings indicated that a lower pedestrian flashing green is provided at all sites, and excessively large buffer intervals are available. These results demonstrate the urgent need to modify signal settings to enable more opportunities for walking and legal crossings. It is recommended that pedestrian signals should be always activated based on the applied phasing plan without the need for pressing the push buttons. These push buttons can be used to recall early pedestrian green to reduce their waiting time. Furthermore, at major crossings, countdown timers showing time remaining for PG should be installed to improve compliance rates.This publication was made possible by an NPRP award [NPRP 8-365-2-150] from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. The authors acknowledge that the HCM delay model used is based on uniform arrival rates of pedestrians and it is not validated for Qatari conditions, which need to be investigated in the future.Scopu

Exact methods for the robotic cell problem

This paper investigates an exact method for the Robotic Cell Problem. We present a branch-and-bound algorithm which is the first exact procedure specifically designed with regard to this complex flow shop scheduling variant. Also, we propose a new mathematical programming model as well as new lower bounds. Furthermore, we describe an effective genetic algorithm that includes, as a mutation operator, a local search procedure. We report the results of a computational study that provides evidence that medium-sized instances, with up to 176 operations, can be optimally solved. Also, we found that the new proposed lower bounds outperform lower bounds from the literature. Finally, we show, that the genetic algorithm delivers good solutions while requiring short CPU times