Ashim Kumar Debnath

Navigational Traffic Conflict Technique: A Proactive Approach to Quantitative Measurement of Collision Risks in Port Waters

Navigational safety analysis relying on collision statistics is often hampered because of low number of observations. A promising alternative approach that overcomes this problem is proposed in this paper. By analyzing critical vessel interactions this approach proactively measures collision risk in port waters. The proposed method is illustrated for quantitative measurement of collision risks in Singapore port fairways, and validated by examining correlations between the measured risks with those perceived by pilots. This method is an ethically appealing alternative to the collision-based analysis for fast, reliable and effective safety assessment, thus possesses great potential for managing collision risks in port waters.

Sustainable Urban Transport: Smart Technology Initiatives in Singapore

Achieving sustainability is a major goal of many urban transport systems. To attain an efficient, safe, and sustainable transport system, many innovative policies have been attempted in the past. Those policies often require smart technologies to assist in the implementation process and to enhance effectiveness. This paper discusses how sustainability can be promoted by embedding smart technologies in a modern transport system. In particular, this paper studies the transport system of Singapore to see how it is addressing sustainability through the use of smart technologies. Various technological initiatives in managing traffic flow, monitoring and enforcement, sharing real-time information, and managing revenues are discussed in light of their potential to address sustainability issues. The Singapore experience provides a useful reference for cities that intend to develop and promote a sustainable transport system.

Modelling Port Water Collision Risk Using Traffic Conflicts

Navigational collisions are one of the major safety concerns for many seaports. Despite the extent of work recently done on collision risk analysis in port waters, little is known about the influencing factors of the risk. This paper develops a technique for modeling collision risks in port waterways in order to examine the associations between the risks and the geometric, traffic, and regulatory control characteristics of waterways. A binomial logistic model, which accounts for the correlations in the risks of a particular fairway at different time periods, is derived from traffic conflicts and calibrated for the Singapore port fairways. Estimation results show that the fairways attached to shoreline, traffic intersection and international fairway attribute higher risks, whereas those attached to confined water and local fairway possess lower risks. Higher risks are also found in the fairways featuring higher degree of bend, lower depth of water, higher numbers of cardinal and isolated danger marks, higher density of moving ships and lower operating speed. The risks are also found to be higher for night-time conditions.

Hierarchical Modeling of Perceived Collision Risks in Port Fairways

Navigational collisions are one of the major safety concerns in many seaports. Despite the extent of work recently done on port navigational safety, little is known about harbor pilots’ perception of collision risks in port fairways. The study described in this paper used a hierarchical ordered probit model to investigate the associations between perceived risks and the geometric and traffic characteristics of fairways and pilot attributes. Perceived risk data, collected through a risk perception survey of Singapore port pilots, were used to calibrate the model. The intraclass correlation coefficient justified the use of the hierarchical model rather than an ordinary model. The results show higher perceived levels of risk in fairways attached to anchorages and in those featuring sharper bends and higher traffic operating speeds. Lower levels of risk were perceived in fairways attached to the shoreline and confined waters and in those with one-way traffic, a traffic separation scheme, cardinal marks, and isolated danger marks. The level of risk was also found to be perceived higher at night.

Gap acceptance behavior of mobile phone-distracted drivers at roundabouts

The use of mobile phones while driving is increasing at an alarming rate despite the associated crash risks. A significant safety concern is that driving while distracted by a mobile phone is more prevalent among young drivers, a less experienced driving cohort with elevated crash risk. The objective of this study was to examine the gap acceptance behavior of distracted young drivers at roundabouts. The Center for Accident Research and Road Safety–Queensland Advanced Driving Simulator was used to test participants on a simulated gap acceptance scenario at roundabouts. Conflicting traffic approaching from the right of a four-legged roundabout was programmed to show a series of vehicles with the gaps between them proportionately increased from 2 s to 6 s. Thirty-two licensed young drivers drove the simulator under three phone conditions: baseline (no phone conversation), a hands-free phone conversation, and a handheld phone conversation. Results show that distracted drivers started responding to the gap acceptance scenario when they were closer to the roundabout and they approached the roundabout at slower speeds. These drivers also decelerated at faster rates to reduce their speeds before gap acceptance compared with nondistracted drivers. Although accepted gap sizes were not significantly different across phone conditions, differences in the safety margin at various gap sizes—measured by postencroachment time (PET) between the driven vehicle and the conflicting vehicle—were statistically significant across phone conditions. PETs for distracted drivers were smaller across different gap sizes and suggest that a smaller safety margin was accepted by distracted drivers compared with nondistracted drivers.

Modelling Collision Potentials in Port Anchorages: Application of the Navigational Traffic Conflict Technique (NTCT)

Despite the extent of works done on modelling port water collisions, not much research effort has been devoted to modelling collisions at port anchorages. This paper aims to fill this important gap in literature by applying the Navigation Traffic Conflict Technique (NTCT) for measuring the collision potentials in anchorages and for examining the factors contributing to collisions. Grounding on the principles of the NTCT, a collision potential measurement model and a collision potential prediction model were developed. These models were illustrated by using vessel movement data of the anchorages in Singapore port waters. Results showed that the measured collision potentials are in close agreement with those perceived by harbour pilots. Higher collision potentials were found in anchorages attached to shoreline and international fairways, but not at those attached to confined water. Higher operating speeds, larger numbers of isolated danger marks and day conditions were associated with reduction in the collision potentials.

Driver beliefs regarding the benefits of reduced speeds

ABSTRACT Despite many studies of the benefits of reducing driving speeds for safety, vehicular emissions, and stress in driving, little is known regarding how drivers perceive these benefits and the factors influencing their beliefs. This article examines the factors influencing driver perceptions of the benefits attainable by reducing travel speeds. Driver perceptions of the extent to which reducing speed would lead to improved safety, lower emissions, and reduced stress and road rage were collected in an online survey of 3,538 drivers in Queensland, Australia. An analysis using seemingly unrelated regression showed that drivers of automatic cars and bicycle commuters more strongly agreed that lower speeds would provide these benefits than other drivers, whereas drivers who used premium fuel thought otherwise. Users of ethanol-blended fuel believed more strongly that reductions in speeds would reduce emissions. Young drivers less strongly agreed regarding emissions and stress than older drivers. Females, drivers of small cars, and those who drive frequently with passengers agreed more strongly that speed reductions would improve safety and reduce stress and road rage. These findings indicate a need to develop targeted educational and training programs to help drivers better understand these benefits to improve their willingness to reduce speeds.

Influence of Type of Traffic Control on Injury Severity in Bicycle–Motor Vehicle Crashes at Intersections:

Many studies have identified factors that contribute to bicycle–motor vehicle (BMV) crashes, but little is known about determinants of cyclist injury severity under different traffic control measures at intersections. Preliminary analyses of 5,388 police-reported BMV crashes from 2002 to 2014 from Queensland, Australia revealed that cyclist injury severity differed according to whether the intersection had a Stop/Give-way sign, traffic signals or no traffic control. Therefore, separate mixed logit models of cyclist injury severity (fatal/hospitalized, medically treated, and minor injury) were estimated. Despite similar distributions of injury severity across the three types of traffic control, more factors were identified as influencing cyclist injury severity at Stop/Give-way controlled intersections than at signalized intersections or intersections with no traffic control. Increased injury severity for riders aged 40–49 and 60+ and those not wearing helmets were the only consistent findings across all traffic control types, although the effect of not wearing helmets was smaller at uncontrolled intersections. Cyclists who were judged to be at fault were more severely injured at Stop/Give-way and signalized intersections. Speed zone influenced injury severity only at Stop/Give-way signs and appears to reflect differences in intersection design, rather than speed limits per se. While most BMV crashes occurred on dry road surfaces, wet road surfaces were associated with an increased cyclist injury severity at Stop/Give-way intersections. The results of this study will assist transport and enforcement agencies in developing appropriate mitigation strategies to improve the safety of cyclists at intersections.

Influence of Remotely Operated Stop–Slow Controls on Driver Behavior in Work Zones

Remotely operated devices for traffic control—portable traffic lights and automated flagger assistance devices—are used to improve flagger safety in a one-lane-each-way work zone with lane closure. Previous research has measured the effectiveness of these devices as driver compliance rates and driver understanding of the devices, but the effects of these devices on driver behavior have not yet been examined comprehensively. Therefore, the influence of remotely operated stop–slow traffic control devices on driver behavior was examined. Video-recorded traffic movements from a rural work zone in the Queensland state of Australia provided driver speeds, deceleration profiles, stopping behavior, and compliance rates for a set of remotely operated devices new to Australia: static red–amber–green lights, static red–amber lights, static red–amber arrow lights, and mechanical stop–slow signs. Pneumatic tube traffic counters were used to collect driver speeds before and after the devices, and an on-road driver survey was conducted to elicit driver understanding of the devices. Results indicated that drivers had difficulty understanding the new devices, particularly the amber light and amber arrow options (which confused drivers about their meaning—to stop or to go). The new remotely operated devices resulted in higher approach speeds, greater variability in approach speeds, and faster deceleration rates than the flagger method. The good compliance rates observed with the remotely operated devices imply that the devices could improve flagger safety by reducing flagger exposure to traffic; however, the negative effects on driver behavior might indicate an increased risk of rear-end crashes in the advance warning area.

Learning from insurance data: injuries to other road users in motorcyclist at-fault crashes

In multivehicle crashes involving motorcycles, the motorcycle rider is less likely to be at fault but more commonly severely injured than the other road user. Not surprisingly, crashes in which motorcycle riders were at fault and, particularly, crashes in which the other road users were injured have not received little research attention. This paper aims to address this gap in the literature by an investigation of the factors influencing the severity of injury to other road users in crashes in which the motorcyclist was at fault. Five years of data from Queensland, Australia, were obtained from a database of claims against the compulsory third party (CTP) injury insurance of the at-fault motorcyclists. Analysis of the data with an ordered profit model showed more severe injuries in crashes involving young (younger than 25) and older (older than 60) at-fault motorcyclists. Of the not-at-fault road users, the young, the old, and males were found to be more severely injured than were others. Injuries to vehicle occupants were less severe than those to motorcycle passengers. Crashes that occurred between vehicles traveling in opposite directions resulted in injuries that were more severe than injuries in crashes involving vehicles traveling in the same direction. While most existing studies have analyzed crash data reported by police, this study used CTP insurance data. Comparison of results indicates that CTP insurance data could be used as an alternative to crash data reported by police for gaining a better understanding of risk factors for motorcycle crashes and injury severity.