Driver Response Research Articles

Assessing drivers' response during automated driver support system failures with non-driving tasks

IntroductionWith the increase in automated driver support systems, drivers are shifting from operating their vehicles to supervising their automation. As a result, it is important to understand how drivers interact with these automated systems and evaluate their effect on driver responses to safety critical events. This study aimed to identify how drivers responded when experiencing a safety critical event in automated vehicles while also engaged in non-driving tasks. MethodIn total 48 participants were included in this driving simulator study with two levels of automated driving: (a) driving with no automation and (b) driving with adaptive cruise control (ACC) and lane keeping (LK) systems engaged; and also two levels of a non-driving task (a) watching a movie or (b) no non-driving task. In addition to driving performance measures, non-driving task performance and the mean glance duration for the non-driving task were compared between the two levels of automated driving. ResultsDrivers using the automated systems responded worse than those manually driving in terms of reaction time, lane departure duration, and maximum steering wheel angle to an induced lane departure event. These results also found that non-driving tasks further impaired driver responses to a safety critical event in the automated system condition. ConclusionIn the automated driving condition, driver responses to the safety critical events were slower, especially when engaged in a non-driving task. Practical applicationTraditional driver performance variables may not necessarily effectively and accurately evaluate driver responses to events when supervising autonomous vehicle systems. Thus, it is important to develop and use appropriate variables to quantify drivers' performance under these conditions.

Randomized Phase III Study of Docetaxel Plus Cisplatin Versus Pemetrexed Plus Cisplatin as First-line Treatment of Nonsquamous Non–Small-cell Lung Cancer: A TRAIL Trial

IntroductionTo date, no prospective phase III trials have directly compared the efficacy of pemetrexed plus cisplatin (Pem-Cis) with docetaxel plus cisplatin (Doc-Cis) in patients with nonsquamous non–small-cell lung cancer. Materials and MethodsA total of 148 chemotherapy-naive patients lacking driver mutations were randomized into 21-day regimens of cisplatin 70 mg/m2 with either docetaxel 60 mg/m2 (n = 71) or pemetrexed 500 mg/m2 (n = 77) for ≤ 4 cycles. The primary objective was to assess the noninferiority of progression-free survival (PFS) for patients receiving the Doc-Cis regimen. The secondary endpoints were the response rates, overall survival, and toxicity profiles. ResultsPartial remission was observed in 24 (31.2%) and 24 (33.8%) patients in the Pem-Cis and Doc-Cis groups, respectively. The median PFS was 4.7 months (95% confidence interval [CI], 4.4-5.0) in the Pem-Cis arm and 4.4 months (95% CI, 3.7-5.1) in the Doc-Cis arm (P > .05). The median overall survival was longer in the Doc-Cis arm (13.3 months; 95% CI, 8.1-18.5) than in the Pem-Cis arm (11.7 months; 95% CI, 8.6-14.8; P > .05). Between the 2 arms, no significant difference was found in the subsequent treatments after failure of first-line treatment. The rate of grade 3 or 4 neutropenia and febrile neutropenia was greater in the Doc-Cis arm than in the Pem-Cis arm. ConclusionIn nonsquamous non–small-cell lung cancer patients lacking driver mutations, the PFS and response rates were similar between the 2 arms, and toxicity was tolerable, although adverse events and more severe toxicities were observed more frequently in the Doc-Cis arm.

Responses of drivers and motorcyclists to congestion charge

Abstract To effectively mitigate traffic congestion, many densely populated and well-developed cities worldwide decided to charge in-town traffic a congestion fee and the effectiveness of the congestion charge policy has been proven. However, a successful congestion charge scheme mainly depends on a clear understanding of urban travelers’ responses. To do so, this study aims to model behaviors of travelers, including car drivers and motorcyclists, in response to in-town congestion charge in Taipei City and to propose feasible in-town congestion charge scheme accordingly. Four possible choices of travelers are defined as: 1) Pay for the charge, 2) Shift to off-peak hours/Cancel the trip, 3) Shift to public transportation, and 4) Shift to other private modes. Due to the possible correlation among alternatives and the potential heterogeneity among travelers, Multinomial Logit model (MNL), Nested Logit model (NL) and Mixed nested Logit model (MXNL) are estimated and compared based on a large-scale post-mail questionnaire survey. A total of 5,906 valid questionnaires were returned, including 3,450 car drivers and 2,536 motorcyclists. Among them, a total of 355 drivers and 314 motorcyclists who have morning peak-hour commuting experiences in Taipei City were selected. The estimation results show the existence of correlation among alternatives and heterogeneity for car drivers. Additionally, motorcyclists are much more sensitive to the charge than car drivers. The proportion of drivers and motorcyclists who are discouraged by various congestion charges are also predicted based on the estimated model. Suggestions for implementation of congestion charge are then proposed accordingly.

The Effect of Trust on Driver's Response to Advanced Driver Assistance System and Its Affecting Factors: A Case Study of IMA

The Effect of Trust on Driver's Response to Advanced Driver Assistance System and Its Affecting Factors: A Case Study of IMA

Development and Evaluation of High-Speed Differential Warning Application Using Vehicle-to-Vehicle Communication

Connected vehicle (CV) technology has shown great potential in enhancing safety, mobility, and environmental sustainability of roadway transportation systems by enabling vehicles and infrastructure to exchange real-time information through wireless communications. The information available through CV technology has been used to develop a variety of onboard driver assistance tools and applications. This paper presents an innovative, safety-focused CV application called the high-speed differential warning (HSDW). The application identifies potential hazards resulting from high-speed differentials between HSDW-equipped vehicles (ego-vehicles) and surrounding remote vehicles and then provides alerts to drivers of ego-vehicles to help them take appropriate actions. In this research, real-world scenarios and parameters of the HSDW application are first identified. A driver response strategy for each scenario is then developed in consonance with findings from a public survey on the HSDW application. Next, a comprehensive evaluation of various scenarios is conducted with a well-calibrated Paramics traffic microscopic simulation tool set up for a real-world traffic network. Finally, the safety performance of HSDW-equipped vehicles, unequipped vehicles, and overall traffic is analyzed with the surrogate safety assessment model. Results demonstrate that the proposed HSDW application improves the safety performance of ego-vehicles without compromising the mobility and environmental sustainability performance of the overall traffic.

Strategies to Assist Drivers in Remaining Attentive While Under Partially Automated Driving: Verification of Human–Machine Interface Concepts

Visual inattention is a major concern with partially automated driving systems that assume vehicle steering functions. The safety concept for these systems capable of maintaining vehicle lane position and headway depends on an attentive driver who detects and appropriately responds to objects and events that are beyond the limitations of the sensors. Embedded within a proposed system are features designed to help drivers perform these functions and remain attentive to the driving environment. This study served to validate human–machine interface (HMI) strategies and concepts that can be applied to production-intent partially automated system HMI to achieve intended safety goals in assisting drivers to maintain attention to driving. Previous validation efforts, conducted as part of a NHTSA study, proved insufficient for verification of these driver performance functions since they relied on an incomplete version of alternative HMI concepts. The current study, with a sample of 25 licensed drivers, used approaches that more closely approximated the potential production-intent partially automated HMI concepts, including the introduction of consequences for failing to respond to alerts. Work was performed by using an advanced prototype capable of mimicking the basic functions afforded in a partially automated system. Driver responses to unexpected lane drift events were also examined. Results found that HMI concepts that introduce consequences for driver nonresponse situations substantially increase driver compliance to system cues, prompts, and alerts. Results of this study suggest that the potential production design partially automated system HMI concepts can assist drivers in maintaining their attention to driving.

Modeling Driver Behavior in Dilemma Zone under Mixed Traffic Conditions

Abstract When signal changes from green to yellow at a signalized intersection, often drivers become skeptical, whether to cross the intersection or stop without entering the intersection. Improper decision might lead to right angle collision or rear end collision. The area in which the drivers are skeptical is termed as dilemma zone or indecision zone. Most of the studies in the literature have investigated the dilemma zone driving behavior in homogeneous traffic conditions, but traffic in developing countries like India is heterogeneous containing various vehicle types, where vehicles vary in their physical dimensions and dynamic characteristics. The main motive of this study is to investigate the factors influencing the driver behavior in dilemma zone at signalized approaches in India under mixed traffic conditions. This study investigated the driver behavior by videotaping 398 driver responses at two signalized intersection approaches with different yellow durations. Binary logistic regression model is developed to represent the driver behavior in mixed traffic conditions. Vehicle type, which is a characteristic of mixed traffic conditions is found to have a significant impact on the driver’s decision process along with the vehicle speed, distance from the stop line and duration of yellow signal.

Evaluation of Right-of-Way Transitions at Signalized Intersections: Implications of Driver Behavior for Conflicting Through Movements

To improve traffic safety at signalized intersections, driver behavior associated with right-of-way transitions at signalized intersections must be quantified carefully. Video data from five intersections across Oregon were collected and transcribed; a total of 149 h corresponded to 3,474 vehicles responding to a circular yellow (CY) indication and 731 vehicles responding to a circular red (CR) indication. A mixed logit model was used to evaluate driver responses to CY and CR indications. Multiple linear regression was used to analyze the characteristics of red light runners (RLRs). Sufficiency of the red clearance interval was evaluated by considering the interactions of RLRs with vehicles on the conflicting approach. Developed models indicated that a 1-s increase in red time per cycle decreased the probability that a car would stop in response to a CY indication (by 41.4%) or a CR indication (by 9.0%). However, an increase in red time decreased the required duration of the red clearance interval. A 1-s red clearance interval generally was adequate for passenger cars, light trucks, and trucks at intersections up to 80 ft wide and at intersections with a red time of at least 60 s per cycle but rarely was sufficient for semitrailers in wider intersections with shorter red times. This observation is critical because semitrailers were more likely to be RLRs than were other vehicle types.

Driver brake vs. steer response to sudden forward collision scenario in manual and automated driving modes

In autonomous vehicle operation, situations may arise when the driver is required to re-engage in manual control of the vehicle. Whether the control handoff from vehicle to human is done in a structured or unstructured manner, the process may be affected by the driver’s state, i.e. distracted or not. The study reported here was designed to measure a non-distracted driver’s response to a sudden forward collision (FC) event, in which the driver would assume manual control of the autonomous vehicle. Three driving scenarios were investigated: autonomous vehicle driven with full collision avoidance support, autonomous vehicle driven without collision avoidance support, and vehicle driven in manual mode.Forty-eight volunteers participated in a simulator study conducted in VIRTTEX. It was found that, at handoff, (1) drivers in manual mode tended to use evasive steering, rather than braking, compared to drivers in both the autonomous modes, (2) between subjects variations in speed were higher for the automation with collision support condition than for the other two scenarios, (3) for both autonomous driving scenarios, drivers reaction times were longer than for manual driving. In some cases the driver response was so late and the distance remaining so reduced that crash avoidance might be unfeasible. At a minimum, results of this study suggest that drivers may benefit from appropriate driver assistance technologies when a crash imminent situation is suddenly encountered.

Critical values of driver response time and its impact on reducing reliability and safety in road traffic

Critical values of driver response time and its impact on reducing reliability and safety in road traffic

The Effect of Initial Molecular Profile on Response to Recombinant Interferon Alpha (rIFNα) Treatment in Early Myelofibrosis

IntroductionSuccessful treatment of early myelofibrosis (eMF), defined as patients (pts) with low or intermediate-1 (int-1) risk and ≥15% hematopoietic foci in the marrow biopsy, with rIFNα has been reported, but effects of driver and epigenetic mutations on outcomes were not considered. We now report results of our single center phase II study of 30 pts with primary (PM) or secondary (SMF) eMF, correlating the baseline molecular profile with response to rIFNα treatment.MethodsWe used WHO 2008 and IWG-MRT criteria for the diagnosis of PM and post-polycythemia vera MF (pPV MF) or post-essential thrombocythemia MF (pET MF), respectively. Prognosis was assessed using the Dynamic International Prognostic Scoring System (DIPSS). Response classifications were complete response (CR), partial response (PR), clinical improvement (CI), stable disease (SD), progressive disease (PD). Evaluation included history, examination, spleen size (cm below left costal margin), CBC and differential counts, routine chemistries, liver, renal, and thyroid function tests, marrow biopsy, cytogenetic and molecular genetic evaluations. Marrow specimens were stained routinely for morphology, reticulin, and collagen; fibrosis was graded using the European consensus system.JAK2, CALR and MPL mutations were detected and quantified by amplicon based next generation sequencing (NGS). NGS of 45 genes recurrently mutated in myeloid malignancies was performed on 25 of 30 baseline specimens, including ASXL1, IDH1/2, EZH2 and SRSF2, previously defined as high molecular risk (HMR) genes.Descriptive statistics were calculated and Fisher’s exact test used to explore the relationship between mutations and various results. Pts received either rIFNα-2b or peg-rIFNα-2a starting at a 5x105 to 1x106 units SC 3X wk or 45 to 90 mcg weekly, respectively; dose increase dependent upon tolerance and/or response.ResultsOf 96 pts with PM or SMF, 30 met study criteria, including 16 women and 14 men (med. dx age 58 yrs). Twenty-one had PM, 7 pPV MF, and 2 pET MF. Twenty-one pts were low risk, 9 int-1. Twenty-two were JAK2V617F(+), 6 CALR(+), and 2 MPL(+). All 7 pPV MF pts were JAK2(+). One pET MF was JAK2(+) and 1 CALR(+). Of PM pts, 14 were JAK2(+), 5 CALR(+), and 2 MPL(+).Med. rx duration has been 5.6 yrs and is ongoing. Clinical toxicity, grade 1 or 2, included mild depression, dry skin, cough, and myalgia. Hem. toxicity included anemia (grade 1-2: 17 pts), leukopenia (grade 1-2: 9 pts), and thrombocytopenia (grade 1-2: 10; grade 3: 2 pts). In these cases, rIFNα dose was temporarily reduced/interrupted until cytopenias resolved. One pt developed hyperthyroidism; treatment was discontinued.Of 30 pts, 2 (7%) had CR, 9 (30%) PR, 4 (13%) CI, 7 (23%) SD. Four (13%) had PD, and 4 (13%) died. Nine of 21 low risk pts had CR or PR, compared with 2 of 9 int-1. A small spleen at baseline was associated with better response in the absence of HMR abnormalities. Of 18 pts with slight or no splenomegaly, 11 had CR or PR, and of the non-responders, 2 had a HMR. Of 12 pts with significant or moderate splenomegaly, none had CR or PR, including 2 with a HMR. Follow up biopsies in 25 pts (83%) a reduction in reticulin fibrosis in 5, increase in 9, and stable in 10. Decrease in cellularity occurred in 12. There was no correlation between decrease in JAK2 allele burden, response, fibrosis, or spleen size.There was no correlation between driver mutations and response (Table). Pts with a HMR had worse responses; of 4 such pts, 0 responded, 1 remained stable, 1 progressed and 2 died. Specifically, pts with ASXL1 mutations seemed to do worse than those without it, although sample size precludes a definitive statement (p=0.19).ConclusionThis is the first study considering the effect of baseline mutation status on response to rIFNα treatment in eMF pts. 73% of pts improved or remained stable regardless of initial low or int-1 score or driver mutation, but spleen size and HMR adversely affected treatment response.Although baseline driver mutation status was not prognostically useful, a molecular profile should be obtained initially to identify HMR mutations, which negatively affect response to treatment including rIFNα. In 73% of selected cases, low dose rIFNα in eMF resulted in marrow reversion, regression of splenomegaly or disease stability with tolerable toxicity. Early treatment of MF with rIFNα in pts without HMR may prevent the development of marked splenomegaly, anemia, and florid myelofibrosis. [Display omitted] DisclosuresSilver:Incyte: Membership on an entity’s Board of Directors or advisory committees. Ritchie:Pfizer: Honoraria; Incyte: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Honoraria, Research Funding; Arian: Speakers Bureau. Roboz:Agois: Consultancy; Amgen: Consultancy; Amphivena: Consultancy; Astex: Consultancy; AstraZeneca: Consultancy; Boehringer Ingelheim: Consultancy; Celator: Consultancy; Celgene: Consultancy; CTI Biopharma: Consultancy; Genoptix: Consultancy; Janssen Pharamaceuticals: Consultancy; Junno: Consultancy; MedImmune: Consultancy; MEI Pharma: Consultancy; Novartis: Consultancy; Onconova: Consultancy; Pfizer: Consultancy; • Roche Pharmaceuticals: Consultancy; Sunesis: Consultancy; Teva: Consultancy. Orazi:Novartis: Honoraria. Tam:Millennium Pharmaceuticals, Inc.: Consultancy. Cross:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau.

An Exploratory Study of Driver Response to Reduced System Confidence Notifications in Automated Driving

An exploratory study in a moving-base simulator with 34 volunteers examined the effects of automated driving system reduced-confidence notifications on driver response. Reduced confidence in this context is defined as a system performance level that is lower than optimal, yet not so low as to disable the system. The threshold for such a level is essentially a policy decision based on perceived costs and benefits of keeping the automation engaged versus disengaging it. So, a reduced-confidence notification was designed to simply indicate that the driver should be especially vigilant to the increased potential to have to take manual control of the vehicle. An actual manual takeover request from the automated system would require the driver to take manual control of the vehicle. To investigate this, a 32-min highway driving scenario was constructed for this exploratory investigation that included 16 potential loss-of-lane tracking segments within this time frame. Three factors at two levels (low/high) each were crossed and presented in a between-subjects experimental design. One factor was system confidence/competence match, which refers to the ratio of the number of actual automation system failures over the number of reduced-confidence notifications. A second factor was the consequence of automation failure, i.e., drifting toward a busy traffic lane or drifting toward a wide shoulder. The third factor was detectability, or being able to see versus not see why the automated driving system began to drift out-of-lane. Data analyses indicated that automated driving with reduced-confidence notifications was judged to be both useful and acceptable regardless of the manipulated factors. However, the lowest incidence of preemption (i.e., manual takeovers prior to the start of a lane drift) was associated with low automation competence/confidence match and low detectability, regardless of consequences. It was also associated with responding later by some drivers. On the other hand, when the reduced-confidence notifications were perfectly matched with the need to manually takeover, there were fewer instances of delayed driver responses. Results are discussed in terms of “cry wolf” effects.

Early warning signals, nonlinearity, and signs of hysteresis in real ecosystems

AbstractEarly warning signals (EWS) might dramatically improve our ability to manage nonlinear ecological change. However, the degree to which theoretical EWS predictions are supported in empirical systems remains unclear. The goal of this study is to make recommendations for identifying the types of ecological transitions that are expected to show EWS. We conducted a review and meta‐analysis of published studies and comparative analysis of eight northeast Pacific Ocean time series to illustrate the importance of testing for nonlinearity in empirical EWS studies. We found that published studies demonstrating nonlinearity in ecosystem dynamics are more likely to support EWS predictions than studies with linear or undetermined dynamics. The northeast Pacific time series in our analysis were often too short for formal tests of nonlinearity, a common problem in empirical studies. To assess the evidence for nonlinear dynamics in these data, we tested for state‐dependent driver–response relationships consistent with hysteresis, a central feature of nonlinear ecological models. This analysis supported the results of the literature meta‐analysis. Four time series with driver–response relationships consistent with hysteresis generally supported theoretical EWS predictions, while four without evidence of hysteresis failed to support EWS predictions. Theoretical support for EWS is largely generated from nonlinear models, and we conclude that tests for either nonlinear dynamics or hysteresis are needed before employing EWS.

Особенности моделирования ситуаций для проведения испытаний по оценке тактико-психологической подготовленности сотрудников дорожно-патрульной службы Госавтоинспекции

The article is devoted to the analysis and description of technology of simulation of professional situations for testing the evaluation of the tactical and psychological preparedness of employees dorozhno-patrol service of traffic police. The algorithm development simulated situations, which includes such stages as: 1) analyzing the statistics of traffic accidents and violations of traffic regulations; 2) analysis of typical behavioral responses of drivers and other road users; 3) determination of the basic tactical and psychological techniques that are modeled in role-playing situations and complicating the interaction; 4) selection of the model (base) behavioral responses of drivers; 5) assessment of the possibility of modeling and adaptation of driver behaviors. Examples of descriptions of the simulated situations. Cited in the article, the material can be used in the design and conduct of the competition on the tactical and psychological training of the personnel of the state traffic Inspectorate and the education of future employees of the traffic police.

Dynamic response analysis of buck driver for LED based on second‐order model

The voltage–current characteristics of high-power LED are different from the conventional power diodes. Generally, the linear model of LED is used in the controller design for LED drivers. A nonlinear model of LED based on the V–I characteristics of LB-W5SM from Osram opto semiconductors company is built. The nonlinear model of LED is a second-order model. The dynamic performance of buck driver with nonlinear model of high-power LED is analysed. The dynamic equations of the V–I characteristics are deduced with curve-fitting. The comparison simulations of proportional–integral-controlled buck drivers with linear model and nonlinear model are conducted. The dynamic response of the second-order model driver is faster than the linear model.

Toward the Development of Standards for Yellow Flashing Lights Used in Work Zones.

Flashing yellow warning lights are important for worker and driver safety in work zones. Current standards for these lights do not address whether and how they should be coordinated to provide course-way information to drivers navigating through work zones. A field study in which the intensities and flash patterns of warning lights along a simulated work zone were varied during daytime and nighttime, was conducted to assess drivers' responses to different configurations, leading to several conclusions. During the daytime, driver responses were relatively insensitive to warning light characteristics, although they preferred sequential and synchronized flash patterns over random, uncoordinated flashing. At nighttime, a temporal peak intensity of 25 cd with a sequential flash pattern was optimal for providing course-way information. A single initial warning light having a higher intensity may help drivers detect the work zone without creating unacceptable visual discomfort.

Eye Movements and Road Hazard Detection: Effects of Blur and Distractors.

To examine the effects of optical blur, auditory distractors, and age on eye movement patterns while performing a driving hazard perception test (HPT). Twenty young (mean age 27.1 ± 4.6 years) and 20 older (73.3 ± 5.7 years) drivers with normal vision completed a HPT in a repeated-measures counterbalanced design while their eye movements were recorded. Testing was performed under two visual (best-corrected vision and with +2.00DS blur) and two distractor (with and without auditory distraction) conditions. Participants were required to respond to road hazards appearing in the HPT videos of real-world driving scenes and their hazard response times were recorded. Blur and distractors each significantly delayed hazard response time by 0.42 and 0.76 s, respectively (p < 0.05). A significant interaction between age and distractors indicated that older drivers were more affected by distractors than young drivers (response with distractors delayed by 0.96 and 0.60 s, respectively). There were no other two- or three-way interaction effects on response time. With blur, for example, both groups fixated significantly longer on hazards before responding compared to best-corrected vision. In the presence of distractors, both groups exhibited delayed first fixation on the hazards and spent less time fixating on the hazards. There were also significant differences in eye movement characteristics between groups, where older drivers exhibited smaller saccades, delayed first fixation on hazards, and shorter fixation duration on hazards compared to the young drivers. Collectively, the findings of delayed hazard response times and alterations in eye movement patterns with blur and distractors provide further evidence that visual impairment and distractors are independently detrimental to driving safety given that delayed hazard response times are linked to increased crash risk.

Driver Performance in a Cooperative Adaptive Cruise Control String

Cooperative Adaptive Cruise Control (CACC) has been proposed as a method to increase highway capacity and possibly enhance safety. Two experiments were conducted in a driving simulator to verify that drivers with CACC would effectively monitor the system’s longitudinal control and override the system in the event that greater braking authority was needed than the system was designed to provide. In the first experiment, the emergency response of drivers with the CACC was compared with that of drivers who manually controlled following distance within a string of vehicles. The CACC group experienced markedly fewer crashes and had longer mean time-to-collision. The second experiment examined whether the CACC safety benefit was the result of the CACC system’s limited automatic braking authority, an auditory alarm, or both. The results suggest that both auto-braking and an auditory alarm are necessary to achieve a crash reduction benefit, although the alarm alone may promote less severe collisions.

The Influence of Driver Expectation when Recognizing Lighted Targets at Nighttime

Over the years, in a night time driving scenario, expectancy has been linked with faster night time recognition. This study tries to evaluate the ability of observers to identify illuminated objects on the road in the absence of an associative pattern. In this study 47 of 60 participants did not respond to a light source that was in the drivers’ travel lane ahead. Of those who did not respond to the light when directly ahead, 64% indicated that had seen it beforehand. When the light was 2 meters to the drivers’ right, 33% that saw the light failed to respond. All of the drivers who saw the light before striking it claimed that they thought it was off the road until too late. When the drivers did not know what the light source was, they could not decipher where the light was. However, once aware of the presence of the light the average recognition distance improved 192 meters (632 feet) with 100% recognition. These results fit well with the SEEV search model and an Information Theory approach to driver expectancy. Previous claims that the difference between expected and unexpected driver responses is a 2 to 1 ratio was not supported by this research.

OPERATING SPEED OF VEHICLES DURING RAINFALL AT NIGHT: CASE STUDY IN PONTIAN, JOHOR

Speed is one of the important parameters of traffic flow that can be used to determine the performance of driver’s behaviour under various scenarios. Changes in weather conditions caused changes in drivers’ speed due to various reasons. In Malaysia, there is slightly high number of road accidents at night. Rainfall at night does not only cause poor visibility to drivers, but it also gives a sense of insecurity especially as there is a significant reduction in the visibility of the object in front. Improper road conditions can worsen the situation, for example, rainfall can cause water accumulation on road surfaces which can increase skidding problem, potholes and hydroplaning effect. In relation to these situations, hence it is crucial to understand how the abrupt situation affect response of driver’s in terms of the macroscopic behaviour. These unpredictable environmental changes seem like portraying a very unpleasant journey for drivers especially to travel under rainfall condition at night. Therefore, there is a need to observe how individual vehicles react in terms of speed adjustment and response to the different rainfall intensities downpour at night. Hence this study was conducted to determine the impact of different rainfall intensities at night on vehicles’ speed. Traffic data was obtained using automatic traffic counter at a cross section of a road at Pengkalan Raja, Pontian for about three months during monsoon season. Rainfall data report was obtained from the Department of Drainage and Irrigation, Pontian. From this study, it was found that there is a speed reduction from the dry condition regardless of rainfall intensities at night. As rainfall intensities at night higher, the speed reduction is higher as well except for heavy rainfall condition. The mean speed, 15th percentile and 85th percentile of vehicles decrease with the increase in rainfall intensity at night. It can be concluded that rainfall have impact on vehicle’s speed irrespective of their intensities. Findings from this study can be used to help local authorities and transport planners in planning an efficient traffic management system for a safer travel experience to road users in Malaysia.