1. AASHTO Green Book defined brakingreaction time as the interval from the instant that the driver recognizes theexistence of an obstacle on the roadway ahead that necessitates braking untilthe instant that the driver actually applies the brakes (AASHTO, 2011).An indicator of the driverspeed to implement a task following a mental processing is brake reaction time.”It includes the following components the visual perception time, mentalprocessing time, leg movement time and the device response time”. Many factorsaffect brake reaction time like age, gender, mental fatigue, alcohol intake,sleep deprivation, etc. “It is also affected by the features of the distractingstimuli, like the size of the object, color of the object, amount ofillumination in the background etc.” ( Ashok, et al.
, 2016).Table 1 shows that studies thathave been done obtained different results of brake reaction time values. Thestudies used different criteria for finding the value of brake reaction time;for example, in 1936, Green Shield used laboratory automobile as the studycriteria, while Sivak et al. (1981) used response to brake light as the studycriteria (McGee, et al.).
Table 1: Summary ofstudies on brake-reaction time (McGee, et al.) 2. Aim of the Study The aim of this paper is to studyall of the factors that affect the driver brake reaction time and mention somestudies that have been done as literature reviews.3. Brake Reaction Time for Sight Distances The driver characteristicperception-reaction time is considered an important factor in a variety ofhighway design and operations standards. One of the driver characteristics is sightdistance, which is the length of roadway that a driver can see ahead at anyparticular time.
There are three types of sight distances: stopping sightdistance (SSD), passing sight distance (PSD), and decision sight distance (DSD)(AASHTO, 2011).SSD is the sum of two distances(AASHTO Green Book, 2011):1) The distance traversed by thevehicle from the instant the driver sights an object necessitating a stop tothe instant the brakes are applied, and 2) The distance needed to stop thevehicle from the instant brake application begins. These are referred to as brakereaction distance and braking distance, respectively.
+ Where: :design speed, km/hr :Perception – reaction time, sec (AASHTO recommends 2.5 sec. as t) Decelerationrate, m/s2 : Grade, m/mPSD is the minimum sight distancerequired on a two-lane two way highway that will permit a driver to (AASHTOGreen Book, 2011):· Complete a passing maneuver without collidingwith an oncoming vehicle.· Complete a passing maneuver without cuttingoff the passed vehicle.
Passing sight Distance Formula:Figure1 shows the typical diagram of PSD maneuver that includes three distances asfollows:PSD = d1 + d2 +d3 Figure 1: Typical diagramof PSD (Bindra)As shown in the figure, the PSDcan be obtained by adding the three distances that are calculated from someother parameters as defined in the following: · d1 = Distance travelled by thevehicle P from its position P1 during the time in which vehicle P decideswhether or not, he should take over the slow moving vehicle S.· d2 = Distance travelled by thevehicle at P1 to its position at P2.· d3 = Distance travelled by vehicleR from position R1 to R2.· V = Design speed of the road in kph.
· m = Difference in speed of fast and slowmoving vehicles · a =Rate of acceleration in m/sec2 ofvehicle P.· t = Time required to complete the actualovertaking maneuver · s = Headway i.e. speed of the vehicles justbefore and just after the overtaking operation. The rate of acceleration (a) isbased on the speed of the vehicles as shown in Table 2 belowTable 2: Acceleration ratefor design speed (Bindra) Speed (km/hr) Acceleration rate (km/hr. sec) 25 5 30 4.80 40 4.45 50 4 65 3.
28 80 2.56 100 1.92 Thespeed of overtaken vehicle or slow moving vehicles (V-m) is considered asuniform all long. d1= 0.56 (V-m)d2 = 2s + 0.28 (V-m)*TTdepends on the speed of overtaking vehicle; therefore d2 can becalculated as:d2= b + 2*sd2= 0.
28*(V-m)*T + *a*T2 Where,a is in m/s2Therefore:d2= 0.28*(V-m)*T + andb =0.28*(V-m)*T 2s= or s =0.20*(V-m) + 6.0T = Ifa is in kph /sec thenT = Vb=V-md2= 2s + 0.
28* Vb*Td3= 0.28*V*T When the road is unidirectional and there is no interferencesof the opposite traffic, then d3 becomes zero, andtherefore;PSD= d1+ d2The passing sight distance for two-directional road is asfollows:PSD= d1+ d2 + d3PSD=0.56*(V-m) + 2*0.2*(V-m) +6.
0 + 0.28*(V-m)*T + 0.28*V*T Assumptions of PSD 1.
The passing or opposing vehiclestravel at the same speed that represents the design speed of the road.2. The speed of the vehicle beingpassed (impeder) does not vary during the passing maneuver and it is less thanthat of the passing vehicle by 19.2 km/h.3. The passing vehicle is capable ofaccelerating to the passing speed (19.2 km/h higher than that of the vehiclebeing passed) within a distance of about 40 percent of the distance coveredduring the passing maneuver.4.
The lengths of the vehicle beingpassed and that of the passing vehicle are that for the passenger car design vehicle(i.e., 5.7 m).5. The perception-reaction time ofthe driver of the passing vehicle is 1.0 sec for aborting the pass.
6. The same acceleration rate of 3.41m/s² used for developing stopping sight distances is used foraborting a passing maneuver.7.
Time headway of 1 sec existsbetween the passing and impeder vehicles at the end of an aborted or completedpass.8. At the point where the passingvehicle returns to its normal lane, the time headway between the passing andimpeder vehicles is 1 sec.Despite the formulas for findingpassing sight distance as mentioned before, AASHTO Green book, 2011 showed thepassing sight distances for different design speeds as shown in Table 3.
Thepassing sights distance values are based on the researches that have been verifiedwith field observation of passing maneuvers (AASHTO Green Book, 2011).Table 3: Passing sightdistance for design of two-lane highways (AASHTO, 2011) DSD is the distance needed for adriver to detect an unexpected or otherwise difficult-to-perceive information source orcondition in a roadway environment that may be visually cluttered,recognize the condition or itspotential threat, select an appropriate speed and path, and initiate and completecomplex maneuvers (AASHTO, 2011). Because decision sight distanceoffers drivers additional margin for error and affords them sufficient lengthto maneuver their vehicles at the same or reduced speed, rather than to just stop,its values are substantially greater than stopping sight distance (AASHTO, 2011).The decision sight distances,which are shown in Table 4, may be used to:1) Provide values for sight distancesthat may be appropriate at critical locations, and 2) Serve as criteria in evaluatingthe suitability of the available sight distances at these locations. Table 4: Decision sightdistance (AASHTO, 2011) Where; : design speed, km/hr : Perception – reaction time, sec Deceleration rate, m/s2 : Grade, m/mAs indicated in the three sightdistances mentioned before, the perception-reaction time for each type of thesight distances are different; they can be summarized in Table 5. Table5: Brake perception reaction time for the threetypes of sight distances (AASHTO, 2011) Type of Sight Distance Brake Reaction Time Value, sec Description SSD 2.5 – PSD 1 – DSD 3 Avoidance maneuver A: Stop on rural road 9.
1 Avoidance maneuver B: Stop on urban road 10.2 -11.2 Avoidance maneuver C: Speed /path/direction change on rural road 12.1 -12.
9 Avoidance maneuver D: Speed /path/direction change on suburban road 14.0 -14.5 Avoidance maneuver E: Speed /path/direction change on urban road 4. Effect of Brake Reaction Time on Safety Driver reaction time is one of themost important measurement components in crash avoidance research ( Sena, et al., 2016).
When road accidents are beingreconstructed the accident reconstruction experts are almost without exceptionconfronted with the determination of driver’s reaction time. Regarding trafficsafety, the driver’s reaction time is the time which runs from the moment ofdriver’s perception of danger to the moment of driver’s reaction to thecircumstances either by steering or braking (T. Magister, 2006). Increases in reaction time canlead to safety risks on the road. In situations such as the braking response,the reaction time of the driver is not simply only one step process, but rathera sequence of complex reactions ( Anderson, et al., 2012).5.
Literature Review This literature covers severalstudies about the factors that affect brake reaction time such as gender, age,mental fatigue, alcohol intake, sleep deprivation, and so on. 5.1 Effects of Gender onBrake Reaction Time In 2016, J.
Ashok, V. Suganthi,and I. Vijayalakshmi conducted a study to assess the effect of gender on brakereaction time. The study was done in and around the Veerapandi village in Salemdistrict, Tamilnadu. They selected 35 male and 25 female drivers whose ageswere between 25 and 35 years and they had been in good health. The study wasdone by using a stationary car that was connected to a computer. They used SPSSstatistical software for data analyses.
They used a change in the color oflight as the stimulus that presented for the braking response. They obtainedthat the males responded faster for the visual stimuli than for auditorystimuli. Males responded quicker to unexpected stimuli in the experimentalcondition than females. As a conclusion, they obtained that brake reactiontimes for males are shorter than that for females as shown in Table 6.Table 6: Mean ± SD ofBrake Reaction Time in male and female drivers ( Ashok, et al.
, 2016) As shown in the table, the meanvalue of braking reaction time for the females was 0.863, which was greaterthan braking reaction time for males, which was 0.640 seconds.
They showed thanthere is a significant difference between them because the p-value was 0.0007,which was much lesser than 0.05. 5.2 Effect of Age on BrakeReaction Time In 2012, Brown conducted a masterstudy entitled “A Comparison of Drivers’ Braking Responses across Ages”. Thestudy had two independent variables: age, and test type (complex drivingsimulator, simple floor model tester, or simple driving simulator test).
Itincluded two dependent variables: time as measured by seconds and force asmeasured by pounds. They concluded that Older drivers’ complex braking reactiontimes had greater variability and increased time from their simple reactiontimes than did those of the younger participants as shown in Table 7. Table 7: Brake ReactionTime (Danielle, 2012) 5.3 Effect of MentalFatigue on Brake Reaction Time Driving fatigue is a commonphenomenon during driving, and is a hot research topic in the field.
Fatigue has a remarkable impact on a driver’sperceptions, attention, decision-making and judgement. The control ability of avehicle is directly determined by a driver’s reaction ability during drivingperformance ( Guo, et al., 2016). Guo et al. conducted a research aboutrelationship between reaction ability and mental state for online assessment ofdriving fatigue. The relationship between driving fatigue, physiologicalsignals and driver’s reaction time was analyzed.
Twenty subjects were tested duringdriving. All the subjects who held a driving license were screened foreligibility. Twelve males (60%) and eight females (40%) were voluntarilyrecruited for this research from the general public. Their ages ranged from 24to 51, and their driving experience ranged from three years to 25 years. It wasensured that the subjects had sufficient sleep, with no alcohol or coffee for24 hours prior to participation in the experiments.
In the experiment asimulator, a biopac system, a reaction time test system and a computer wasused. Grey correlation analysis was used to select the input variable of theclassification model. A support vector machine was usedto divide the mental state into three levels.The three levels (self-assessmentmethod) were proposed based on Stanford Sleepiness scale in order to allow thedriver to also perform a self-assessment quickly and intimately. Level 1represented the drivers in a state of vigilance. Level 2 represented the driverswith slight mental fatigue.
Level 3 represented the drivers with serious mentalfatigue. The detailed scale statements of the levels is shown in Table 8 below Table 8: Self-assessmentscale ( Guo, et al., 2016) The study also regarded age andgender of drivers for different mental levels. As shown in Figure 2, Level 1had lower reaction time as indicated by the black data line; Level 3 (red dataline) had the greatest reaction time, while the reaction time in Level 2 (bluedata line) was in between them. Figure 2: The relationship betweenreaction time, age, gender and mental fatigue levels( Guo, et al., 2016) On the other hand, the study obtaineddifferent results of braking time for different mentality fatigue regardinggender of drivers as shown in Table 9. Table 9: The averagereaction time of different mental level ( Guo, et al., 2016) As indicated in the table, it isclear that Level 3 had the largest average reaction time, while Level 1 had thelowest average reaction time, which indicates that the reaction time becomeslonger as mental fatigue accumulates.
The study concluded that femaleshad a longer reaction time than males when driving fatigue accumulated. Thestamina of females was poorer than males, which indicates that females may getfatigued faster than males. Moreover, there was a difference between males andfemales for the same mental level. The reaction time of females had been foundto be longer than males for each mental level. The higher the mental level, thebigger the gap between males and females.
They also considered the age ofdrivers as is another significant factor that can influence the reaction time.The results of the average reaction time of different age groups are shown inTable 10.Table 10: The averagereaction time of different age groups ( Guo, et al.
, 2016) The age of drivers were dividedinto two groups: age 20–30 years, and over 30 years. This type of driver mayhave a long reaction time. As a result of the study, theyconcluded that females have a faster decrease in reaction ability than males whendriving fatigue accumulates. Elderly drivers had longer reaction times than theyoung drivers.Talusan, et al.,(2014) investigated the difference inbrake reaction times of night float and post-call physicians in training. Inthis study conversion of a night float schedule for overnight coverage wasassessed.
Participants were trainees in their first to fourth years of trainingat Yale- New Haven Hospital. Only physicians in training who had driven a carin previous six months were allowed to be participants. Exclusion criteria wereincluded not driving cars regularly or injuries to the lower extremities(sprain, fracture, other lower extremity pain). Participants were in internalmedicine and orthopaedic surgery filled out a survey that involved the EpworthSleepiness Scale (a subjective measure of a participant’s sleepiness), theirage, year in residency, and specialty.
Between 7 am and 9 am the participantswere again approached for post-shift survey and reaction time testing. Driving simulatorwas used to record brake reaction time. Several groups of interest wereestablished as variables: all interns, all residents, orthopedic interns andresidents, internal medicine interns and residents, night float shiftparticipant and those on traditional 28-hour call shifts. As a statisticalcriterion, a paired sample t-test was used to compare the reaction times.Wilcoxon signed rank test was conducted to compare results from the EpworthSleepiness Scale for each group. It was found that there is an overall increasein reaction times for post-call trainees compared to pre-call trainees.They obtained that after atraditional 28-hour call shift, trainees had significantly worse brake reactiontimes than they did prior to their shift, whereas traineeson night float rotations had non-significant increases in brake reaction timespost-shift. Both groups had higher post-shift scores on the Epworth SleepinessScale, which suggests that participants in each group were sleepier post-shift,despite the fact that the night float group had no significant difference inbrake reaction times.
5.4 Effectof Alcohol Intake on Brake Reaction Time Christoforou in 2013 studiedthe influence of alcohol on reaction times for young impaired drivers. Thebehavior of young driver under the influence of alcohol was explored by usingdriving simulator experiment. Forty nine participants were subjected to acommon pre-defined dose of alcohol consumption and the subjects underwent fivedifferent stages in the experiment. The study was conducted by using breathtest for knowing the level of drinking alcohol from drivers. The results of the breath of all independentvariables considered along the experiment with summary statistics weresummarized in Table 11. Table 11: Explanatoryvariables in reaction time analysis ( Christoforou, et al., 2013) According to the table, differentreaction times were obtained for different drinking levels from drivers.
Forexample, the reaction time was 1.2 seconds for BrAC1/3; while, the reactiontime was 0.3 second for BrAC-1. These different obtained values of the reactiontimes were based on time after alcohol ingestion from the drivers. Inthe analytic technique of the study, multiple linear regressions were used tomodel the relationship between a continuous dependent variable and severalregressors.
Several parameters relating to the drivers characteristics weremodeled, and named as model 1 type and model 2 types as shown in Tables 12 and13. Table 12: Model estimationresults for model type 1 ( Talusan, et al., 2014) Table 13: Model estimationresults for model type 2 ( Talusan, et al., 2014) 5 ConclusionThe results of this study shows that the braking reactiontime depends on several factors such as gender, age, mental fatigue, alcoholintake by drivers, etc. Despite the factors that affect the braking reactiontime, the braking reaction time is different based on the type of vehiclemaneuvers or sight distances such as SSD, DSD, and PSD. However the brakingreaction time is based on several factors as mentioned before, AASHTO recommend2.5 seconds for design of geometric elements based on SSD, 1 second for PSD,and greater different values for DSD.
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