Human Factors in Driving Task: SafeDistance MaintenanceNameInstitution Table of Contents1 Task Description. 32 Collisions Associated with Safe Distance Driving.
43 Task Analysis- Keeping Safe Distance. 53.1 Sub-Tasks.
53.2 Required Information. 64 Human Factors and Potential Errors.
84.1 Vision. 84.2 Cognition. 94.3 Motor function.
95 Countermeasures. 105.1 Advisory Signs. 105.2 Road Chevrons. 115.
3 Intelligent Transport Systems. 116 Summary. 127 References. 14 Human Factors in Driving Task: SafeDistance Maintenance1 Task DescriptionWhile people engage in driving as a daily task, itinvolves complex processes of information processing and imposes heavycognitive demands due to its dynamic nature. The dynamism occurs due to thechange in environmental conditions with which the driver must contend in thecourse of their activity, as well as the variations in their internal natureduring specific task performances. One of the most seemingly simple tasks indriving is the maintenance of safe distance between one vehicle and that ahead ofit. However, indications have been that drivers often fail in the execution ofthis task due to factors on the road or those emanating from their human nature (Mazureck & Hattem, 2006). Drivers in many cities have to contend with matters oftraffic jams, especially in the peak hours of the morning and in the evening.
The traffic often results in many drivers exhibiting tailgating, a practicewhereby the driver behind drives too closely to the driver in front (Song & Wang, 2012). Globalrecommendations for safe distance driving are of about 3 seconds, whereby 30meters is considered the equivalent of a second(Mazureck & Hattem, 2006). The rule changes depending on the roadconditions, increasing to four seconds in cases when the road is unclear due toconditions like fog, and ten seconds for roads tainted by snow (Mazureck & Hattem, 2006). Regardless,drivers will often overlook these recommended distances and especially withpressure from traffic. These driving tendencies have multiple motivators,including the perceptions of lateness and the illusion that the safe distance spaceis a waste of time, distractions, or even the desire to demonstrate subtleaggression while driving on the road (Song &Wang, 2012).
This paper focuses on analyzing the human factors thatpotentially interfere with the maintenance of safe driving distances.Understanding these factors is integral to understanding the possible way inwhich rear-end collisions may be mitigated on the highways. 2 Collisions Associatedwith Safe Distance DrivingSarkar et al (2000) classifies following a vehicle withinsufficient headway as a severe form of aggressive driving. According to the typical reaction time of adriver, the driver is advised to maintain a distance of more than two secondsbetween their vehicle and the vehicle ahead. Any performance of this task thatis within less time than this, depending on the speed of the moving vehicle, islikely to result in a road collision (Sarkar,Martineau, Emami, Khatib, & Wallace, 2000). This is an especiallyconsiderable challenge to road safety, considering statistics that indicateapproximately 18-20 percent of the global incidence in crashes involvedmultiple vehicles moving in the same direction not at an intersection (Mazureck & Hattem, 2006). The most common accident occurring from this type ofdriving task is rear end collisions.
According to data from the National Centerfor Statistics and Analysis (NCSA, 2010), rear end crashes accounted for morethan 30% of the 5.9 million accidents in the US between 2006 and 2008. Theseaccidents resulted in about 2200 fatalities and about 500,000 injuries annually (National Center for Statistics and Analysis, 2010).While tailgating is only accountable for about 70% of these automobilecollisions, the factor was also recorded as bearing the most prominentfatalities compared to the other rear end collision factor- inattention.
Assuch, safe driving distance is identified as a critical source of rear endcollisions for automobiles, especially in the USA. As the number of vehicles onthe road continues increasing and the periods when the roads encounter heavytraffic increase, the following distance for vehicles on the road becomes asignificant task to understand and consider in the design of highways. 3 Task Analysis- KeepingSafe DistanceMaintaining a safe distance between a vehicle and thevehicle ahead is a relatively uncomplicated task. Nevertheless, there areparticular actions in which the driver must engage in order to successfullymaintain its accomplishment. 3.1 Sub-Tasks2-3 second rule: the driver isexpected to maintain a consistent difference of between 2 and 3 seconds betweenthem and the vehicle that precedes them. This aspect requires deliberate visualscanning, whereby the use of stationary landmarks is effective. In this case,the driver should mark the point at which the previous vehicle passes alandmark, and between then and the moment when they pass the same landmarkthere should be a difference of about 3 seconds(Knipling, et al.
, 1993). It may be necessary, however, to increase thistime when the weather conditions are unfavorable to the degree of increasingthe required stopping distance (Knipling, etal., 1993).
Obstacles: the driver alsorequires to visually scan the road for potential obstacles both to theirdriving or the driving of the vehicle in front of them. Potential obstaclesinclude possible pedestrians, debris, or upcoming intersections that may forcethe driver in front to slow down (Adell,Várhelyi, & Dalla Fontana, 2011). In these cases, a change in speedfor the driver in front may compel and equal change in speed in order tomaintain the safe driving distance. Distracted drivers may lack the capacity toeffectively scan the environment, thereby failing to identify potentialobstacles that could end up decreasing their distance (Adell, Várhelyi, & Dalla Fontana, 2011). Consideration for vehicularcharacteristics: the characteristics of the vehicle in front of the driverare also crucial for their determination of the safe distance to maintain.
Vehicular characteristics could include heavy vehicles like lories, ordifferent forms of automobiles like motorbikes on the same roads (Knipling, et al., 1993). For heavy vehicles,the stopping distance tends to be lengthier. At the same time, some of the loriesare fitted with instant breaks, in which case these will often be indicated atthe back. Vehicular characteristics may also involve faults in the vehicleahead, such as break-lights that do not function. In the case of the latter,the driver must remain conscious enough to scan the break-lights of the vehicleahead of the immediate one, which they will use as a basis for adjustment ofspeeds and the maintenance of the safe distances(Song & Wang, 2012).
3.2 Required InformationThe performance of the specific sub-tasks by the drivertowards accomplishing safe distance maintenance relies on the access to a givenset of information. As with all driving tasks, the perception-reaction timecombines with the maneuver time to define the sight distance (Song & Wang, 2012). The capacity of thedriver to process information, therefore, determines their ability to completethe task or the specific sub-tasks efficiently. Meaning of road signs: Some ofthe critical information that the driver requires is the understanding of themeaning of road symbols. Drivers typically operate in an environment wherebysymbols are the most common forms of communication.
Under the assumption ofadequate visual capacity, the remaining components are of the understanding ofthe symbols they encounter along the road(Adell, Várhelyi, & Dalla Fontana, 2011). For instance, pedestriansigns will alert the driver of the possible change in road driving conditionssuch as speeds, and the implications these changes have on the current safedistance requirements. The driver also gains the need to look out forpedestrians as obstacles that could increase the possibility of a rear-endcollision where the safe distance is not maintained.
Driver behavior: the driver onthe highway also requires information on the behavior and condition of theother drivers on the road. Driver characteristics such as unnecessaryaggression or distraction could compromise the capacity of the rest of thedrivers for maintaining safe distances (Song& Wang, 2012). Information on the degree of driver attention of thevehicle ahead may compel the one behind to keep wider distances between them.At the same time, flashing taillights by the driver ahead may indicate a degreeof irritation or indications they feel the one behind is too close.
Consequently, the driver has the obligation to constantly assess this driverinformation, using it to monitor and negotiate consistently safedistances. Environmental or weather implications:additional information requires by the driver is on the current weather or theenvironment. Some weather conditions vary across regions, often changingabruptly, such as rain or hail or even sections of snowy roads. Driverinformation on the weather on the road is crucial, as sudden encounters ofweather changes will always compel a change in the required safe distancebetween the vehicles. Constantly monitoring for slippery roads will also guidechoices on when to vary the speed and the resulting implications on safe distance (Mazureck & Hattem, 2006).
Current speeds: driving onmultiple types of roads tends to have different characteristics, especiallywhere the speeds are concerned. Drivers on highways may be driving at higherspeeds than on smaller scale roads, which determines the perception of safedistances that drivers should possess (NationalCenter for Statistics and Analysis, 2010). Understanding the currentspeed enables the driver to make mental computations of the total stoppingdistance and, consequently, the required safe distance between them (Knipling, et al., 1993). Indications havebeen that driving at high speeds requires more reaction times from the driverseven where the perception time may not change.
For instance, while the averagereaction time is only about 0.75 seconds, the reaction time at 80mPh is about1.5 seconds (Knipling, et al.
, 1993).Awareness of the current speed of the vehicles on the road, therefore, iscritical information to guide the determination of the safe distance betweenthe vehicle and the one ahead. 4 Human Factors andPotential ErrorsDriver actions may be subject to errors, which willoften either have severe consequences or near-miss reports. According to theIndiana Tri-State Level study, indications were that human factors account forabout 93% of road driving errors, with environmental and vehicular factors onlyinfluencing about 34% and 13% of these incidences respectively (Treat, Tumbas, & McDonald, 1979). Consideringthe factors in their individuality, without cause overlap, human factorsaccount for about 57% of errors resulting on road accidents (Treat, Tumbas, & McDonald, 1979). Humanfactors are divided into cognition, vision, and motor function. Theirexpression determines the perception, decision-making, and reaction time thatthe driver exhibits.
4.1 VisionMultiple aspects connected to vision may impair thecapacity of the driver to maintain safe driving distance. Evidence indicatesthat errors in the distance maintenance emanate from problems emanating fromvisual processing of dynamic information (Song& Wang, 2012). For instance, the capacity of the driver to assesscentral movement in depth- as in the judgment of vehicles slowing ahead- maycompromise their ability to maintain safe distances. The visual acuity of thedriver may also be compromised, making it difficult for them to read road signswhile they are in motion (American Associationof State Highway and Transportation Officials, 2010). The result is thatthe driver ends up changing speeds later than they should have, severelycompromising the distance between the vehicles.
4.2 CognitionAnother cause for errors in the performance ofmaintaining safe distance is the range of cognitive influences. Cognition, inthis context, may vary to include inattention and divided attention, vigilance,and memory (American Association of StateHighway and Transportation Officials, 2010).
Divided attention impliesthe driver is monitoring multiple tasks at the same time, such as eating whilealso driving. While eating may be a trivial task, evidence has indicated thatsuch task ranges tend to interfere with the driving activity by about 350milliseconds (Levy, Pashler, & Boer, 2006).Consequently, where a driver is engaged in eating while driving, they may failto slow down in time to maintain the safe distance when the vehicle in front ofthem breaks, even if not suddenly. At the same time, vigilance and memory are criticalcognitive factors that determine the occurrence of errors in maintaining safedistances. Where a driver has been on the road for some time, the attentionthey devote to the driving task is limited(Fuller, 2005). This driver may be drowsy and fail to notice when theycome too close to the vehicle in front of them. Memory, long term and shortterm, also acts as a basis for error.
Drivers in familiar routes can anticipatefeatures such as road maps, and where they fail to remember the breaking ofvehicles in front of them may cause their compromising the safe distance (Fuller, 2005). 4.3 Motor functionErrors in maintaining safe distance may also occur dueto compromised motor skills. Common evidence indicates that motor skills becomecompromised with age, diminishing the simple reaction time for an individual (Dewar, Olson, & Alexander, 2007).
Therefore,where an elderly driver is required to adjust their speed in response to anunexpected event in order to keep the safe distance, they will often fail toaccomplish this task due to slower motor reflexes. The result will often be,even if only momentarily, the driver ending up tail-gating the vehicles infront or even causing a collision. 5 CountermeasuresThe errors occurring on the road regarding maintainingsafe distance emanate from relying on the judgment of the drivers to determinethe adequacy of the headway. However, there are specific engineering and roadconstruction solutions that could avert or diminish the occurrence of theseerrors and the resulting incidents of collision. 5.1 Advisory SignsOne of the possible countermeasures is the installationof advisory signs that either warn or advise against tailgating. The signs actas reminders of the proper distance to maintain, reducing the incidence ofdeviation among drivers. In a 1983 study at Ascot, Berkshire, the installationof an automatic warning sign helped reduce the incidence of drivers using the1-second gap by about a third (Helliar-Symons,Wheeler, & Scott, 1984).
The sign was automatically triggered whenvehicles at the location had a less than 0.7 second gap, but over time this gapwas raised to between 1 second and 2 seconds(Hutchinson, 2008). Alternative interventions have also included amechanical and permanent sign, which reminds the drivers to avoid tailgating.This sign as applied in Tennessee, Memphis, involved a hand-held indicationadvising against tailgating. It yielded an increase in compliance by 13 percent (Hutchinson, 2008). Therefore, drivers thatwould otherwise be distracted, such as one that is eating while driving, willbe forced to consciously perceive the expected modification in the safedistance.
5.2 Road ChevronsAnother counter measure applicable in the situation isthe presence of dots or chevrons on the road surface. These chevrons areinstalled at regular intervals, reflecting the ideal distance between vehiclesat average speeds on the given road. Under the assumption of vehiclestravelling at 60 miles per hour, and dots spaced about 80 feet apart, it willbe possible for drivers to generate mental patterns for maintaining adequateheadway. In this instance, the requirement would be that while each driver ison a given chevron, they can see two more between them to imply 180 feet apart.Consequently, considering the speed, the headway would be about 1.8 seconds (Hutchinson, 2008). Studies have supported the use of the dots or chevronsas a countermeasure to road errors emanating from safe distance challenges.
Thetrial of the same on UK and French motorways successfully managed to improvethe understanding of drivers on the correct headway that vehicles shouldmaintain (Hutchinson, 2008). On the otherhand, there have been disputes regarding the challenges that chevrons couldimpose. In some instances, they may act as distractions to the drivers. Inother cases their permanency hinders the flexibility that should accompany changesin speed and the resulting variation in headway(Song & Wang, 2012).
Regardless, where these challenges areoverlooked, the dots or chevrons do facilitate proper measurement of theheadway for vehicles. 5.3 Intelligent TransportSystemsHutchison (2008) proposes the use of intelligenttransport systems as approaches to countering the errors of tailgating bydrivers that are unaware.
These systems could include advanced collisionwarning systems as well as cruise control to act as cost effective measures againstrear-end collisions. Several trials have been implemented, such as theFollowing Distance Warning system, but these have yet to be introduced onto theroad (Hutchinson, 2008). Such systems areinstalled on the vehicle, allowing the driver behind to receive warnings whenthey drive too close to the vehicle in front. However, the transfer of such systems to actualapplication may prove difficult.
For instance, the drivers may be irritated bythe multiple warnings especially where their behavior is considered normal.Distances they may have perceived as safe may be highlighted as tailgating,which could influence the cognitive processes of other drivers on the road (Song & Wang, 2012). At the same time, thedrivers of the vehicle behind may lack the knowledge to properly interpretwarnings by the vehicle that is fitted with the system. However, as it is stillan idea in progress, these shortcomings may be overcome by future developments. 6 SummaryDrivers have to maintain safe distances between them andvehicles in front. However, relying on the judgment of the drivers oftenresults in tailgating, with the influence of traffic conditions causingcompromised distances. Tailgating has been the basis for many rear-endcollisions, a serious outcome considering the magnitude of these collisionsboth in the USA and globally.
Consequently, understanding the events andinformation necessary to maintain proper headway is critical for all drivers.These forms of information involve details on vehicle speeds, the weather, andthe conditions of vehicles on the road as well as those of other drivers. Regardless, the capacity for human factors to induceerrors in the maintenance of safe distances as a driving task is high.Indications are that the vision of the driver, their cognitive state, and theirmotor skills are critical determinants of efficiency.
As such, distractionssuch as eating while driving will cause distance reductions and poor vision mayresult in limited judgment on the proper distance to maintain. Particularengineering countermeasures emerge in the form of advisory signs, the use ofmeasurement chevrons, and intelligent driving systems. Advisory signs may beautomated to alert specific drivers of compromised headway, or manual to act asreminders for drivers in traffic. On the other hand, chevrons allow measuringdistance objectively by the individual drivers. The presence of intelligentdriving systems will have the vehicle ahead issue warning signs when the driverbehind comes too close.
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