Hierarchical Structure ofRoad AccidentsThehierarchical structure and the scenario of road accident is reviewed by roadaccident data, the database frameworkwithin which it is stored, using multilevel statistical models (K. Senthilkumar,2007). Anyanalysis of accident is mostly concerned with the causal factors linked withthe incidence of accident and mapping and modelling of the accidental scenariobased on those causal factors and finally drawing out of strategic measures forsafe traffic management.
Causes of Road TrafficaccidentsThemost basic question that arises out of any accidental scenario is the cause orthe reason of its production. The pattern of the combined picture of behavioural factors andassociated decision-making processes are generally accepted to be the main underlying causeof most motor vehicle collisions, injuries, and fatalities (Micheal, 2007). The use of excessive speedis the most significant factor in most motorvehicle collisions, injuries, and fatalities.
The average travelingspeed for motor vehicleshas increased significantly especially on major roads and freeways. This changecan be said to have occurred mainly from road network infrastructural anddesign improvements. At an excessive speed, there is no sufficient timefor the driver to stop the vehicle safely on any given road. Driving at speedsover the legal limit is a common behaviour of many drivers. One speedsurvey showed that just over half of drivers stayed below thedesignated 60 Km/hr speed limit (Zhang et al., 2000).
Theinstallation of fixed and mobile speed cameras has led to a significant decreasein road crashes both during day and nighttime, and also on roads with speed limits varying from 60 to 110 Km/hr(Christie et al., 2003).Drinkingand driving increases both the risk of a crash and the likelihood of death or a serious injury. The riskof involvement ina crash increase significantly above a blood alcohol concentration(BAC) of 0.
04 g/dl (Compton, 2002).Lawswhich establish lower BACs (between zero and 0.02 g/dl) for young/novice drivers can lead to reductions ofbetween 4% and 24% in the number of crashes involving young people (Shults, 2001).Enforcementof sobriety checkpoints and random breath-testing can lead to reductions in alcohol-related crashes of about20%, and has been shown to be very cost-effective (Elder, 2002).
Numerousstudies have demonstrated a positive correlation between blood alcohol concentration (BAC) and impairmentof motor coordination and cognitive performance, including the skilledperformance required to operate a motor vehicle (Voas et al., 2002).Inthe recent past, the role played by psychoactive substances in road safety has interesting subject. The frequent use andmisuse of these substancesalong with its associated behavioural risk cannot be ignored in perspective to reduce thehigh costs related to road accidents. Many reports have showed a growing andworldwide presence of psychoactive substances in drivers involved in road accidents (Kelly et al., 2004).
Cannabisimpairs the skills important for driving, including tracking, psychomotor skills, reaction time and performanceespecially in the first 2 hours after smoking. The main effect of marijuana wasto increase lateral movement of the vehicle moderately within thedriving lane on a highway (Berghaus et al., 2005). Surveys conducted in widely separated localitieshave generally revealedthe presence of tetra hydro cannabinol (THC) in between 4 and 14% of drivers whosustained injury or death in traffic accidents (Drummer et al.
, 2003). Studies have shown that alcohol and thecombination of alcohol with cannabissignificantly and strongly elevated crash culpability rates (Lowenstein et al., 2001).Infact, (an interesting fact to note), low to moderate acute doses of cocaine andamphetamine can beexpected to increase positive mood, energy, and alertness, especially in non-tolerantindividuals.
It seems likely thatabrupt discontinuation of eitherdrug in a chronic user could result in driving impairment (Bernhoftet al., 2003). The use of marijuana (THC), cocaine, opiates canreduce driving performance(Moviget al., 2004).A significant number of ill effects, leading to impairmentof the driving skills such as blurred vision, slow visual accommodation,disorientation, and eyehand coordination can be associated with the use the tricyclic antidepressants (TCAs),e.g., amitriptyline. However, the most dangerous is the feeling of drowsinessand sedation after such use (Koelega, 1993).
Disabled psychomotor andcognitive performance along with sedation has been found to be a productioncharacteristic of almost all the all first-generation antihistamines (cold andallergy medications) as compared to the the second generation antihistamines whichare generally safe at therapeutic doses (Jayet al., 2000).Driver fatigue and drowsy driving covers aspectrum ranging from drivingwhile clearly tired, up to episodes of “micro-sleeping” and finallyto falling asleep at the wheel.Risk factors include lack of sleep, driving while intoxicated withalcohol or other drugs, long periods of driving without rest, sleepapnoea, and other medical disorders. The problem is common and widespread.
Ithas been estimated that more than one-third of the driving population admits to have “nodded off”for at least a moment while driving. Mostinstances tend to occur late at night, with only 9% happening between 6:00 and11:00 a.m., whereas 28% occurred from midnight to 6:00 a.
m. (Stutts et al., 2003) Typical motor vehicleincidents that are caused by drowsy driving are single-vehicle run-off-the-road crashes andrear-end collisions (Horstman et al., 2000).According to Van & Donald (2001), drivers today are facedwith many problems when drivingin congested and overcrowded cities, especially being overloaded by the vastamount of informationthat needs to be continuously processed. The types of information a typicalcity drivermay encounter and need to react upon are numerous and include traffic signs, trafficsignals, advertisements, horns, loud music from passing vehicles, vehicle changinglanes, pedestrians and much more. It has been estimated that approximately 25%of all crashes in the United States result from driver inattention ordistraction. Further the consequence of the interaction with the moderntechnology also cannot be ignored.
These technology-based distractions including mobilephones, e-mail and the Internet, radio, CD and DVD players, and routeguidance systems and all may have a detrimental effect on distracted performanceof the drivers. Decrease in the rate of usage of the motor vehicle has beenfound especially during weekends or at nights with an exceeded speed limit andalso when the passengers are boarded in the vehicles (Johnson, 2004). Association of a personalhands-free mobile telephone than a handheld mobile telephone or hands-freespeaker mobile telephone with asignificantly lower additional work load has been found while driving on a highway (Matthews, 2003). According to a study conducted by Clarke et al(2007), out of the 1106 recorded car drivers who got killed in road trafficcrashes in the year 2005 at Britain and Wales, 40% of the victims had no worn seat belts, with their averageage hanging between 17 to 29 years.
Another interesting fact that got noticedin the survey was the increase in the awareness of tying the seat bel increaseswith the age of beyond 30 years. In fact, avoidance in the usage of seat beltboth by the drivers and the vehicle occupants during night, thereby resultingdeath casualty in road accidents has also been found to be significantly higher(Broughton and Walter, 2007).