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An Analysis on FARS Data Over a Period of 15 years (1998 to 2012)

An Analysis on FARS Data Over a Period of 15 years (1998 to 2012)(Traffic Safety Term Paper)GROUP Abhinav MishraAkash ChandraAnurag SinghalDileep LachhetaMayank AgarwalPrabhat K. RaviRocky Kasana IntroductionIn the current research alcohol consumption has been studied & for deep insight data has been divided into following categoriesBlood Alcohol ConcentrationData Type NameAll (irrespective of BAC)Type-I0.01g/dLto 0.94+g/dLType-II0.01g/dLto 0.08g/dLType-III0.08g/dL to 0.94g/dLType -IVParameters ConsideredAgeSexNumber of OccupantsRestraint System UsedCrash Time EthnicityRoadway Function ClassStatistical Analysis: Mann-Whitney Test

What is it for? A non-parametric test to compare the central tendencies of two groupsIt assumes Random assignments to groupsTest statistic: UBased on ranks from two independent samples, they correspond to the t test for two independent samples, except that no assumptionsare necessary regarding normality ore equality or variancesMann-Whitney Test: Procedure

Rank all scores together, ignoring which group they belong Separately sum the ranks for the first and second samplesSelect the larger of these two rank totals, and call it TX

SampleNull hypothesisThe two groupsare the same Null distributionU (Ustatic with n1, n2) compareHow unusual is this test statistic?P < 0.05P > 0.05Reject HoFail to reject HoMann-Whitney U testTest statisticU1 or U2

Mann-Whitney U test

Critical Values for 1 and 2 Tail Tests2 Tail Confidence.1 Tail ConfidenceUCriticalU < U Critical80.0%90.00%200YES90.0%95.00%192YES95.0%97.50%184YES99.0%99.50%171YESAssume Ustatic=120AgeFARS data is divided into different age groups namelyunder 2020 to 29 years30 to 39 years40 to 49 years50 to 59 years60 years and above

Type-IIIType-IVPercentage Change Year-wiseVariations in fatality with age for data Type I & IIObservations (Type 1 & Type II)Younger persons are more involved in crashes in comparison to older personsIn Type-II data, number of fatalities are more for person with age between 20 & 29. This may be due to 21 year minimum drinking age lawIn both cases there is decrease in fatalities after 2007 which may be due to change in enforcement. For type-I data, graph shows that there is decrease in fatalities with persons involving age less than 20 after 2004 while there is increase in crashes with person age group between 20 & 29.

Variations in fatality with age for data type III & IV

Observations (Type III & Type IV)In both cases persons in age group of 20-29 are much more involved in crashes in comparison to any other age groupFatalities for each age group face a sharp decrease after 2007 which may be result of certain measures of enforcement.Fatalities involving persons with BAC within limit are not changing much with time but have decreased by a small value after 2007Number of OccupantIn order to see the variation for different types of vehicles the data has been divided into following groupsOneTwoThree to sixMore than six

Variations in fatality with number of occupant for data type I & II15Observations (Type 1 & Type II)Numbers of fatalities are not changing much after 2010 in all crashes specifically in alcohol related crashes.People are less likely to drink when they travel in group of six and more (may be public vehicle!)Number of fatalities with number of occupants 1 are very high in comparison to fatalities with number of occupants greater than one. It might be possible due to two reasons. Fraction of persons travelling alone is morePeople tend to drive more carelessly if they are travelling alone

Variations in fatality with number of occupant for data type IIII & IVObservations (Type III & Type IV)Fatalities are more for data type-IV as compared to data type-IIINumber of fatalities with number of occupants one are very high in comparison to fatalities with number of occupants greater than one. Numbers of fatalities are not changing much with time for crashes involving persons with BAC within limitAlthough numbers of fatalities are approximately same for people with BAC within limit and above limit visually but statistically they are different.GENDER VARIATIONHow many Males and Females actually drive on U.S. Roads?The percent of licensed drivers that are males declined with time from 52.4 percent in 1983 to 50.3 percent in 1997. It then leveled off because females had become 50 percent of the drivers. Presently almost equal numbers of male and female drivers are present on U.S. roads.

OBSERVED TRENDSAll fatalities vs fatalities under the influence of alcohol for both male and femaleOBSERVATIONSNumber of fatalities both among male and female had taken a significant plunge after 2006. Number of fatalities which were recorded under the influence of alcohol had remained almost same and had decreased only after 2010.

OBSERVATIONSMale drivers continue to surpass women in the number of alcohol-involved fatal crashesThat is why after enforcement of stricter laws a higher decrease is observed among the male gender after 2010.

OBSERVED TRENDSFatalities of drivers within the legal limit vs. beyond the legal limit of BAC for both male and female

OBSERVATIONSThe numbers of male driver fatalities that drive after drinking beyond the legal limit are considerable higher than the number of females.

OBSERVATIONSWith the increase in the blood alcohol concentration the number of fatalities in both male and female increases.There has been a considerable decrease in the number of male deaths after 2008

Factors responsible for this decreaseover the yearsEnforcement of Zero Tolerance laws that establish maximum legal BAC limit of .02 for those under 21 years of age while operating a motor vehicleLaws that provide for administrative license revocation or suspension prior to conviction for driving under the influenceLaws that set the minimum legal drinking age to 21 Laws that define a blood alcohol concentration above a specified threshold as sufficient evidence of driving under the influence

CRASH TIMEEntire period of 24 hours was divided the into four sub-segments:-00:00 AM to 05:59 AM06:00 AM to 11:59 AM12:00 PM to 05:59 PM06:00 PM to 11:59 PM

OBSERVED TRENDSAll fatalities vs. those under the influence of alcohol

Type IOBSERVATIONSInfluence of alcohol was recorded more in the 12 hour span of 6PM to 6AM than its other half. This points that people under the influence of alcohol are higher in number during the night time and they had more likelihood of getting involved in a crash.

OBSERVATIONSGeneral fatality trend points more deaths in the 12 hour span of 12PM to 12AM but the number of people dying due to alcohol involvement are still higher in 6PM to 6 AM span.For a particular year say 2009, overall on an average one alcohol-impaired-driving fatality has occurred every 48 minutes. However, these fatalities did not occur evenly throughout the day. In 2009, from midnight to 3 a.m., two-thirds of fatal crashes involved an alcohol-impaired driver which is twice the overall average.

OBSERVED TRENDSFatalities of drivers within the legal limit vs. beyond the legal limit of BAC

OBSERVATIONSNumber of fatalities of people drunk within the legal limit of BAC less than .08 were lesser and most of them were observed in the time group 6 PM to 12 AM. The percentage of alcohol-impaired drivers involved in fatal crashes by time of day also remains consistent from year to year.

OBSERVATIONSNHTSA (DOT HS 811 523)Time of Day and Demographic Perspective Of FatalAlcohol-Impaired-Driving Crashes

This behaviour was consistent with our analysis for all the years.

Restraint System UsedAnalysis under this category is carried out considering the usage of Restraint SystemRestraint System UsedRestraint System Not-UsedRestraint System Improperly Used

Variations of fatalities with restraint system use for data Type-I & IIObservations (Type 1 & Type II)For type I case, there were less fatalities when restraint system was not used as compared to the fatalities when restraint system was used.Whereas in Type II case, the trend is opposite.So, use of restraint system played a major role in reducing fatalities in alcohol related cases.For both types I and II, the number of fatalities reduced with time specifically in the case when restraint system was not used.This is possibly because restraint system use didnt play a major role as compared to other factors like enforcement laws, increased awareness of people etc.In recent years (since 2010), the number of fatalities has not changed much.Variations of fatalities with restraint system use for data Type-III & IVObservations (Type III & Type IV)For Type III case, there is considerable difference between the number of fatalities when restraint system was used and when that was not used. However, there is not much difference between the number of fatalities when restraint system was used and when that was not used in Type IV case.The number of fatalities has slightly increased over time when restraint system was used.The reason for this observation might be that people who had taken alcohol were less concerned with traffic safety when they have used restraint system.

Roadway Function ClassFor analysis in present study, this is divided into following categoriesRural InterstateRural OthersUrban Interstate Urban OthersVariations in fatality with roadway-function class for data type III& IVObservationsFor both the cases Types III and IV, fatalities on rural roadways were more than fatalities on urban roadways. Number of fatalities occurred on interstates roadways was lesser than that in other roadways due to better infrastructure and traffic safety measures pr