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The safest seat: Effect of seating position on occupant mortality
Journal of Safety Research 39 (2008) 433 – 436 www.elsevier.com/locate/jsr
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The safest seat: Effect of seating position on occupant mortality James Mayrose ⁎, Aruna Priya Buffalo State College, Mechanical Engineering Technology, 1300 Elmwood Avenue, Buffalo, NY 14222 State University of New York at Buffalo, Department of Emergency Medicine, Buffalo, NY 14215 Available online 5 August 2008
Abstract Introduction: This study investigated the survival rates of occupants of passenger cars involved in a fatal crash between 2000 and 2003. Methods: The information from every fatal crash in the United States between 2000 and 2003 was analyzed. Variables such as seat position, point of impact, rollover, restraint use, vehicle type, vehicle weight, occupant age, and injury severity were extracted from the Fatality Analysis Reporting System (FARS). Univariate and a full logistic multivariate model analyses were performed. Results: The data show that the rear middle seat is safer than any other occupant position when involved in a fatal crash. Overall, the rear (2nd row) seating positions have a 29.1% (Univariate Analysis, p b .0001, OR 1.29, 95% CI 1.22 - 1.37) increased odds of survival over the first row seating positions and the rear middle seat has a 25% (Univariate Analysis, p b .0001, OR 1.25, 95% CI 1.17 - 1.34) increased odds of survival over the other rear seat positions. After correcting for potential confounders, occupants of the rear middle seat have a 13% (Logistic Regression, p b .001, 95% CI 1.02 - 1.26) increased chance of survival when involved in a crash with a fatality than occupants in other rear seats. Conclusion: This study has shown that the safest position for any occupant involved in a motor-vehicle crash is the rear middle seat. Impact on Industry: The results of this research may impact how automobile manufacturers look at future rear middle seat designs. If the rear seat was to be designed exactly like its outboard counterparts (headrest, armrests, lap and shoulder belt, etc.) people may choose to sit on it more often rather than waiting to use it out of necessity due to multiple rear seat occupants. © 2008 National Safety Council and Elsevier Ltd. All rights reserved. Keywords: Seating Position; Fatality; Crash; Safety
1. Introduction There were 42,643 traffic fatalities in the United States in 2003. Of those, 31,905 (75%) were occupants of passenger vehicles (cars, light trucks, vans, and SUV's). Of the 29,381 (92%) occupants for which restraint use was known, 16,593 (56%) were unrestrained at the time of the crash. Of these 29,381 occupants, 2,662 were rear seat occupants, 1,680 (68%) of which were unrestrained (National Highway Traffic Safety Administration [NHTSA], 2003). It is well known and widely accepted that the proper use of restraint systems saves lives and reduces the extent and number of injuries sustained by occupants involved in a motor-vehicle crash. There is also additional evidence in the literature documenting the reduced risk of injury and fatality to rear seat passengers as compared to front seat occupants. ⁎ Corresponding author. Tel.: +1 716 878 4802; fax: +1 716 878 3033. E-mail address: [email protected] (J. Mayrose).
A number of studies in the literature have also investigated the association of passenger seat position with the risk of death and serious injury when involved in a crash. One such study estimates that occupants in the rear seat of a passenger vehicle involved in a crash have a 39% reduced risk of death as compared to their front seat counterparts (Smith & Cummings, 2004). Another study documents an 18% decrease in fatalities for rear seat occupants wearing lap belts (Evans & Frick, 1988). Three point restraint systems and age appropriate safety systems have also been shown to provide even greater protection than lap belt only systems for rear seat occupants (Johnson & Falci, 1990; LeGay, Petrie, & Alexander, 1990). In regards to child safety, (Braver, Whitfield, & Ferguson, 1998) found that among children under 13 years of age, fatality risk was 38% lower for properly restrained rear seated children compared with those positioned in the front seat Braver et al. (1998). A more recent study by Winston et al. found children were 40% safer in the back seat than in the front when involved in a crash and that the risk of injury dropped to less than 2%
0022-4375/$ - see front matter © 2008 National Safety Council and Elsevier Ltd. All rights reserved. doi:10.1016/j.jsr.2008.06.003
434
J. Mayrose, A. Priya / Journal of Safety Research 39 (2008) 433–436
Table 1 Number of survivors by seat position and restraint use Seat Position No Restraint Used
Restraint Used
N
Front Seats
4,561
Rear Seats
7,512
Front Seats
8,332
Rear Seats
6,693
Table 2 Descriptive Data Occupant Position Subgroups
Survived (%)
Odds Ratio (95% CI)
p-value
2749 (60.3) 5306 (70.6) 7029 (84.4) 6087 (91.0)
1.585 (1.47 - 1.71)
P b.0001
1.862 (1.68 - 2.06)
p b .0001
when these rear seated children were harnessed in age appropriate restraint systems (Durbin, Chen, Smith, Elliott, & Winston, 2005). Although the literature suggests that the optimal seating location for passengers is the back seat of a vehicle and that children should use an age appropriate restraint system, it is unclear what the optimal location in the back seat is for properly restrained occupants of any age. In this study, we investigate the fatality rate of passengers seated in the rear middle seat versus those seated in other positions. 2. Methods A retrospective cohort study of fatal crash data concerning rear seat occupants involved in a fatal crash was obtained from the Fatality Analysis Reporting System (FARS), developed by the National Highway Traffic Safety Administration (NHTSA), for the years 2000 through 2003 (NHTSA, 2000-2003). Any vehicles with missing or unknown information regarding age, seat position, restraint use, injury severity, or vehicle type and weight were excluded from the study. A special class of crashes with a rear middle seat passenger was evaluated in order to compare the fatality rate of all rear seat occupants versus all front seat occupants. The numbers of fatalities in all of the front and rear seat occupant positions were compared. The information obtained from the FARS database with crashes involving rear seat occupants riding in a passenger vehicle was used to evaluate rear seat fatality risk. To assess whether the center rear seat is a safer seating position than either of the outboard rear seats, univariate analyses and multivariate logistic regression models were used. Chi-square analysis was used to test for statistical significance of the relationship between dichotomous variables. Odds ratios (OR) and confidence intervals were also calculated. Statistical significance was defined as p b 0.01. This study was approved by our Health Sciences Institutional Review Board.
Total Population N Occupant Age 0-4 5-8 9-16 N16 Restraint Use Yes No Injury Severity Lived Died
Outboard Seat
5707 (17.1%)
27611 (82.9%)
1631 (28.6%) 704 (12.3%) 1256 (22%) 2116 (37.1%)
4405 (16%) 2723 (9.9%) 6458 (23.4%) 14025 (50.7%)
2675 (46.9%) 3032 (53.1%)
15015 (54.4%) 12596 (45.6%)
4513 (79.1%) 1194 (20.9%)
20750 (75.2%) 6861 (24.8%)
passengers was 70.6% and 60.3% for unbelted front seat passengers. The survival rate was 91.0% for belted rear seat passengers and 84.4% for belted front seat passengers. Table 1 shows the lower fatality risk of the rear seating positions as well as the added protection seat belt use provides. The fatality rate for the rear middle seat position was then compared to both rear outboard seating positions. The FARS database included 34,470 rear seat occupants of passenger vehicles involved in fatal crashes that occurred over the 4 year study period. In this data set, we have complete records that met the study criteria on 33,318 (97%) occupants. The average age of the population was 20.09 years. Restraint use for the entire data set was 53.1% and the overall number of fatalities was 8,055 (24.2%). Rear seat passengers were placed in one of two groups based on their seating position at the time of the crash. The middle seat group contained 5,707 (17.1%) occupants, while the outboard seat group contained 27,611 (82.9%) occupants. The average age of the middle seat occupants was 15.45 years versus 21.05 for the outboard occupants. Table 2 shows the descriptive statistics for each of the two groups of occupants. Chi Square analysis comparing the two groups by injury severity (Lived or Died) and any restraint use (Yes or No) was performed. A statistically significant difference was found (p b .001) where middle seat occupants, whether restrained or unrestrained, had a higher rate of survival than outboard occupants (Table 3). The primary statistical tool used in the second step of the analysis was logistic regression where the outcome of the analysis was survival of the rear seat occupant involved in the crash. The primary variables of interest were seating position, principal impact point, rollover, restraint use, age, and body type. The results of this analysis show that occupants of the rear Table 3 Survival of belted versus unbelted occupants by seating position
3. Results There were 27,098 occupants of motor vehicles involved in a fatal crash between 2000 and 2003 where a rear middle seat passenger was present. The survival rate for unbelted rear seat
Middle Seat
Middle Seat
Restrained Unrestrained
Outboard Seat
Lived
Died
Lived
Died
2386 (89.2%) 2127 (70.2%)
289 (10.8%) 905 (29.8%)
12663 (84.3%) 8087 (64.2%)
2352 (15.7%) 4509 (35.8%)
J. Mayrose, A. Priya / Journal of Safety Research 39 (2008) 433–436 Table 4 Logistic Regression Model for Significant Variables (Survival) Odds Ratio Estimates for Rear Seat Occupants (Survival) Effect Middle Seat Rollover Restraint Use Impact Point Impact Point Body Type Body Type Age Group Age Group
Point 95% Wald Estimate Confidence Limits Middle seat vs. Any side seat No Rollover vs. Rollover Restraint Used vs. Not Used Front vs. Side Front vs. Rear Van/SUV vs. Cars Van/SUV vs. Pickup 0-4 years vs. above 16 years 5-15 years vs. above 16 years
1.133 1.491 2.801 2.205 2.274 1.817 1.175 1.276 1.558
1.015 1.318 2.637 2.045 2.065 1.551 1.036 1.171 1.458
1.264 1.687 2.976 2.376 2.504 2.129 1.331 1.391 1.664
middle seat are safer than those seated in either of the rear outboard positions. The estimated odds of survival for a rear middle seat occupant is 1.25 (Univariate Analysis, p b .0001, 95% CI 1.17-1.34,) times that for a rear seat outboard occupant. In addition, the estimated odds of survival for restrained rear seat occupants are 3.16 (95% CI 2.99-3.33, p b .0001) times that for unrestrained rear seat occupants. The data also show that rear seat occupants involved in a head-on crash have a higher probability of survival as opposed to any other point of impact (OR N 2, p b .0001). Age and vehicle type were also significant factors for estimating the survival of rear seat occupants. Children age 15 and younger are two times more likely to survive a crash than older rear seat occupants. Rear seat occupants of SUV's are 1.71 and 1.21 times more likely to survive a crash than rear seat occupants of passenger cars and pickup trucks, respectively. After testing the univariate models for all variables of interest, variables found to be significant along with their interaction variables were fit into a full logistic model that included all logical interaction terms. As is shown in Table 4, the odds of survival for occupants of the rear middle seat are 1.133 (95% CI 1.015 - 1.264) times higher than other rear seated occupants. Restrained rear seat occupants are also 2.801 (95% CI 2.637 - 2.976) times more likely to survive the crash than unrestrained rear seat passengers. The results of the odds estimates of survival coincide with the results obtained in the univariate analysis. All the variables of interest show a statistically significant effect on survival based on occupant position.
435
Although front seat belt use rates continue to climb year after year and have reached an all time high of 80% nationwide in 2004, rear seat occupants still have a very low restraint use rate as is seen from this data (NHTSA, 2005). In addition, belt use rates in crashes with a fatality tend to be lower than observed belt use rates in the total population (Mayrose et al., 2005). In this current study, nearly half (46.9%) of the 33,318 occupants riding in the rear seat were unrestrained. Of these unrestrained occupants, 34.6% were fatally injured in the crash while only 14.9% of restrained occupants were killed. The multivariate analysis for restraint use showed an odds estimate of 2.801 (p b .0001, 95% CI 2.637 - 2.976), which represents the likelihood a restrained rear seat passenger has of surviving a crash versus that of an unrestrained rear seat passenger. The analysis also revealed a number of other variables that have a significant effect on rear seat occupant survival when involved in a fatal crash. Body type, Impact Point, Rollover, age, restraint use, and seating position were all found to have a significant effect on survival. The data in this study shows a strong association between occupant seat position and survivability of a crash. Other studies have investigated the lower fatality risk of riding in the rear seat but only for selected samples of children without controlling for potential confounders (Evans & Frick, 1988; Braver, Whitfield, & Ferguson, 1998). 5. Limitations It has been shown in the literature that occupants of a crash restrained by only a lap belt suffer more extensive injuries compared with those occupants restrained with a lap/shoulder safety belt system. The extent of injuries to rear middle seat occupants due to the use of only a lap belt were not investigated in this study, however, one would expect this to underestimate the increased odds of survival in the rear middle seat. We also did not evaluate the number or type of injuries sustained by occupants involved in non-fatal crashes. 6. Conclusion The rear middle seat is the safest seating position for occupants when involved in a crash with at least one fatality. Proper restraint use coupled with this seating position provides the greatest protection for occupants of any age. References
4. Discussion This study shows that the safest seat in the vehicle is the rear middle seat. It was found that occupants of the rear seat are 29% safer than passengers in the front seat and occupants in the rear middle seat are 25% safer than other rear seat passengers. After controlling for factors such as seating position, restraint use, impact point, body type, age, and rollover, the rear middle seat is still statistically the safest seat in the vehicle (OR 1.133, 95% CI 1.02 - 1.26). It is logical that the rear middle seat is the safest seat as a result of the substantial distance between the passenger and point of impact in all crashes.
Braver, E. R., Whitfield, R., & Ferguson, S. A. (1998). Seating Position and Children's Risk of Dying in Motor Vehicle Crashes. Injury Prevention, 4, 181−187. Durbin, D. R., Chen, I., Smith, R., Elliott, M. R., & Winston, F. K. (2005). Effects of Seating Position and Appropriate Restraint Use on the Risk of Injury to Children in Motor Vehicle Crashes. Pediatrics, 115(3), e305−e309. Evans, L., & Frick, M. (1988). Seating Position in Cars and Fatality Risk. Am. J. Public Health, 78, 1456−1458. Johnson, D. L., & Falci, S. (1990). The Diagnosis and Treatment of Pediatric Lumbar Spine Injuries Caused by Rear Seat Lap Belts. Neurosurgery, 26, 434. LeGay, D. A., Petrie, D. P., & Alexander, D. I. (1990). Flexion-distraction Injuries of the Lumbar Spine and Associated Abdominal Trauma. Journal of Trauma, 30, 436.
436
J. Mayrose, A. Priya / Journal of Safety Research 39 (2008) 433–436
Mayrose, J., Jehle, V. K., Hayes, M., Tinnesz, D., Piazza, G., & Wilding, G. E. (2005). Influence of the Unbelted Rear-Seat Passenger on Driver Mortality: qThe Backseat Bullet. Academic Emergency Medicine, 12(2), 130−134. National Highway Traffic Safety Administration [NHTSA]. (2003). Fatality Analysis Reporting System (FARS). Traffic Safety Fact 2003 http://wwwfars.nhtsa.dot.gov/. Washington, DC: Author. National Highway Traffic Safety Administration [NHTSA]. (2005). Traffic Safety Notes. www.nhtsa.dot.gov Washington, DC: Author. Smith, K. M., & Cummings, P. (2004). Passenger Seating Position and the Risk of Passenger Death or Injury in Traffic Crashes. Accident Analysis & Prevention, 36(2), 257−260. Dr. Mayrose has been a member of the faculty in Mechanical Engineering Technology at Buffalo State College since 1999. He has been conducting research in the fields of Traumatic Injury and Biomechanics for the last 14 years. He has published over 40 abstracts and 25 articles in peer reviewed journals and has given 15 presentations at various national meetings. Dr. Mayrose has received over $5,000,000 in grant funding and was recently awarded “Inventor of the Year” by the Niagara Frontier Intellectual Property Law Association and Technical Societies Council for a US Patent he received.
Aruna Priya holds a masters degree in statistics. She is currently a doctoral student in the Department of Biostatistics at the University at Buffalo, NY. She have been providing statistical consultation/research assistance on various projects for physician and non-physician principal investigators, including at the emergency department, ECMC, Buffalo, NY.
www.nsc.org
The safest seat: Effect of seating position on occupant mortality James Mayrose ⁎, Aruna Priya Buffalo State College, Mechanical Engineering Technology, 1300 Elmwood Avenue, Buffalo, NY 14222 State University of New York at Buffalo, Department of Emergency Medicine, Buffalo, NY 14215 Available online 5 August 2008
Abstract Introduction: This study investigated the survival rates of occupants of passenger cars involved in a fatal crash between 2000 and 2003. Methods: The information from every fatal crash in the United States between 2000 and 2003 was analyzed. Variables such as seat position, point of impact, rollover, restraint use, vehicle type, vehicle weight, occupant age, and injury severity were extracted from the Fatality Analysis Reporting System (FARS). Univariate and a full logistic multivariate model analyses were performed. Results: The data show that the rear middle seat is safer than any other occupant position when involved in a fatal crash. Overall, the rear (2nd row) seating positions have a 29.1% (Univariate Analysis, p b .0001, OR 1.29, 95% CI 1.22 - 1.37) increased odds of survival over the first row seating positions and the rear middle seat has a 25% (Univariate Analysis, p b .0001, OR 1.25, 95% CI 1.17 - 1.34) increased odds of survival over the other rear seat positions. After correcting for potential confounders, occupants of the rear middle seat have a 13% (Logistic Regression, p b .001, 95% CI 1.02 - 1.26) increased chance of survival when involved in a crash with a fatality than occupants in other rear seats. Conclusion: This study has shown that the safest position for any occupant involved in a motor-vehicle crash is the rear middle seat. Impact on Industry: The results of this research may impact how automobile manufacturers look at future rear middle seat designs. If the rear seat was to be designed exactly like its outboard counterparts (headrest, armrests, lap and shoulder belt, etc.) people may choose to sit on it more often rather than waiting to use it out of necessity due to multiple rear seat occupants. © 2008 National Safety Council and Elsevier Ltd. All rights reserved. Keywords: Seating Position; Fatality; Crash; Safety
1. Introduction There were 42,643 traffic fatalities in the United States in 2003. Of those, 31,905 (75%) were occupants of passenger vehicles (cars, light trucks, vans, and SUV's). Of the 29,381 (92%) occupants for which restraint use was known, 16,593 (56%) were unrestrained at the time of the crash. Of these 29,381 occupants, 2,662 were rear seat occupants, 1,680 (68%) of which were unrestrained (National Highway Traffic Safety Administration [NHTSA], 2003). It is well known and widely accepted that the proper use of restraint systems saves lives and reduces the extent and number of injuries sustained by occupants involved in a motor-vehicle crash. There is also additional evidence in the literature documenting the reduced risk of injury and fatality to rear seat passengers as compared to front seat occupants. ⁎ Corresponding author. Tel.: +1 716 878 4802; fax: +1 716 878 3033. E-mail address: [email protected] (J. Mayrose).
A number of studies in the literature have also investigated the association of passenger seat position with the risk of death and serious injury when involved in a crash. One such study estimates that occupants in the rear seat of a passenger vehicle involved in a crash have a 39% reduced risk of death as compared to their front seat counterparts (Smith & Cummings, 2004). Another study documents an 18% decrease in fatalities for rear seat occupants wearing lap belts (Evans & Frick, 1988). Three point restraint systems and age appropriate safety systems have also been shown to provide even greater protection than lap belt only systems for rear seat occupants (Johnson & Falci, 1990; LeGay, Petrie, & Alexander, 1990). In regards to child safety, (Braver, Whitfield, & Ferguson, 1998) found that among children under 13 years of age, fatality risk was 38% lower for properly restrained rear seated children compared with those positioned in the front seat Braver et al. (1998). A more recent study by Winston et al. found children were 40% safer in the back seat than in the front when involved in a crash and that the risk of injury dropped to less than 2%
0022-4375/$ - see front matter © 2008 National Safety Council and Elsevier Ltd. All rights reserved. doi:10.1016/j.jsr.2008.06.003
434
J. Mayrose, A. Priya / Journal of Safety Research 39 (2008) 433–436
Table 1 Number of survivors by seat position and restraint use Seat Position No Restraint Used
Restraint Used
N
Front Seats
4,561
Rear Seats
7,512
Front Seats
8,332
Rear Seats
6,693
Table 2 Descriptive Data Occupant Position Subgroups
Survived (%)
Odds Ratio (95% CI)
p-value
2749 (60.3) 5306 (70.6) 7029 (84.4) 6087 (91.0)
1.585 (1.47 - 1.71)
P b.0001
1.862 (1.68 - 2.06)
p b .0001
when these rear seated children were harnessed in age appropriate restraint systems (Durbin, Chen, Smith, Elliott, & Winston, 2005). Although the literature suggests that the optimal seating location for passengers is the back seat of a vehicle and that children should use an age appropriate restraint system, it is unclear what the optimal location in the back seat is for properly restrained occupants of any age. In this study, we investigate the fatality rate of passengers seated in the rear middle seat versus those seated in other positions. 2. Methods A retrospective cohort study of fatal crash data concerning rear seat occupants involved in a fatal crash was obtained from the Fatality Analysis Reporting System (FARS), developed by the National Highway Traffic Safety Administration (NHTSA), for the years 2000 through 2003 (NHTSA, 2000-2003). Any vehicles with missing or unknown information regarding age, seat position, restraint use, injury severity, or vehicle type and weight were excluded from the study. A special class of crashes with a rear middle seat passenger was evaluated in order to compare the fatality rate of all rear seat occupants versus all front seat occupants. The numbers of fatalities in all of the front and rear seat occupant positions were compared. The information obtained from the FARS database with crashes involving rear seat occupants riding in a passenger vehicle was used to evaluate rear seat fatality risk. To assess whether the center rear seat is a safer seating position than either of the outboard rear seats, univariate analyses and multivariate logistic regression models were used. Chi-square analysis was used to test for statistical significance of the relationship between dichotomous variables. Odds ratios (OR) and confidence intervals were also calculated. Statistical significance was defined as p b 0.01. This study was approved by our Health Sciences Institutional Review Board.
Total Population N Occupant Age 0-4 5-8 9-16 N16 Restraint Use Yes No Injury Severity Lived Died
Outboard Seat
5707 (17.1%)
27611 (82.9%)
1631 (28.6%) 704 (12.3%) 1256 (22%) 2116 (37.1%)
4405 (16%) 2723 (9.9%) 6458 (23.4%) 14025 (50.7%)
2675 (46.9%) 3032 (53.1%)
15015 (54.4%) 12596 (45.6%)
4513 (79.1%) 1194 (20.9%)
20750 (75.2%) 6861 (24.8%)
passengers was 70.6% and 60.3% for unbelted front seat passengers. The survival rate was 91.0% for belted rear seat passengers and 84.4% for belted front seat passengers. Table 1 shows the lower fatality risk of the rear seating positions as well as the added protection seat belt use provides. The fatality rate for the rear middle seat position was then compared to both rear outboard seating positions. The FARS database included 34,470 rear seat occupants of passenger vehicles involved in fatal crashes that occurred over the 4 year study period. In this data set, we have complete records that met the study criteria on 33,318 (97%) occupants. The average age of the population was 20.09 years. Restraint use for the entire data set was 53.1% and the overall number of fatalities was 8,055 (24.2%). Rear seat passengers were placed in one of two groups based on their seating position at the time of the crash. The middle seat group contained 5,707 (17.1%) occupants, while the outboard seat group contained 27,611 (82.9%) occupants. The average age of the middle seat occupants was 15.45 years versus 21.05 for the outboard occupants. Table 2 shows the descriptive statistics for each of the two groups of occupants. Chi Square analysis comparing the two groups by injury severity (Lived or Died) and any restraint use (Yes or No) was performed. A statistically significant difference was found (p b .001) where middle seat occupants, whether restrained or unrestrained, had a higher rate of survival than outboard occupants (Table 3). The primary statistical tool used in the second step of the analysis was logistic regression where the outcome of the analysis was survival of the rear seat occupant involved in the crash. The primary variables of interest were seating position, principal impact point, rollover, restraint use, age, and body type. The results of this analysis show that occupants of the rear Table 3 Survival of belted versus unbelted occupants by seating position
3. Results There were 27,098 occupants of motor vehicles involved in a fatal crash between 2000 and 2003 where a rear middle seat passenger was present. The survival rate for unbelted rear seat
Middle Seat
Middle Seat
Restrained Unrestrained
Outboard Seat
Lived
Died
Lived
Died
2386 (89.2%) 2127 (70.2%)
289 (10.8%) 905 (29.8%)
12663 (84.3%) 8087 (64.2%)
2352 (15.7%) 4509 (35.8%)
J. Mayrose, A. Priya / Journal of Safety Research 39 (2008) 433–436 Table 4 Logistic Regression Model for Significant Variables (Survival) Odds Ratio Estimates for Rear Seat Occupants (Survival) Effect Middle Seat Rollover Restraint Use Impact Point Impact Point Body Type Body Type Age Group Age Group
Point 95% Wald Estimate Confidence Limits Middle seat vs. Any side seat No Rollover vs. Rollover Restraint Used vs. Not Used Front vs. Side Front vs. Rear Van/SUV vs. Cars Van/SUV vs. Pickup 0-4 years vs. above 16 years 5-15 years vs. above 16 years
1.133 1.491 2.801 2.205 2.274 1.817 1.175 1.276 1.558
1.015 1.318 2.637 2.045 2.065 1.551 1.036 1.171 1.458
1.264 1.687 2.976 2.376 2.504 2.129 1.331 1.391 1.664
middle seat are safer than those seated in either of the rear outboard positions. The estimated odds of survival for a rear middle seat occupant is 1.25 (Univariate Analysis, p b .0001, 95% CI 1.17-1.34,) times that for a rear seat outboard occupant. In addition, the estimated odds of survival for restrained rear seat occupants are 3.16 (95% CI 2.99-3.33, p b .0001) times that for unrestrained rear seat occupants. The data also show that rear seat occupants involved in a head-on crash have a higher probability of survival as opposed to any other point of impact (OR N 2, p b .0001). Age and vehicle type were also significant factors for estimating the survival of rear seat occupants. Children age 15 and younger are two times more likely to survive a crash than older rear seat occupants. Rear seat occupants of SUV's are 1.71 and 1.21 times more likely to survive a crash than rear seat occupants of passenger cars and pickup trucks, respectively. After testing the univariate models for all variables of interest, variables found to be significant along with their interaction variables were fit into a full logistic model that included all logical interaction terms. As is shown in Table 4, the odds of survival for occupants of the rear middle seat are 1.133 (95% CI 1.015 - 1.264) times higher than other rear seated occupants. Restrained rear seat occupants are also 2.801 (95% CI 2.637 - 2.976) times more likely to survive the crash than unrestrained rear seat passengers. The results of the odds estimates of survival coincide with the results obtained in the univariate analysis. All the variables of interest show a statistically significant effect on survival based on occupant position.
435
Although front seat belt use rates continue to climb year after year and have reached an all time high of 80% nationwide in 2004, rear seat occupants still have a very low restraint use rate as is seen from this data (NHTSA, 2005). In addition, belt use rates in crashes with a fatality tend to be lower than observed belt use rates in the total population (Mayrose et al., 2005). In this current study, nearly half (46.9%) of the 33,318 occupants riding in the rear seat were unrestrained. Of these unrestrained occupants, 34.6% were fatally injured in the crash while only 14.9% of restrained occupants were killed. The multivariate analysis for restraint use showed an odds estimate of 2.801 (p b .0001, 95% CI 2.637 - 2.976), which represents the likelihood a restrained rear seat passenger has of surviving a crash versus that of an unrestrained rear seat passenger. The analysis also revealed a number of other variables that have a significant effect on rear seat occupant survival when involved in a fatal crash. Body type, Impact Point, Rollover, age, restraint use, and seating position were all found to have a significant effect on survival. The data in this study shows a strong association between occupant seat position and survivability of a crash. Other studies have investigated the lower fatality risk of riding in the rear seat but only for selected samples of children without controlling for potential confounders (Evans & Frick, 1988; Braver, Whitfield, & Ferguson, 1998). 5. Limitations It has been shown in the literature that occupants of a crash restrained by only a lap belt suffer more extensive injuries compared with those occupants restrained with a lap/shoulder safety belt system. The extent of injuries to rear middle seat occupants due to the use of only a lap belt were not investigated in this study, however, one would expect this to underestimate the increased odds of survival in the rear middle seat. We also did not evaluate the number or type of injuries sustained by occupants involved in non-fatal crashes. 6. Conclusion The rear middle seat is the safest seating position for occupants when involved in a crash with at least one fatality. Proper restraint use coupled with this seating position provides the greatest protection for occupants of any age. References
4. Discussion This study shows that the safest seat in the vehicle is the rear middle seat. It was found that occupants of the rear seat are 29% safer than passengers in the front seat and occupants in the rear middle seat are 25% safer than other rear seat passengers. After controlling for factors such as seating position, restraint use, impact point, body type, age, and rollover, the rear middle seat is still statistically the safest seat in the vehicle (OR 1.133, 95% CI 1.02 - 1.26). It is logical that the rear middle seat is the safest seat as a result of the substantial distance between the passenger and point of impact in all crashes.
Braver, E. R., Whitfield, R., & Ferguson, S. A. (1998). Seating Position and Children's Risk of Dying in Motor Vehicle Crashes. Injury Prevention, 4, 181−187. Durbin, D. R., Chen, I., Smith, R., Elliott, M. R., & Winston, F. K. (2005). Effects of Seating Position and Appropriate Restraint Use on the Risk of Injury to Children in Motor Vehicle Crashes. Pediatrics, 115(3), e305−e309. Evans, L., & Frick, M. (1988). Seating Position in Cars and Fatality Risk. Am. J. Public Health, 78, 1456−1458. Johnson, D. L., & Falci, S. (1990). The Diagnosis and Treatment of Pediatric Lumbar Spine Injuries Caused by Rear Seat Lap Belts. Neurosurgery, 26, 434. LeGay, D. A., Petrie, D. P., & Alexander, D. I. (1990). Flexion-distraction Injuries of the Lumbar Spine and Associated Abdominal Trauma. Journal of Trauma, 30, 436.
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J. Mayrose, A. Priya / Journal of Safety Research 39 (2008) 433–436
Mayrose, J., Jehle, V. K., Hayes, M., Tinnesz, D., Piazza, G., & Wilding, G. E. (2005). Influence of the Unbelted Rear-Seat Passenger on Driver Mortality: qThe Backseat Bullet. Academic Emergency Medicine, 12(2), 130−134. National Highway Traffic Safety Administration [NHTSA]. (2003). Fatality Analysis Reporting System (FARS). Traffic Safety Fact 2003 http://wwwfars.nhtsa.dot.gov/. Washington, DC: Author. National Highway Traffic Safety Administration [NHTSA]. (2005). Traffic Safety Notes. www.nhtsa.dot.gov Washington, DC: Author. Smith, K. M., & Cummings, P. (2004). Passenger Seating Position and the Risk of Passenger Death or Injury in Traffic Crashes. Accident Analysis & Prevention, 36(2), 257−260. Dr. Mayrose has been a member of the faculty in Mechanical Engineering Technology at Buffalo State College since 1999. He has been conducting research in the fields of Traumatic Injury and Biomechanics for the last 14 years. He has published over 40 abstracts and 25 articles in peer reviewed journals and has given 15 presentations at various national meetings. Dr. Mayrose has received over $5,000,000 in grant funding and was recently awarded “Inventor of the Year” by the Niagara Frontier Intellectual Property Law Association and Technical Societies Council for a US Patent he received.
Aruna Priya holds a masters degree in statistics. She is currently a doctoral student in the Department of Biostatistics at the University at Buffalo, NY. She have been providing statistical consultation/research assistance on various projects for physician and non-physician principal investigators, including at the emergency department, ECMC, Buffalo, NY.