CHAPTER V. POTENTIAL BENEFITS
This chapter estimates the potential benefits of using Hybrid III dummies and incorporating FMVSS 208 head, neck, and chest injury criteria and the corresponding ICPLs. The calculation is based on limited FMVSS 213 sled pulse tests. The agency believes that the proposed seat assembly and crash pulse has a same overall performance as does the current standard. Thus, these changes would not alter the stringency of the compliance test and would likely no benefit impacts.
The chapter is organized into four sections. The first section describes the benefit estimation methodology. The second section estimates the target population represented by each dummy size. The third section presents the fatality and MAIS 25 nonfatal injury reduction rates. Finally, the fourth section estimates the potential benefits.
A. Overview of Methodology
The benefit estimation process consists of six steps: (1) identify the target population; (2) estimate the fatality/injury probabilities; (3) calculate the fatality/injury reduction rates; (4) calculate the total weighted fatality/injury reduction rates; (5) calculate the combined head, neck, chest fatality/injury reduction rate; and (6) derive benefits. The following is a detailed description of each step.
Step 1: Identify target population. The FMVSS 213 test is designed to assess child restraint safety in frontal impacts. Therefore, the target population would be all the child passenger vehicle occupant fatalities and injuries in a CRS in frontal crashes. However, the agency believes that the proposed new requirements would have a minimal impact on nonfatal MAIS 1 injuries because the majority of these were skin bruise injuries. Thus, the target population for nonfatal injuries was limited to MAIS 25 injuries. In addition, the agency assumes that the new proposal would impact children in a properly used CRS with a MAIS head, neck, or chest injury. As a result, the target population used for the benefit calculation includes the child occupants in a properly used CRS who had a fatal or a MAIS 25 head, neck or chest injury. Based on NHTSA's data systems, child restraints were properly used in 82 of 100 fatalities and 1,800 of 1,818 nonfatal MASI 25 injuries.
The target population represented by the 12monthold CRABI is children 1 year old and younger; represented by the 3yearold dummy is children aged 2 to 3 years old; represented by the 6yearold dummy is children aged 4 to 6 years old, and represented by the weighted 6yearold dummy were children aged 7 to 10 years old who weigh less than 66 pounds. The target population is summarized in Table V1.
Step 2: Estimate the fatality/injury probabilities. For each injury criterion, the corresponding injury probability curves were used to estimate the injury probabilities for each test failing the proposed ICPL. For example, if a dummy measurement was an Nij of 1.5, the child, regardless of child size, would have an 11.7 percent chance of dying from the neck injury and a 31.9 percent chance of receiving a MAIS 25 neck injury. The baseline fatal probability for Nij at the proposed level of the standard (i.e., Nij=1), is 6.8 percent and baseline MAIS 25 injury probability is 23.0 percent.
Step 3: Calculate the fatality/injury reduction rates. After estimating the injury probability, the reduction rate (r) was calculated for each test failing the ICPL by injury criteria. The reduction has the form: ,
Where p_{t} = fatality/injury probability at the crash test level,
p_{ICPL} = fatality/injury probability at the proposed ICPL level.
For example, a CRS test failed at Nij=1.5. The fatality and MAIS 25 injury reduction rates for this CRS would be 41.9 [=(11.76.8)/11.7] and 27.8 [=(31.923.0)/31.9] percent, respectively, after implementing the proposal.
Step 4: Calculate the total weighted reduction rates. For each dummy size, the total weighted fatality and MAIS 25 injury reduction rates were calculated separately for each injury criterion, i.e., HIC, neck, chest g, and chest deflection. The total reduction rate was derived using the formula:
r = w_{ i} * r_{ i , } i {1,2,3,...k}
Where
r = the total fatality/injury reduction rate
w_{ i} = the proportion of the specific CRS market share
r_{ i }= the fatality/injury reduction rate from Step 3
k = the number of CRSs failing to meet the specific injury ICPL
The analysis, however, is unable to obtain the market share of each CRS on the market today. The Juvenile Products Manufacturers Association (JPMA) has not been willing to share the information with the agency during the report publication time. The agency believes that the CRSs tested represent those more popular brands on the market, thus, the analysis gives each CRS tested an equal weight, i.e., w_{ i}= 1/n for every i. The number n is the total number of CRS tested within the same dummy group.
Step 5: Calculate the combined head, neck, and chest fatality/injury reduction rate. The combined head, neck, and chest reduction is:
C = w_{HIC} * r_{HIC} + w_{Nij} * r_{Nij} + w_{chest} * r_{chest }  w_{HIC} * r_{HIC} * w_{Nij} * r_{Nij}  w_{HIC} * r_{HIC} * S
Where, w_{i} is the weight, and
The weight is the normalized proportion of the injured body region. These weights were derived from the percentage distribution shown in Table II6. The weights for HIC, Nij, and chest fatalities are 90 percent [=0.71/(0.71+0.01+0.07)] for HIC, 1% for Nij, and 9 percent for chest fatal injury. The corresponding weights for MAIS 25 HIC, neck, and chest injuries are: 88 percent [=0.43/(0.43+0.0012+0.06)], 0.2 percent, and 12 percent, respectively. Note that both chest g's and chest deflection predict chest injuries, thus only the maximum of these two reduction rates was used in the combined reduction rate calculation, i.e., r_{chest } = maximum of (r_{chest g}, r_{chest deflection})
Step 6: Estimate Benefits. The last step is to apply the combined reduction rate derived from Step 5 to the corresponding population to estimate benefits:
B = TP * C
Where, B = benefits (lives that would be saved or MAIS 25 injuries that would be reduced
B. Target Population
The target population as defined in the methodology section is all the child occupant fatalities and MAIS 25 injuries seated in a properly used CRS when a frontal impact occurred. These occupants had a MAIS 2+ head, or neck, or chest injury. Table V1 (adapted from Table II7) shows the target child population that would be impacted by the proposed new dummy and injury criteria by age and orientation of CRS. Because the target population is small, the analysis does not segregate the target population further by injured body region.
Annually, there are about 65 fatalities and 891 MAIS 25 nonfatal injuries as shown in Table V1 that could be impacted by the new proposal. The target population represented by the 12monthold CRABI was children 1 year old and younger. These included 37 infant fatalities and 445 MAIS 25 injuries. Represented by the 3yearold dummy were children aged 2 to 3 including 22 fatalities and 406 MAIS 25 injuries. Represented by the 6yearold dummy were children aged 4 to 6 years old including 5 fatalities and 40 MAIS injuries. Represented by the weighted 6yearold dummy were children aged 7 to 10 years old with weight less than 66 pounds. This group included only 1 fatality.
Table V1
Children in Properly Used Child Restraint System (CRS)
With a MAIS 2+ Head, Neck, or Chest Injury
Age  Forward Facing CRS  Rear Facing CRS  Total 

Fatalities  
01 Years Old  21  16  37 
23 Years Old  22  0  22 
46 Years Old  5  0  5 
710 Years Old  1  0  1 
Total  49  16  65 
MAIS 25 Injuries  
01 Years Old  259  186  445 
23 Years Old  406  0  406 
46 Years Old  40  0  40 
710 Years Old  0  0  0 
Total  705  186  891 
The target population is derived based on the NHTSA collected realworld crash data: the 1999 FARS, 19932000 CDS, and 1999 GES. The child fatalities and MAIS 25 nonfatal injuries were derived from 19932000 CDS and adjusted to 1999 FARS level and 1999 GES CDSequivalent level, respectively. The 1999 FARS and GES are the most currently available fatality and injury data.
C. Fatality and Injury Reduction Rates
Table V2 represents the total fatality and MAIS 25 nonfatal injury reduction rates by dummy size and injury criteria. The FMVSS 213 pulse sled test data were used to derive these reduction rates. Both chest g's and chest deflection predict the chest injury, thus, only the maximum of these two reduction rates was used to calculate the HIC_{15}/Nij/Chest combined reduction rate. These weights are the normalized proportion of the injury body region as described in the methodology section. For fatalities, the weights are 90 percent [=0.71/(0.71+0.01+0.07)], for HIC_{15}, 1 percent for Nij and 9 percent for chest. For MAIS 25 injuries, the corresponding weights are 88 percent [=0.43/(0.43+0.0012+0.06)], 0.2 percent, and 12 percent (the bigger of the chest g's and chest deflection), respectively.
As shown in Table V2, the highest reduction rates were from reducing neck injury values. However, neck injury carries the least weight in the calculation because of the small target population. The combined head, neck, and chest fatality reduction rates are shown in Table V2.
Table V2
Fatality and MAIS Injury Reduction Rates
by Dummy Size and Injury Criteria
Dummy Size  HIC_{15} Prasad/Mertz (Lognormal) 
Nij  Chest g's 
Chest Deflection 
Combined HIC_{15}+Nij+Chest 

Fatality Reduction Rate  
CRABI  

0.0% (0.0%) 
19.9%  6.5%  na  0.83% (0.83%) 

23.9% (16.7%) 
20.3%  14.3%  na  22.99% (16.49%) 

0.0% (0.0%) 
5.0%  0.0%  0.0%  0.06% (0.06%) 

15.5% (9.9%) 
16.1%  0.0%  0.0%  14.16% (9.12%) 

0.0% (0.0%) 
2.8%  0.0%  0.0%  0.04% (0.04%) 
MAIS 25 Injury Reduction Rate  
CRABI  

0.0% (0.0%) 
13.3%  0.5%  Na  0.09% (0.09%) 

2.1% (1.9%) 
13.6%  1.1%  Na  2.02% (1.82%) 

0.0% (0.0%) 
3.4%  0.0%  0.0%  0.01% (0.01%) 

1.4% (1.6%) 
10.9%  0.0%  0.0%  1.29% (1.41%) 

0.0% (0.0%) 
1.9%  0.0%  0.0%  0.01% (0.01%) 
D. Benefits
The potential benefits are estimated by applying the HIC/Nij/chest combined reduction percentages shown in Table V2 to the corresponding target population in Table V1. As shown in Table V3, the estimated benefits for adapting the FMVSS 208 scaled child injury criteria and corresponding ICPLs would save 35 children age 01 year old and mitigate 5 MAIS 25 injuries in a forwardfacing CRS. The proposed amendment also would save 1 child age 46 years old and mitigate 1 MAIS 25 injuries of the same age group in a booster seat. The estimated benefits reflect the 14 percent of CRS use in fatal frontal crashes and 20 percent in MAIS 25 frontal injuries. If more children, especially older children, were restrained in a CRS, the benefits would be higher.
Table V3
Estimated Fatality and MAIS 25 Injury Benefits
Child's Age  Estimated Benefits 

Fatality  
0  1 Year Old  
RearFacing  0 
ForwardFacing  35* 
2  3 Years Old  0 
4  6 Years Old  1 
7  10 Years Old (< 66 pounds)  0 
MAIS 25 Injuries  
0  1 Year Old  
RearFacing  0 
ForwardFacing  5 
2  3 Years Old  0 
4  6 Years Old  1 
7  10 Years Old (< 66 pounds)  0 