March 2005 DOT HS 809 778

Lives Saved Calculations for Infants and Toddlers

Marc Starnes*

Traffic Safety Facts

Research Note

NHTSA’s National Center for Statistics and Analysis 400 Seventh St., S.W., Washington, D.C. 20590

*Marc Starnes is a Mathematical Statistician in the Mathematical Analysis Division, National Center for Statistics and Analysis, NHTSA.

Summary

The effectiveness of a vehicle restraint system (e.g., child 

safety seat, lap and/or shoulder belts) measures the protection 

provided by that restraint use in preventing a traffic fatality. 

The National Highway Traffic Safety Administration (NHTSA) 

has calculated estimates for the effectiveness of various 

restraint systems through analyses of data from the Fatality 

Analysis Reporting System (FARS). These effectiveness 

estimates are used in this report to calculate the number of 

infant and toddler lives saved in 2003 through the use of child 

safety seats and lap and/or shoulder belts.

Table 1 contains child safety seat effectiveness estimates. 

The rate of effectiveness for infants in child safety seats in 

passenger cars means that 71 percent of infants in passenger 

cars who would die without a child safety seat would survive 

the crash if they were restrained in a child safety seat. Table 2 

contains lap and/or shoulder belt effectiveness estimates. 

A summary of estimates for the effectiveness of child restraints 

was published in the research note Revised Estimates of 

Child Restraint Effectiveness (Hertz, 1996). The estimates 

are stratified by vehicle type (passenger cars, or light trucks 

and vans) and the age of the child (infant: less than one year 

old; toddler: 1–4 years old). 

Beginning with FARS 2003 data, an effectiveness of zero 

percent has been applied to infants in lap and/or shoulder 

belts. This zero percent effectiveness means that an infant 

placed in a lap and/or shoulder belt is no more or less likely to 

survive a crash than an infant who is unrestrained.

Table 1

Estimated Fatality Reducing Effectiveness 

Of Child Safety Seats

Vehicle Type

Age Group

Infants

(up to Age 1)

Toddlers

(1-4 years)

Passenger Cars 71% 54%

Light Trucks and Vans 58% 59%

Source: NCSA, NHTSA

Vehicle Type

Age Group

Infants 

(up to Age 1)

Toddlers 

(1-4 years)

Passenger Cars 0% 47%

Light Trucks and Vans 0% 48%

Source: NCSA, NHTSA

Methodology

In order to calculate the number of lives saved by child safety 

seats and lap and/or shoulder belts, the following variable 

definitions and formulas will be used.

F = number of fatalities, by restraint type, age category, and 

vehicle type

E = estimated effectiveness, by restraint type, age category, 

and vehicle type

Stratified by restraint use, age category, and vehicle type, the 

number of potential fatalities is estimated to be

Potential fatalities = F

1 — E

and the number of lives that were saved is estimated to be

Lives saved = E* F

1 — E

The number of potential lives saved is based on the 

assumption that child safety seats are the most effective child 

restraint for infants and toddlers. For infants and toddlers in 

child safety seats, the number of lives saved is equal to the 

number of potential lives saved, given that child safety seats 

are the most effective restraint type for infants and toddlers.

Children under 5 years old whose restraint use was coded as 

“Child Safety Seat” or “Child Safety Seat Used Improperly” 

were considered restrained in a child safety seat. Children 

whose restraint use was “Shoulder Belt,” “Lap Belt,” “Lap 

and Shoulder Belt,” or “Safety Belt Used Improperly” were 

Table 2

Estimated Fatality Reducing Effectiveness 

Of Lap and/or Shoulder Belts
NHTSA’s National Center for Statistics and Analysis 2 400 Seventh St., S.W., Washington, D.C. 20590

grouped into the “Lap and/or Shoulder Belt” restraint 

use category. Those children with a restraint use variable 

coded as “None Used/Not Applicable” were considered 

unrestrained. Children whose restraint use was coded 

as “Unknown” were prorated between the restrained and 

unrestrained categories. 

Children whose restraint use was coded as “Restraint Used, 

Type Unknown” were pro-rated between the two restraint 

categories, child safety seat and lap and/or shoulder belt. 

The prorated fatality counts in the table below have been 

rounded off to the nearest integer.

In addition to restraint use, age category, and vehicle 

type, other variables were examined yet were not included 

inthe effectiveness estimates listed below due to a lack of 

heterogeneity among their differing categories. 

Changes

The increasing popularity of light trucks and vans (LTV) led 

Hertz (1996) to calculate separate child safety seat and lap 

and/or shoulder belt effectiveness numbers for passenger 

cars and LTVs. Hertz’s effectiveness numbers were first 

implemented with 2002 FARS data to calculate the number 

of lives saved among infants and toddlers. These updated 

effectiveness numbers were calculated using the same paired 

comparison methodology reported in Lives Saved by Child 

Restraints from 1982 through 1987 (Partyka, 1988). 

Partyka, using FARS data from 1982 through 1987, estimated 

child safety seats to be 69 percent effective against fatalities for infants and 47 percent effective for toddlers; adult seat 

belts were estimated to be 36 percent effective for children up 

through 4 years old. Given the 1980s’ proliferation of passengers cars, Partyka’s estimates were created to apply only to 

passenger cars and did not include light trucks and vans.

In addition to incorporating Hertz’s updated effectiveness 

estimates, the infant and toddler lives saved calculations 

made with 2002 and/or 2003 FARS data include a change 

in the definition of child safety seats. The restraint use 

categories “Child Safety Seat” and “Child Safety Seat Used 

Improperly” are combined, to reflect the methodology that 

Hertz used to calculate the effectiveness estimates. Before 

this change, a child whose restraint use was “Child Safety 

Seat Used Improperly” was considered unrestrained.

In 2002, the National Occupant Protection Use Survey 

(NOPUS) estimated that 98 percent of infants traveled in child 

safety seats. In 2003, FARS data showed that zero infants 

were fatally injured in lap and/or shoulder belts. Given the 

limited use of lap and/or shoulder belts by infants, NHTSA 

has determined there to be insufficient data to estimate an 

effectiveness for lap and/or shoulder belts for children under 

one year old. Therefore, the effectiveness for lap and/or 

shoulder belts was updated in 2003 to be 0 percent for 

infants. This effectiveness figure states that infants are neither 

more safe nor less safe travelling in lap and/or shoulder belts, 

compared to travelling unrestrained.

Results

Lives saved estimates using the new methodology are 

illustrated in Table 3 using 2003 FARS fatality counts. Table 

4, also using 2003 FARS fatality counts, is an example of the 

lives saved methodology which was used prior to the changes 

implemented in 2002 and 2003. 

Separate lives saved calculations are shown for each combination of vehicle type, child’s age, and restraint use type. 

Table 3 shows that infants and toddlers in child safety seats in 

passenger cars accounted for an estimated 309 lives saved 

in 2003. In light trucks and vans, an estimated 89 infants and 

toddlers had their lives saved due to being restrained in child 

safety seats. In 2003, lap and/or shoulder belts saved an 

estimated 45 lives among toddlers in passenger cars or light 

trucks and vans. Overall, an estimated 443 infant and toddler 

lives were saved in 2003, an increase of 67 over the 376 lives 

saved during the year of 2002.

 The change in lives saved methodology for infants and toddlers 

is displayed by comparing Table 3 (New Methodology) and 

Table 4 (Previous Methodology). Table 3 is produced using 

the current effectiveness numbers, while Table 4 is produced 

with the effectiveness numbers that were used prior to 2002. 

These two tables both provide estimates of lives saved in 

2003.

For all four combinations of vehicle type and age group, the 

new fatality counts for children in child safety seats climbed 

an amount equal to the corresponding decline in fatalities 

among unrestrained children. This transfer of fatalities from 

one restraint use category to another was due to the shift 

of the “child safety seat used improperly” restraint category 

from “unrestrained” to “child safety seat.” 

This shift, when combined with the new effectiveness 

estimates, led to a large increase in the lives saved estimates 

involving the use of child safety seats. For example, among 

toddlers in passenger cars, the number of child safety 

seat fatalities in 2003 would have been 105 using the old 

methodology, yet rose to 126 with the new methodology. The 

corresponding lives saved estimation for this category would 

have been 94 with the old methodology, and was 147 with the 

new methodology. 

Lap/shoulder belt effectiveness estimates among toddlers 

rose 11 percentage points for passenger cars (from 36 

percent to 47 percent) and 12 percentage points for LTVs 

(from 36 percent to 48 percent). This rise in effectiveness 

caused the estimated number of toddler lives saved by a 

lap and/or shoulder belt to increase from 20 to 31 among 

passenger cars, and from 9 to 14 among LTVs. For infants, 

lap and/or shoulder belt effectiveness dropped from 36 

percent to zero percent. This drop in effectiveness did not 

change the number of lives saved for 2003, as no infants in 

lap and/or shoulder belts were fatally injured in 2003.
NHTSA’s National Center for Statistics and Analysis 3 400 Seventh St., S.W., Washington, D.C. 20590

The increase in lives saved by child safety seats and lap and/

or shoulder belts caused the overall number of estimated 

lives saved for infants and toddlers in 2003 to increase 

substantially to 443 lives saved. Using the old methodology 

(Table 4), the number of estimated lives saved in 2003 would 

have been limited to 289.

For both the old methodology and the new methodology, 

the estimated lives saved counts for unrestrained children 

remained at zero for each combination of vehicle type and 

age group. 

Table 3

New Methodology: Estimated Lives Saved Among Infants and Toddlers Through Child Safety Seat (CSS) or Lap and/or 

Shoulder Belt (L/S) Usage, FARS 2003

Vehicle Type Child’s Age Restraint Type Effectiveness Fatalities Potential 

Fatalities

Lives 

Saved

Potential 

Lives Saved

Passenger Cars Infant CSS 71 % 66 228 162 162

Passenger Cars Infant L/S 0 % 0 0 0 0

Passenger Cars Infant None 0 % 19 19 0 13

Passenger Cars Toddler CSS 54 % 126 273 147 147

Passenger Cars Toddler L/S 47 % 35 65 31 35

Passenger Cars Toddler None 0 % 73 73 0 39

Light Trucks and Vans Infant CSS 58 % 21 49 28 28

Light Trucks and Vans Infant L/S 0 % 0 0 0 0

Light Trucks and Vans Infant None 0 % 12 12 0 7

Light Trucks and Vans Toddler CSS 59 % 42 103 61 61

Light Trucks and Vans Toddler L/S 48 % 15 29 14 17

Light Trucks and Vans Toddler None 0 % 63 63 0 37

Note: Potential Fatalities may not equal sum of Fatalities and Lives Saved due to independent rounding. Fatalities where restraint use 

was unknown have been prorated between the restraint use categories and included in this table.

Vehicle Type Child’s Age Restraint Type Effectiveness Fatalities Potential 

Fatalities Lives Saved Potential Lives Saved

Passenger Cars Infant CSS 69 % 51 166 114 114

Passenger Cars Infant L/S 36 % 0 0 0 0

Passenger Cars Infant None 0 % 34 34 0 23

Passenger Cars Toddler CSS 47 % 105 199 94 94

Passenger Cars Toddler L/S 36 % 35 54 20 26

Passenger Cars Toddler None 0 % 93 93 0 44

Light Trucks and Vans Infant CSS 69 % 11 37 25 25

Light Trucks and Vans Infant L/S 36 % 0 0 0 0

Light Trucks and Vans Infant None 0 % 22 22 0 15

Light Trucks and Vans Toddler CSS 47 % 32 59 28 28

Light Trucks and Vans Toddler L/S 36 % 15 24 9 11

Light Trucks and Vans Toddler None 0 % 73 73 0 34

Note: Potential Fatalities may not equal sum of Fatalities and Lives Saved due to independent rounding. Fatalities where restraint use 

was unknown have been prorated between the restraint use categories and included in this table.

Table 4

Previous Methodology: Estimated Lives Saved Among Infants and Toddlers Through Child Safety Seat (CSS) or Lap and/or 

Shoulder Belt (L/S) Usage, FARS 2003
NHTSA’s National Center for Statistics and Analysis 4 400 Seventh St., S.W., Washington, D.C. 20590

References

Hertz, Ellen. Revised Estimates of Child Restraint 

Effectiveness, NHTSA Research Note, December 1996.

Partyka, Susan. Lives Saved by Child Restraints from 

1982 through 1987, DOT HS 807 371, December 1988. 

For additional copies of this research note, please call 

800-934-8517 or fax your request to 202-366-3189. For 

questions regarding the data reported in this research, 

contact Marc Starnes [202-366-0183]. This research note 

and other general information on highway traffic safety may 

be accessed by Internet users at: www-nrd.nhtsa.dot.gov/

departments/nrd-30/ncsa/AvailInf.html