NHTSA’s National Center for Statistics and Analysis 400 Seventh St, SW, Washington DC 20590

August 2005 DOT HS 809 861

Calculating Lives Saved by Motorcycle Helmets 

William V. Deutermann*

Based on a comparison of fatal crashes involving 

motorcycles with two riders, at least one of whom was 

killed, the National Center for Statistics and Analysis 

(NCSA) of the National Highway Traffic Safety 

Administration (NHTSA) has estimated helmets to be 

about 37 percent effective in preventing fatalities.1

 In 

2003, there were 3,661 rider deaths in fatal motorcycle 

crashes. An effectiveness of 37 percent for motorcycle 

helmets suggests that an estimated 1,158 additional 

motorcyclists would have died were it not for the fact that 

they were wearing helmets. Had all motorcyclists 

consistently worn proper helmets, an additional 640 

motorcyclists could have survived otherwise fatal crashes 

in 2003. Unfortunately, the potential lifesaving benefits of 

helmets are not being realized, as fatalities continue to 

rise in response to declining helmet usage rates. 

According to the 2002 National Occupant Protection Use 

Survey, only 58 percent of motorcyclists nationally were 

observed to be wearing helmets2

. This represents a 

dramatic decline since 2000, when the usage rate was 71 

percent. 

Despite the fact that less than 3 percent of registered 

passenger vehicles are motorcycles, motorcyclist fatalities 

represent about 9 percent of all passenger vehicle rider 

fatalities. Considering that passenger car rider fatalities are 

trending downward, policies that result in raising public 

acceptance of the protective value of helmets can have a 

significant impact on reducing the total number of lives 

lost annually on America’s highways. 

Periodically, NCSA publishes an estimate of lives saved 

by various policies and strategies. This note describes the 

methodology used to calculate the contribution of 

motorcycle helmets to the total number of lives saved. 

Calculation of Lives Saved

The starting point for estimating lives saved by helmets 

is to establish the effectiveness of helmets. In past years, 

NCSA has used a figure of .29 for effectiveness. This 

figure was based on cumulative fatal crash mortality data 

in the Fatality Analysis Reporting System (FARS) files 

from 1982 through 1987. In 2004, NCSA produced a 

revised estimate of .37 effectiveness based on more 

recent data to reflect changes that may have occurred in 

helmet materials and design since 1987.3

 The estimate of 

effectiveness is a composite of the separate effectiveness 

of helmets in protecting the lives of motorcycle 

operators and passengers. 

If the total number of motorcyclists who died despite the 

protection of their helmets is known, then there must be 

a potential number of fatally injured helmeted 

motorcyclists that includes the number whose lives were 

spared due to their helmets. The number of Lives Saved 

(LS), therefore, must be equal to Fatalities Potential, the 

potential fatalities, multiplied by the effectiveness: 

LS= Fatalities Potential * .37 

The number of potential fatalities is unknown, but we do 

know that the number of helmeted fatalities is equal to 

the number of potential fatalities reduced by the 

complement of the effectiveness, or 

Fatalities Helmeted= Fatalities Potential * (1-.37) 

And Potential fatalities are: 

Fatalities Potential = Fatalities Helmeted / (1-.37) 

Returning to Lives Saved, we now have: 

LS = Fatalities Potential * .37 

Or 

LS = Fatalities Helmeted *.37/ (1-.37) 

*William V. Deutermann is a mathematical statistician with the Mathematical Analysis Division of the National Center for Statistics and Analysis, NHTSA. 
NHTSA’s National Center for Statistics and Analysis 2 400 Seventh St, SW, Washington DC 20590

Now let us assume that we are living in an ideal society 

in which all motorcyclists take it upon themselves to 

wear proper helmets at all times while riding. How many 

lives would be saved with 100 percent compliance? 

The number of Potential Lives Saved (PLS) would equal 

the sum of the estimated Lives Saved and the total 

number of fatalities, both helmeted and unhelmeted, 

multiplied by the effectiveness of helmets: 

PLS = (Fatalities Total + LS) * .37 

Sample Calculations 

The calculations are carried out using the effectiveness 

rates separately for operators and passengers, and then 

summing the results to obtain an estimate of Lives Saved 

that reflects a weighted average of the two effectiveness 

rates. The effectiveness for operators is estimated as .37, 

while the estimate for passengers is higher at .41. An 

example of the calculation using the 2003 FARS 

motorcyclist fatality data follows: 

LS Operators = 1,805 (.37/(1-.37)) 

 = 1,060 

LS Passengers = 141 (.41/(1-.41)) 

 = 98 

And Total LS = 1,158 

For Potential Lives Saved in 2003: 

PLS Operators = (Fatalities + LS ) Operators * .37 

= (3,382 + 1,060) * .37 

= 1,644 

PLS Passenger = (Fatalities + LS ) Passengers * .41 

= (279 + 98) * .41 

=154 

And Total Potential Lives Saved = 1,798 

The data used in the calculation are shown in table 1. 

 

Impact on Estimates of Lives Saved 

Although the method of estimating lives saved by 

helmets has not changed, adoption of the new 

effectiveness rate will tend to increase the estimates. 

Because it is calculated from cumulative data over a tenyear period, the new rate’s effect cannot be attributed to 

any particular year. To do so would cause a sudden 

bump in the time series data. In order to smooth out the 

series, the lives saved data for the years 1988 through 

2003 will be recalculated using a wedging procedure to 

gradually introduce the change. Beginning in 1988, the 

number of lives saved is calculated by applying the new 

rate to one-sixteenth of the fatality data and the old rate 

to fifteen-sixteenths of the data. For succeeding years, 

the fractions are incremented and decremented by onesixteenth until the new rate is used for the entire 

calculation in 2003. 

Definitions 

Of course, head injuries are not the only cause of crash 

fatalities. When we speak of “effectiveness” of helmets 

in reducing the risk of death in fatal motorcycle crashes, 

all types of injuries suffered by riders are included by 

implication. For example, if a helmet were absolutely 

certain to prevent a severe head injury, the rider could 

still die from other traumatic injuries suffered in a crash. 

Clearly, motorcycle helmets cannot prevent all fatal 

injuries. Just how effective helmets are in preventing 

fatalities is a function of both their performance in 

crashes and the incidence of fatal injuries other than 

head injuries. 

Fatalities 

In the calculation of lives saved, the definition of a 

fatality is the same as that used in the FARS database, 

that is, any motorcycle operator or passenger who dies 

within 30 days of the crash from injuries directly 

associated with the crash. 

Table 1 - Lives Saved by Motorcycle Helmets In 2003

Fatalities 

Motorcyclists Effectiveness Total Helmeted Unhelmeted 

Lives 

Saved 

Potential 

Lives 

Saved 

Operators 0.37 3,382 1,805 1,577 1,060 1,644 

Passengers 0.41 279 141 138 98 154 

Total 0.37 3,661 1,946 1,715 1,158 1,798 
NHTSA’s National Center for Statistics and Analysis 400 Seventh St, SW, Washington DC 20590

Motorcycles 

Motorcycles are those vehicles described in FARS codes 

80 through 89. These include motorcycles, mopeds, 3-

wheeled cycles other than All-Terrain Vehicles (ATVs); 

“other” motorcycles; and motorcycles of unknown type. 

All of these body types are referred to collectively as 

motorcycles. 

Motorcycle Riders 

Motorcycle occupants, or riders, are either operators or 

passengers. In the FARS codes, motor vehicle occupants 

are composed of drivers, passengers of a motor vehicle 

in transport, or unknown occupants of a motor vehicle in 

transport. In the calculation of motorcycle riders’ lives 

saved, the unknown occupants are distributed 

proportionately between motorcycle operators and 

passengers. 

Helmeted and Unhelmeted 

In calculating lives saved, the FARS variable 

REST_USE, (Restraint Use) is used to determine 

whether or not a motorcycle rider is helmeted. A rider is 

considered to be unhelmeted when coded either as 00 

(None Used/Not Applicable) or 15 (Helmet Used 

Improperly). With the exception of unknowns, which 

were proportionally distributed, all other codes were 

interpreted as helmeted. This includes codes for safety 

belts and child safety seats. The assumption made is that 

the original investigator who filled out the Police 

Accident Report, or PAR, had used a restraint code to 

indicate that a helmet was worn. The number of cases 

that are coded in this manner is quite small, lending 

support to the assumption. 

References 

1. The method was first used at NHTSA in 1988. See: 

Evans, Leonard, and Frick, Michael, “Helmet 

Effectiveness in Preventing Motorcycle Driver and 

Passenger Fatalities: Accident Analysis and 

Prevention,” U.S. Department of Transportation, 

National Highway Traffic Safety Administration, 

Volume 20, Number 6, 1988. 

2. National Center for Statistics and Analysis, Safety 

Belt and Helmet Use in 2002 - Overall Results, 

NHTSA Technical Report DOT HS 809 500. 

3. National Center for Statistics and Analysis, 

Motorcycle Helmet Effectiveness Revisited, NHTSA 

Technical Report DOT HS 809 715. 

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 William Deutermann (202-366-5206). Internet 

users may access this research note and other general 

information on highway traffic safety at 

www-nrd.nhtsa.dot.gov/departments/nrd30/ncsa/AvailInf.html.