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

 Research Note

Revised

U.S. Department

of Transportation

National Highway

Traffic Safety 

Administration February 15, 1996

Crash Outcome Data Evaluation System (CODES) Project

Safety Belt and Helmet Analyses

 Sandy Johnson, Jonathan Walker, Dennis Utter

Analyses of the benefits of safety belt and 10,353 motorcycle riders for the helmet

helmet use were undertaken in response to analyses. 

Section 1031(b) of the Intermodal Surface

Transportation Efficiency Act of 1991 (ISTEA)

for a Report that was sent to Congress

February, 1996. NHTSA awarded grants to

entities in Hawaii, Maine, Missouri, New York,

Pennsylvania, Utah, and Wisconsin to link

crash and injury state data and perform the

analyses upon which the report was based. 

The individual state estimates are reported in

the CODES Technical Report which

describes the linkage and analytical

processes used in the CODES project. injuries is 35 percent, then 35 percent of

Data Collection Methodology

The study employed probabilistic linkage

methods whereby statewide data from police

crash reports, emergency medical services,

hospital emergency departments, hospital

discharge files, claims, and other sources

were linked so that those people injured in

motor vehicle crashes could be followed

through the health care system. Linkage of

population-based state data enabled

information for both the injured and uninjured

to be used to determine the benefits of safety

belts and helmets in motor vehicle crashes. 

It also provided access to financial 

information; inpatient charges (acute care,

rehabilitation, long-term care) and estimates

of actual costs using a charge-to-cost ratio. 

Inpatient charges represent about 60 percent

of the total direct medical expenses. The

remaining 40 percent include physician

charges, emergency room charges, EMS

charges, and other charges. Through the

cooperation of the highway safety and

medical communities, this was the first time

these databases were linked using a

probabilistic computer algorithm. 

The study population consisted of 879,670

drivers for the safety belt analyses and

Outcome Measures

NHTSA measured effectiveness to determine

the benefits of safety belts and helmets. 

Effectiveness is defined as the percentage

reduction in the likelihood of injury or death

for people wearing safety belts or helmets

compared to people not wearing safety belts

or helmets as appropriate. For example, if

the effectiveness of some device in reducing

those people who were injured while not

using the device would not have been injured

had they used it. The effectiveness of safety

belts and helmets was measured using four

outcome measures: 

 1. Died

 2. Died or admitted as an inpatient

 3. Died, admitted as an inpatient, or

transported by EMS/treated in the

emergency department

 4. Any injury (died, inpatient,

transported, or slightly injured)

To measure the effectiveness in reducing

mortality (outcome measure 1), the group of

crash victims (passenger vehicle drivers for

belt effectiveness and all motorcycle riders

for helmets) who died was compared with all

other crash-involved victims.

 

To assess the effectiveness in reducing

morbidity (outcome measure 4), the group

of crash victims experiencing any injury, i.e.,

slightly injured, transported, inpatient, or died,

was compared with those not injured. 

To assess the benefits in reducing injury

severity, the effectiveness for all outcome
National Center for Statistics and Analysis 400 Seventh St., S.W., Washington, D.C. 20590

measures was analyzed (outcome measures all occupants who were injured and required

1-4). inpatient care as the result of a motor vehicle

To provide the input for computing

effectiveness, each CODES grantee was

required to perform a series of regression

analyses on its linked data using the outcome

measures listed above.

To estimate the effect of safety belt and

motorcycle helmet use on medical costs,

costs were limited to total inpatient charges injuries. However, these effectiveness

found on hospital, rehabilitative, and long- estimates may be inflated because of overterm care patient records. reporting of belt use in police crash reports. 

To provide the input for comparing average effectiveness. The estimates adjusted for

charges, each grantee computed average over-reporting of belt use are consistent with

inpatient charges for passenger vehicle results from earlier NHTSA analyses.

drivers and for motorcycle riders. Averages

were calculated based on the victims’ belt or

helmet use and for various payers. 

Contributing Factors in the CODES States

CODES controlled for type of crash,

rural/urban, age, male/female, posted speed

limit, wet/dry, night/day, intersection related,

vehicle type, and seating position in the

safety belt analyses; only helmet use was

included in the helmet analysis because of

the need to prevent cases from being

excluded because of missing data.

Aggregated Results

 

The results were statistically combined by

NHTSA staff from the individual state data

provided by the grantees. To obtain overall

estimates of effectiveness, state estimates

were weighted by the inverse of their

standard errors. For overall estimates of

average charges, each state estimate was

weighted by the number of observations

which contributed to it. 

The results presented in this report reflect

only the data from the seven CODES states,

and the case selection criteria for the safety

belt and motorcycle helmet analyses. They

are not intended to be nationally

representative. In addition, except as noted,

the financial results were based only on data

from the linked inpatient records. These

linked records represent a sub-population of

crash. 

Benefits of Safety Belt Use

The results of the study revealed that safety

belts are highly effective in reducing

morbidity (the occurrence of any injury) and

mortality. They also indicate that safety belts

cause a downward shift in the severity of

Table 1 presents the estimates of safety belt

Table 1.

 Safety Belt Effectiveness by Outcome 

for Crash-Involved Drivers 

 Outcome

Effectiveness Estimates

Belt Use as Belt Use

Reported by Adjusted for

Police Overreporting 

Died 89% 60%

Died or

Inpatient 75% 45%

Died,

Inpatient, or 54% 30%

Transported

Any Injury 52% 20%

The CODES results showed that the average

inpatient charge for unbelted passenger

vehicle drivers admitted to an inpatient facility

as a result of a crash injury was more than 55

percent greater than the average charge for

those who were belted, $13,937 and $9,004,

respectively. Private insurance accounted

for 69 percent of the inpatient charges

compared to 16 percent for public and 15

percent for other sources. In all cases, the

average inpatient charge was greater for

drivers who were unbelted.
National Center for Statistics and Analysis 400 Seventh St., S.W., Washington, D.C. 20590

Table 2.

Average and Total Inpatient Charges

by Source of Payment and Safety Belt Use 

for Crash Involved Drivers in the CODES States

Source of Total

 Payment Charges

Average Charge

Safety Belt Use

Used Not Used

Public $13,322 $18,922 $26,498,675 1

Private $8,581 $14,058 $113,156,421 2

Other $8,180 $10,534 $24,788,922 3

All Sources $9,004 $13,937 $164,444,018

Includes Medicaid, Medicare, etc. 1

Includes Worker’s Compensation 2 

Usually Self Payment 3

Benefits of Helmets

The study results also showed that

motorcycle helmet effectiveness ranged from

9 percent in preventing any kind of injury to

34 percent in preventing a fatality. These

results confirm previous NHTSA estimates. 

Table 3.

Effectiveness of Motorcycle Helmets

by Outcome

for Crash-Involved Motorcycle Riders

in CODES States*

Outcome Measure Effectiveness 

Died 35%

Died or Inpatient 26%

Died, Inpatient, or

Transported 26%

Any Injury 9% 

Brain Injury 67%

*Excludes Utah.

The average inpatient charge for motorcycle

crash victims receiving inpatient care was

$14,377 for those who used helmets, and

$15,578 for those who did not, an 8 percent

increase in charges for those electing to not

wear a helmet. Private insurance sources

accounted for 63 percent of inpatient charges

compared to 23 percent for public and 14

percent for other sources. For the private

and public sources, average inpatient

charges for motorcycle crash victims were 15

percent and 5 percent higher, respectively,

for the unhelmeted.

Table 4.

Average and Total Inpatient Charges

by Source of Payment and Motorcycle Helmet

Use for Crash Involved Motorcycle Riders in the

CODES States*

Source of Total

 Payment Charges

Average Charge

Helmet Use

Used Not Used

Public $23,793 $24,925 $5,364,759 1

Private

Insurance $13,617 $15,687 $14,764,706 2

Other $10,565 $8,913 $3,403,183 3

All Sources $14,377 $15,578 $23,532,648

*Excludes Utah

Includes Medicaid, Medicare, etc. 1

Includes Worker’s Compensation 2

Usually Self Payment 3

Helmets cannot protect the rider from most

types of injuries. But further analysis of the

CODES data, possible because of the linked

medical outcome, showed that motorcycle

helmets are 67 percent effective in

preventing brain injuries. Thus, if all

motorcyclists had been wearing helmets, 67

percent of those unhelmeted motorcyclists

who received inpatient care for a brain injury

would not have sustained the brain injury. In

other words, unhelmeted motorcyclists were

over three times as likely to suffer a brain

injury as were helmeted motorcyclists. 

Examination of the average inpatient charges

revealed that the average charge for inpatient

care for a motorcyclist who sustained a brain

injury is more than twice the average charge

for motorcyclists receiving inpatient care for

other injuries. On average, approximately

$15,000 in inpatient costs would be saved

during the first 12 months for every injured

motorcycle rider not sustaining a brain injury. 

Therefore, if all injured motorcycle riders

wore helmets, fewer victims would incur the

high cost of inpatient care associated with

brain injury. 

Significance
CODES demonstrated that linked, importance is the fact that linkage identified

comparable data could be generated to previously unknown problems with missing

evaluate the benefits of belts and helmets in and inaccurate data. Correcting these

terms of medical and financial outcome. problems for the study improved the quality of

Linkage enabled injury severity to be the data in the permanent files, making the

standardized among the CODES states. The state data (linked or unlinked) even more

linked data represent a permanent data file. valuable for future uses.

Besides the belt and helmet study, these data

were used to generate state-specific

analyses and will continue to be used in the

future. The CODES states learned new

linkage skills that can be applied to the

linkage of other types of records and also can

be shared with other states interested in

linkage. Of even more 

Copies of the CODES Report to Congress on

the Benefits of Safety Belts and Motorcycle

Helmets and the CODES Technical Report

may be obtained from the National Center for

Statistics and Analysis, National Highway

Traffic Safety Administration, 400 7th Street,

SW, Room 6125, Washington, DC 20590 or

send a FAX request to 202-366-7078.

U.S. Department

of Transportation

National Highway 

Traffic Safety 

Administration

400 Seventh Street, S.W. , NRD-31

Washington, D.C. 20590