Benefits of Safety Belts

and Motorcycle Helmets

U.S. Department

of Transportation

National Highway

Traffic Safety

Administration

Report to Congress

February 1996

Based on Data from

The Crash Outcome Data Evaluation System

(CODES)

ACKNOWLEDGMENT

The National Center for Statistics and Analysis of the National Highway Traffic

Safety Administration wishes to acknowledge the outstanding collaborative effort by

the many individuals and organizations in the 7 CODES states -- Hawaii, Maine,

Missouri, New York, Pennsylvania, Utah, and Wisconsin -- in generating the data for

and assisting in the preparation of this report.

CODES Report to Congress - i - February 1996

EXECUTIVE SUMMARY

This study was undertaken in response to Section 1031(b) of the Intermodal

Surface Transportation Efficiency Act of 1991 (ISTEA), which required the National

Highway Traffic Safety Administration (NHTSA) to conduct a study to determine the

benefits of safety belt and motorcycle helmet use in crashes. 

The study employed 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. Information for

both the injured and uninjured was then used to determine the benefits of protective

devices in motor vehicle crashes. The available financial information included

inpatient charges (acute care, rehabilitation, long-term care) and estimates of actual

costs using a charge-to-cost ratio. Through the cooperation of the highway safety and

medical communities, this was the first time these databases were linked using a

probabilistic computer algorithm. Grants were awarded to entities in Hawaii, Maine,

Missouri, New York, Pennsylvania, Utah, and Wisconsin to complete the linkage and

perform the analyses upon which this report is based. All of the states were able to

generate the linked data. 

The Crash Outcome Data Evaluation System (CODES) study results 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 injuries. 
CODES Report to Congress - ii - February 1996

The study 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 that were belted,

$13,937 and $9,004 respectively. If, in the CODES states, all unbelted passenger

vehicle drivers had been wearing safety belts, it is estimated that inpatient charges

would have been reduced by approximately $68 million and actual inpatient costs

reduced by $47 million. 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.

The study results also showed that motorcycle helmet effectiveness ranged

from 9 percent in preventing any kind of injury to 35 percent in preventing a fatality. 

These results confirm previous NHTSA estimates. 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.

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
CODES Report to Congress - iii - February 1996

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 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. 

CODES demonstrated that linked, comparable data could be generated to

evaluate the benefits of belts and helmets in terms of medical and financial outcome. 

Linkage enabled injury severity to be standardized among the CODES states. The

linked data represent a permanent data file. 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 importance is the fact that linkage identified previously unknown

problems with missing and inaccurate data. Correcting these problems for the study

improved the quality of the data in the permanent files, making the state data (linked or

unlinked) even more valuable for future uses.
CODES Report to Congress - iv - February 1996
CODES Report to Congress - 1 - February 1996

INTRODUCTION

The Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), required

the Department of Transportation and NHTSA to study the benefits of using safety

belts and motorcycle helmets. This requirement appears in Section 1031, USE OF

SAFETY BELTS AND MOTORCYCLE HELMETS, part (b) STUDY:

"(1) In general. -- The Secretary shall conduct a study or studies to determine

the benefits of safety belt use and motorcycle helmet use for individuals involved

in motor vehicle crashes and motorcycle crashes, collecting and analyzing data

from regional trauma systems regarding differences in the following: The

severity of injuries; acute, rehabilitative and long-term medical costs, including

the sources of reimbursement and the extent to which these sources cover

actual costs; government, employer, and other costs; and mortality and

morbidity outcomes. The study shall cover a representative period after

January 1, 1990."

Funding was made available through the ISTEA, and the legislation called for a

report to be submitted to Congress within "... 40 months after the funds for such a

study were made available...." This report contains the results of that study.
0.2 % Fatalities

CODES Report to Congress - 2 - February 1996

Exhibit 1. Distribution of Persons Involved in Motor Vehicle

Crashes by Injury Outcome

STUDY DESIGN

Population Coverage

In designing the study, NHTSA considered the requirements specified in the

legislation, the types of information which would comply with those specific analytic

requirements, and the availability of such information. Consequently, the study results

presented in this report are based on statewide databases in the participating states

which include all persons involved in police-reported crashes -- those who were injured

or who died and those who were not injured. In this manner, comparisons between

those using and not using safety belts or motorcycle helmets could be made by

identifying and contrasting the characteristics of the injured and uninjured occupants

within each of the use groups. Exhibit 1, generated from previous research (all 1

footnotes are on page 35), shows the approximate distribution of persons involved in

motor vehicle crashes by the severity of injury and emphasizes the fact that the

majority of persons involved in crashes are not injured.
CODES Report to Congress - 3 - February 1996

In an individual state, the comprehensive source of information about all people

involved in motor vehicle traffic crashes (including those involving passenger cars,

vans, light trucks and motorcycles) is the statewide database created from crash

reports filed by police agencies in the state. Police officers, who investigate the crash

at the scene, complete a report which includes information about the crash, the

vehicles, and the persons involved. Selected data from these reports are entered into

an electronic database from which most states produce an annual report describing the

crashes occurring in that state. The availability of these databases in electronic format

make the data readily available for statistical analysis. 

Statewide crash databases have some limitations, however. The individual data

items collected by states vary widely. The training of the police officers in crash

investigation and data collection, the data elements collected by police officers, and the

actual data coded by each state onto its database, are different. Many states include

information about all vehicle drivers and passengers, injured or uninjured, while others

include information for passengers only if they are injured in the crash. Not all motor

vehicle crashes are reported to the police. Every state has a minimum reporting

threshold which excludes some or all of those crashes causing only minor property

damage and no injuries. Thus, there may be even more successes resulting from the

use of safety measures, currently undocumented and unavailable for analysis. Despite

these shortcomings, statewide police-reported motor vehicle crash data are the only

comprehensive source of data on a definable set of crashes within a given state.

Police-reported crash data also are limited in providing information about the

medical and financial outcomes of crash victims. Police officers are not trained
CODES Report to Congress - 4 - February 1996

diagnosticians and, in most states, do not code specific injuries to crash-involved

occupants, nor are they able to obtain information on the financial consequences to the

injured victims. Police crash reports typically contain a field for "injury severity". In

most states the police use a standard scale similar to the "KABC0" scale, where:

K = killed;

A = severe or incapacitating injury;

B = non-incapacitating injury;

C = possible injury; and,

0 = not injured.

The application of this scale depends on a police officer's evaluation at the

scene. Persons with different medical severities are often included within the same

class. Frequently, transport by emergency medical services (EMS) of a crash victim

for treatment is enough for the police officer to code "incapacitating injury." On the

other hand, some injuries are not immediately evident at the scene of a crash, and a

victim who is later diagnosed with a serious injury can be initially classified as not

injured.

Therefore, police-reported crash data alone are not sufficient to satisfy the study

requirement to examine the benefits of safety belts and motorcycle helmets with

respect to "the severity of injuries," the "... medical costs, including the sources of

reimbursement and the extent to which these sources cover actual costs," and "...

government, employer, and other costs." Information to address these requirements

must be found in other data sources.
CODES Report to Congress - 5 - February 1996

Data relating to the type and cost of medical treatment provided to crash victims

could come from several different medical service providers: emergency medical

service (EMS) treatment and transport, hospital emergency department (ED)

treatment, inpatient hospital treatment, nonhospital-based physician services,

rehabilitative/long-term care, etc. Each one of these providers may have its own

system for record keeping and billing. Some of these systems are statewide and some

are limited to the facility or office where the treatment occurs. None of the data

systems, however, are designed to be linked with other systems.

One statewide medical outcome database, a centralized database of inpatient

hospital discharge information, is available in most states. This file usually includes

diagnosis codes, procedure codes, and charges relating to the patient's hospital

confinement. This last item, hospital charges, includes only the institutional

component, not the professional fees, incurred at any of these facilities and does not

represent actual costs. 

The availability at the state level of other medical outcome information for motor

vehicle crash victims is limited. Some states support statewide databases such as

EMS run reports, hospital emergency department records, or rehabilitative and longterm care facility treatment summaries. Not all states collect or build statewide files

from all these sources of information. But where they are available, these databases

and the hospital discharge database are a valuable information source for highway

safety research, particularly when an individual patient record can be associated with

data on a police crash report.
Hospital

Discharge

Rehab/

Long

Term

Care

 Outpatient

Insurance

Claims

Death

Certificate

Traffic Records

CODES Report to Congress - 6 - February 1996

Exhibit 2. Crash and Injury Data Sources

NHTSA, therefore, elected to meet this study's data needs using police-reported

crashes as the study population. The police reports were used to identify crashes,

circumstances about the crashes, the vehicles, and the people involved. Patient

information from the available data sources, usually EMS, ED, hospital discharge, and

long-term and rehabilitative care databases, was used to identify injury outcomes and

charges for those injured. The different databases were linked to obtain populationbased occupant-specific outcome data for injured crash victims. Linking the databases

enabled the information about the injury-causing event (the motor vehicle crash) to be

directly related to specific medical and financial consequences for each person

involved in the crash. This detailed information was used to evaluate the failures and

successes resulting from the use or non-use of safety devices. Exhibit 2 shows

schematically the linking of databases in a state where all such databases are

available.
CODES Report to Congress - 7 - February 1996

Grants

NHTSA elected to fulfill the legislative mandate by providing grants to several

states to link available databases and perform analyses using the linked data. Access

to the needed databases would be obtained by the grantee from the owner agencies. 

The grantee would link the medical outcome databases to the police crash report file. 

NHTSA decided not to fund any states which would need to create new databases and

instead focused on those that could guarantee delivery of the data for the analyses. 

Additionally, to promote cooperation between owners and users of the required

databases, the grants would be made to a single applicant in a state who would be

responsible for obtaining cooperation from the owners of the data.

In a May 5, 1992, Federal Register announcement, NHTSA published a grant

solicitation requesting applications from states. The announcement specified that

applicants should have an available statewide crash report database, computerized

EMS, ED, hospital discharge, and rehabilitative/long-term care databases, and further,

be willing to collaborate with the owners of these databases, link the databases,

perform analyses as specified by NHTSA, and provide NHTSA with the linked data and

results of the analyses. Any state agency, nonprofit organization, or educational

institution capable of setting up a coalition of data owners and users to perform the

linkage was eligible to apply. Any representative period after January 1, 1990, was

allowed, to obtain the most recent data each state had available without unnecessarily

limiting the number of possible applicants. Twenty states responded to the solicitation.

Selection of the grantee states was independent of safety belt and helmet use rates

and current statutes mandating use. NHTSA titled the project “CODES”.
CODES Report to Congress - 8 - February 1996

On September 30, 1992, NHTSA awarded grants to conduct the study to

entities in 7 states: the Departments of Health in Missouri, New York, and

Pennsylvania; the Department of Public Safety in Maine, the Department of

Transportation in Wisconsin; and state university systems in Hawaii and Utah. 

Besides having the needed data, the 7 states had other characteristics useful for this

study. All of the states except Maine had enacted mandatory safety belt use laws. 

During the study period, helmet use laws, at various times adopted by all 7 states,

were in force in 3 states: Missouri, New York, and Pennsylvania. Each state had a

statewide police crash report database and a statewide hospital inpatient discharge

file. All states except Wisconsin had a statewide EMS database. Wisconsin had date

of birth and zip code of residence for drivers and injured passengers on its crash file,

which facilitated linkage, in the absence of EMS data, to the hospital discharge and

insurance claims files. Only Missouri and Utah had access to statewide emergency

department data. New York obtained emergency department data for New York City. 

The other states attempted to obtain information for specific population groups from

insurance claims databases. Hawaii and New York were no-fault insurance states. 

New York had access to statewide vehicle insurance claims information, and Hawaii

had access to statewide health insurance claims information.

To promote collaboration, each grantee formed an advisory committee of the

owners and users of the databases they intended to link. In most of the states, this

was the first time these diverse groups collaborated on highway safety issues. These

advisory committees addressed the problems of data accessibility, confidentiality,

uniformity, and quality. They worked to define potential uses for the data and to set up
CODES Report to Congress - 9 - February 1996

and review research projects whose results were included as part of the grantees' final

reports to NHTSA. In short, these committees worked to coordinate the components

which would promote the use of linked data for supporting injury control in the highway

safety environment for the current study and in the future.

As discussed in the preceding section, states differ in the amount and type of

data collected on police crash reports and coded onto their crash databases. Some of

these differences affect the CODES analyses. Of the CODES states, Missouri and

Wisconsin do not collect or code information about vehicle passengers who were not

injured in the crash. Thus, the safety belt benefit analyses presented in this report

were restricted to drivers. However, a comparison of the results for the belt analyses

for drivers compared to all occupants in the 5 states which had the data found no

significant differences. All of the states were able to generate the linked data. 

Overview of Data Linkage

The CODES grantees linked their available databases using probabilistic

linkage, a computer algorithm which makes use of a combination of indirect identifiers

(age, date of birth, date of event, sex, etc.) and, when available, direct identifiers

(name, unique number, etc.). After completing the linkage, each state had a database

in which crash-involved occupants were linked to the available medical outcome

databases (EMS, emergency department, hospital discharge, and/or

rehabilitative/long-term care). Those occupants reported by the police as not injured

were less likely to be linked to a medical outcome record, while those reported as

having incapacitating injuries were more likely to be linked. Those in the middle (i.e.,
CODES Report to Congress - 10 - February 1996

occupants who were reported with possible or non-incapacitating injuries) had varying

linkage rates, since they were less likely than those with serious injuries to be

transported or treated at an inpatient facility, but very likely to receive outpatient

treatment. Thus, the final linkage rates varied according to the availability of outpatient

or claims data.

The success of the linking process was influenced by 2 factors. First, although

the probabilistic linkage algorithm increased the likelihood of accurate matches, some

databases lacked sufficient information to discriminate among the events and persons

involved. Because of privacy considerations, some of the data systems which collect a

person's name do not code it on their electronic database, and, therefore, it is not

available for linking. Having a victim's name or a common identifying number on each

record enhanced the accuracy and helped to increase the number of matches obtained

from the various files. Second, information about the external cause of injury (Ecodes) was not uniformly collected and coded by the hospitals. Thus, injury records

selected for linkage could not be restricted to only those with an E-code indicating

cause of injury as a motor vehicle crash. E-codes documented in the inpatient record

make it possible to exclude from the linkage those individuals not injured in motor

vehicle crashes. 

Outcome Measures

To estimate the benefits of safety belts and motorcycle helmets with respect to

different categories of injury severity, outcome measures for crash-involved occupants

were established. A precursor to the actual outcome measures was a combined scale
CODES Report to Congress - 11 - February 1996

of "injury severity" and "treatment given" for each person in the linked files. This

preliminary scale was based on information generated from the linked data and is

shown in Exhibit 3 in increasing severity. Each crash-involved motor vehicle occupant

or motorcycle rider was coded into one of the 5 mutually exclusive categories.

Exhibit 3.

Severity/Treatment Definitions Used in the CODES Analysis of

Effectiveness of Safety Belts and Motorcycle Helmets

Severity/

Treatment Definition

 Not Injured Reported by the police either as possible injury or not injured and

did not link to a medical outcome record

 Slightly

 Injured 

Reported by the police as injured (except possible injury) but did

not link to a medical outcome record or as possible injury and

linked to an insurance claim record

 Transported Linked to an EMS and/or Emergency Department record but was

not linked to a hospital inpatient record

 Inpatient Linked to medical outcome record indicating inpatient treatment

(acute, rehabilitative and/or long-term care)

 Died Police-reported killed or linked to a medical outcome record

indicating death within 30 days after the crash as a result of the

crash

The actual outcome measures derived from this scale were:

(1) -- Died;

(2) -- Died or inpatient; 

(3) -- Died, inpatient, or transported;

(4) -- Any injury (Died, inpatient, transported, or slightly injured).

These dichotomous measures permitted the grantees to use logistic regression

models for the analysis.
CODES Report to Congress - 12 - February 1996

The linking of the various databases in the grantee states produced a large

number of crashes which contributed 879,670 passenger vehicle drivers and 10,353

motorcyclists for this study. Exhibit 4 shows the distribution of crash-involved

passenger vehicle drivers and motorcycle riders by the severity/treatment levels listed

in Exhibit 3. The distribution of motorcycle riders is different because motorcycle riders

are more likely than passenger vehicle drivers to be injured in police-reported crashes.

Exhibit 4.

Number of Drivers and Motorcycle Riders Contributing to

the CODES Analysis of Effectiveness of Safety Belts and

Motorcycle Helmets, by Severity/Treatment Levels

Severity/Treatment Levels Passenger Motorcycle

Vehicle Riders

Drivers

 Not Injured 703,319 2,892 

 Slightly Injured 81,353 3,128 

 Transported 78,054 2,378 

 Inpatient 14,599 1,604 

 Died 2,345 351 

 Total 879,670 10,353 

Methodology

To evaluate whether safety belts and motorcycle helmets are beneficial in

reducing mortality, morbidity and injury severity, NHTSA used a measure employed in

many previous studies: effectiveness. Effectiveness is defined as the percentage

reduction in injuries or deaths for people wearing safety belts or helmets compared to

people not wearing safety belts or helmets. For example, if the effectiveness of some
CODES Report to Congress - 13 - February 1996

device in reducing injuries is 35 percent, then 35 percent of those people who were

injured while not using the device would not have been injured had they used it. In the

CODES study, 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 estimate effectiveness in reducing mortality (outcome

measure 1). 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. Finally, to assess the benefits

in reducing injury severity, the effectiveness for all outcome measures was analyzed.

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. The results of each of these analyses were provided

to NHTSA by the grantees as part of their final project reports. 

To estimate the effect of safety belt and motorcycle helmet use on medical

costs, costs were limited to total inpatient charges found on hospital, rehabilitative,

and long-term care patient records. Outpatient and non-medical charges were not

available from the patient medical record nor uniformly available from other sources in

the CODES states. Inpatient charges represent about 60 percent of the total direct

medical expenses. The remaining 40 percent include 25 percent for physician

charges, about 4 percent for emergency room charges, about 1 percent for EMS

charges, and 10 percent for other charges. In addition to the direct medical charges 2

paid by the people who are injured in motor vehicle crashes, there are external costs

which are paid, sometimes by the public, when someone fails to buckle up or wear a

helmet. Information on these costs are not readily available from the patient unit 3
CODES Report to Congress - 14 - February 1996

record. 

To provide the input for comparing average charges, each grantee computed

average inpatient charges for passenger vehicle drivers and for motorcycle riders. 

Averages were calculated based on the victims’ belt or helmet use and for various

payers. The results of each of these analyses also were provided to NHTSA by the

grantees as part of their final project reports. 

The results presented in this report 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. Because these methods of computing

averages are strongly influenced by the number of cases, data from the larger states

(Missouri, New York, Pennsylvania, and Wisconsin) may disproportionately influence

the overall weighted average. However, these methods made it possible to compare

the association between injury level and safety belt/helmet use in each state. For

individual state estimates the reader is referred to the CODES Technical Report which

describes the linkage and analytical processes used in the CODES project.

The reader should note that the overall results presented in this report reflect

only the 7 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 all occupants

who were injured and required inpatient care as the result of a motor vehicle crash. 

Consequently, financial results generated from this population of linked records vary
CODES Report to Congress - 15 - February 1996

from those results generated from a previous study based on all inpatient discharges

with any E-code for a motor vehicle crash from 6 states, only one of which also

participated in the CODES project. 

4

Contributing Risk Factors

Assessing whether or not safety belts and motorcycle helmets are effective in

reducing the occurrences of occupant mortality and morbidity, and in reducing the

severity of injury, is not a simple task. While it would be quite easy to compare the

observed injury rates among drivers using safety belts, real differences in injuryreducing effectiveness can be masked by a multitude of factors, (e.g., driver age and

sex) not directly related to safety belt or motorcycle helmet use themselves. To the

extent possible, contributing risk factors need to be identified and included in the

analysis. Exhibit 5 presents the risk factors which were available in all of the CODES

states. 

Exhibit 5.

Contributing Risk Factors Available for the CODES

 Safety Belt and Motorcycle Helmet Analyses

Factor

Analysis 

Safety Belt Motorcycle

Helmet

Type of Crash Not Used

Rural/Urban

Age

Male/Female

Posted Speed Limit

Wet/Dry
CODES Report to Congress - 16 - February 1996

Night/Day

Intersection

Related

Vehicle Type Not Used

Seating Position Not Used

Failure to control for these risk factors might have led to incorrect estimates of

safety belt or helmet effectiveness. Estimates of effectiveness without these factors

incorporated were generated as part of the CODES analysis. These estimates of

effectiveness with and without risk factors were not significantly different in most of the

states. 

RESULTS -- BENEFITS OF SAFETY BELT USE

Effectiveness

The results of the analyses for the effectiveness of safety belts in preventing

death and injury are summarized in Exhibit 6. 

Exhibit 6.

 Safety Belt Effectiveness by Outcome 

For Crash-Involved Drivers in the CODES States *

 Outcome

Measure

Effectiveness Estimates

Belt Use as Adjusted for

Reported by Overreporting of Belt

Police Use 

Died 89% 60%

Died or Inpatient 75% 45%

Died, Inpatient, or

 Transported 54% 30%
CODES Report to Congress - 17 - February 1996

Any Injury 52% 20%

*Please read the discussion of the safety belt analyses on pages 21-23.

Given involvement in a crash, safety belts are effective both in preventing any

injury and in reducing the likelihood of a fatality. This indicates that, in the 7 CODES

states during the study years, many of those unbelted drivers injured or killed in policereported crashes would not have been injured or killed had they been belted. 

However, because of the likelihood of crash involved vehicle occupants to over-report

their safety belt use, it is believed that the study results using as-reported belt use are

inflated. Consequently, estimates adjusted for expected over-reporting were

developed (see the section beginning on page 21 for a discussion on over-reporting). 

Safety belts also are effective in reducing the severity of injuries, as evidenced by the

effectiveness rates which increased as the severity of the outcome increases. The

information in Exhibit 6 implies that safety belts cause a downward shift in the severity

of injuries sustained by vehicle drivers injured in a crash; that is, wearing safety belts

results in fewer injuries and less severe injuries on average than would be sustained if

the drivers do not wear safety belts.

Cost of Crash Injuries

Average inpatient charges for passenger vehicle drivers are presented in Exhibit

7. The exhibit also shows the average charges adjusted for the likelihood of being

admitted to an inpatient facility, that is, an average charge for all crash-involved belted

and unbelted drivers.
CODES Report to Congress - 18 - February 1996

Exhibit 7.

Average Inpatient Charge by Safety Belt Use for Inpatient and

All Crash-Involved Passenger Vehicle Drivers in the CODES

States

 Group Not Using Belts

Safety Belt Use Increase for

Used Not

Used

Inpatient Victims $9,004 $13,937 55%

All Crash-Involved Drivers $110 $562 408%

The difference in average charges (total charges hide the difference between

the belted and unbelted when far more vehicle occupants use safety belts than do not)

between the belted and unbelted groups indicates that unbelted inpatient drivers

experienced higher charges reflecting more severe injuries and longer lengths of stays. 

The average inpatient charge is 55 percent higher for crash victims needing inpatient

care who did not use their safety belt than for those who did, a savings of almost

$5,000 for each belted inpatient. When total charges are distributed among all crashinvolved drivers, the average charge, although smaller in magnitude, shows an even

larger percentage increase for unbelted drivers due to the increased chance of

inpatient care. The overall average inpatient charge for all crash-involved victims

increased by 408 percent for unbelted drivers.
CODES Report to Congress - 19 - February 1996

Comparison of Charge to Cost

As mentioned earlier, this analysis of the benefits of safety belts was based on

the charge information available from the hospital discharge and other (rehabilitative

and long-term care) inpatient databases. Total charges reported in these databases

are higher than the actual cost to the provider. They include a markup factor

established by each health care provider to ensure the overall viability of the facility by

covering bad debts, cost shifting among the payers, and profit/surplus revenue. The

actual cost of care associated with a specific inpatient stay is very difficult to determine

because actual costs are usually not patient-specific or routinely calculated. 

To provide an order-of-magnitude estimate for costs incurred by motor vehicle

crash victims requiring inpatient care, actual costs were estimated separately for each

state using charge-to-cost ratios based on data that are obtained from statewide

Medicare cost reports . For the CODES states , the ratios for the CODES data 5

collection year range from a low of 1.15 to a high of 1.71. Total charges in these states

were $164.4 million. Using the charge-to-cost ratios results in an estimated total cost

of $114.5 million. Estimated savings were then computed and are shown graphically in

Exhibit 8. If all drivers involved in police-reported crashes had been wearing a safety

belt, the savings could be represented as approximately $68 million in reduced

inpatient charges or $47 million in reduced inpatient costs, both 41 percent reductions.
Safety Belt Use

As Reported All Belted Savings

0

50

100

150

200

Total Charges

Estimated Costs

CODES Report to Congress - 20 - February 1996

Exhibit 8. Estimated Total Inpatient Charges and Costs for All

CODES States: (left) Given the Existing Mix of Belted and

Unbelted Drivers As Reported; (center) If All Drivers Were

Belted; and (right) Resulting Savings.

Charges by Payer Source

Hospitals and rehabilitative and long-term care facilities seek payment for

charges from several sources. Private health insurance companies, including

Worker’s Compensation, are usually the primary source. The taxpayer is another

source of payment through government programs such as Medicare and Medicaid. 

Victims without medical insurance are included in the other category. These "selfpayers" often are unable to pay their bills, and the cost of providing this care is passed

on through higher charges for those who do pay. Exhibit 9 shows the total amount of

charges by each payer source and average inpatient charges by type of payer and

safety belt use.
CODES Report to Congress - 21 - February 1996

Exhibit 9.

Average Inpatient Charge and Total Inpatient Charges

by Source of Payment and Safety Belt Use 

for Crash-Involved Drivers in the CODES States

Source of Total

 Payment Inpatient

Average Inpatient Charge

Charges

Safety Belt Use

Difference Used Not

Used

Public $13,322 $18,922 $5,600 $26,498,675 1

Private Insurance $8,581 $14,058 $5,477 $113,156,421 2

Other $8,180 $10,534 $2,354 $24,788,922 3

Includes all charges to Government Funded Sources including Medicaid, Medicare, etc. 1

Private Insurance Companies including Worker’s Compensation 2

Usually Self Payment 3

At the time of discharge, private insurance, including Worker’s Compensation,

was the payer for 69 percent of all inpatient charges. Public sources, usually Medicare

and Medicaid, and other government sources , accounted for 16 percent. The balance

(15 percent) was in the other group. Regardless of pay source, the average charge for

an inpatient who was not using a safety belt was higher than the charge for a belted

inpatient. The average charge for unbelted drivers in the private insurance payer group

was 64 percent higher than for those drivers using safety belts. For those not wearing

safety belts in the public payer group the average charge was 42 percent higher than

for the belted public payer group. For the other group, the difference was 29 percent. 

Note that the most severely injured people who become medically needy can apply for

Medicaid as a result of their injuries. Therefore, the reader is cautioned not to draw

any unwarranted inferences about higher charges to public payers, a subject that was

not studied in this project.
CODES Report to Congress - 22 - February 1996

Discussion of Safety Belt Analyses

 NHTSA has completed many analyses of the effectiveness of safety belts. 

Based on these studies NHTSA believes that the effectiveness of safety belts is in the

range of 40-50 percent for preventing mortality and in the range of 45-55 percent for

preventing morbidity . These estimates are not entirely consistent with those produced 6

from the CODES analyses, and NHTSA believes that the CODES results may be

inflated by over-reporting of belt use on the police crash reports. For most persons

involved in crashes, belt use is self-reported. That is, the police do not observe it. 

During the past 10 years while safety belt laws have been put into force, there has

been an increased tendency toward belt over-reporting, i.e., occupants tell the police

officer they were belted when they were not. Over-reporting may be due to the

presence of legal penalties for non-use of safety belts, to discounts offered by some

automobile insurance companies for a signed commitment that the policy holder will

always use his or her safety belt, or to other reasons. NHTSA's estimates of 40-50

percent for preventing mortality and 45-55 percent for preventing morbidity were based

on data obtained prior to efforts to increase belt use through the passage of belt use

laws and insurance incentives which are believed to have contributed to corresponding

increases in observed belt use. Therefore, they are not as likely to be inflated by overreporting.

Belt use rates are higher for drivers in police-reported crashes used in the

CODES analysis than for drivers observed in the general motoring public. Exhibit 10

shows reported belt use, averaged from data for all of the CODES states, for the

different levels of police-reported severity. These data were the most current at the

time of the study: 1990 in Hawaii and Missouri, 1991 in Maine, Pennsylvania, Utah

and Wisconsin, and 1992 in New York. For comparison, the estimated national use
Police Reported Injury Severity

None PossibleNonincapacitaing Severe Fatal

0

20

40

60

80

100

CODES Report to Congress - 23 - February 1996

Exhibit 10. Police-Reported Belt Use, by Injury Severity for CrashInvolved Drivers in the CODES States. The horizontal line

at 51 percent is the average from NHTSA's '19 Cities

Survey.' 

rate for 1991 based on observational data from NHTSA's 19 Cities Survey was 51

percent. It is unlikely that crash-involved drivers would have higher safety belt use

rates than the general motoring public, since behavior that leads to increased risk of

crash involvement is associated with risks such as driving after drinking or not wearing

safety belts. The effect of higher reported safety belt use, especially among the less

seriously injured and uninjured vehicle drivers, is to make safety belts appear more

effective than they actually are. 

Comparison of the observed and reported belt use rates for the CODES states

suggests that 35 percent of the belted who are uninjured or slightly injured may have
CODES Report to Congress - 24 - February 1996

misreported their belt use at the time of the crash. When this over-reporting rate is

factored into the analyses, the effectiveness rates are closer to 60 percent for

preventing mortality and 25 - 45 percent for preventing morbidity, estimates much

closer to NHTSA's current estimates of belt effectiveness.

For the average inpatient charges reported in Exhibit 7, it is possible to assume

that an injury severe enough to require inpatient care may be more likely to provide

tangible evidence of belt use or non-use, thus discouraging the tendency to overreport. Therefore, the 55 percent figure would stay approximately the same.

For the average charges for the group of all crash-involved drivers, the situation

is much more complicated, because all drivers were included. Assuming a 10 percent

over-reporting by the inpatient drivers, and a 35 percent over-reporting by non-inpatient

drivers, then the percent cost benefit of wearing a belt for crash-involved drivers

approaches the same for drivers receiving inpatient care, or 60-70 percent.

RESULTS -- BENEFITS OF MOTORCYCLE HELMET USE

Effectiveness

In the analysis for helmet effectiveness, NHTSA used data from six of the 7

states for which data were available. Utah was excluded because there was no place

on their police crash report to identify an unhelmeted motorcyclist -- all records were

coded either "helmet worn" or "unknown." Also, all risk factors except helmet use were

excluded to avoid reducing the sample size excessively due to missing data. In the
CODES Report to Congress - 25 - February 1996

safety-belt analyses, dropping all the risk factors except safety-belt use had no

significant effect on the results. In the helmet analyses, if only cases with no missing

data for all risk factors were used, the results would have been extremely unstable due

to the small number of cases. The combined results for motorcycle helmet

effectiveness are summarized in Exhibit 11.

Exhibit 11.

Effectiveness of Motorcycle Helmets by Outcome

Measure

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% 

*Excludes Utah.

Given involvement in a crash, CODES results show that motorcycle helmets are 

35 percent effective in preventing fatality, but only 9 percent effective in preventing any

injury. Effectiveness of motorcycle helmets was higher for more severe injuries, the

same pattern that was found for safety belts. However, motorcycle helmets were not

designed to prevent injuries other than head injuries.

Cost of Crash Injuries to Motorcycle Riders

An analysis similar to the one described previously for safety belts was done to

determine the benefits of motorcycle helmets with respect to charges incurred by
CODES Report to Congress - 26 - February 1996

those injured. Again, the analysis has been restricted to the charge information

available from the inpatient databases. A summary of these results is presented in

Exhibit 12. 

Exhibit 12.

Average Inpatient Charge by Motorcycle Helmet Use

For Inpatient Victims and All Crash-Involved 

Motorcycle Riders in CODES States*

Group Use for Not

Motorcycle Helmet Increase

Wearing

Helmet Used Not Used

Inpatient Victims $14,377 $15,578 8% 

All Crash Involved $2,064 $2,808 36% 

Riders

*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 ($1,201) in charges for those electing to not wear a helmet. When

adjusted for all crash-involved motorcycle riders, the difference in the average inpatient

charge, $744, is 36 percent higher for those not wearing a helmet. These differences

are not as dramatic as those seen for safety belts. This is likely to be an effect of both

the smaller sample sizes involved and the likelihood that motorcycle riders will be

injured in a crash, regardless of whether or not they are wearing a helmet, in large part

because there is little or no protective vehicle structure. 

Comparison of Charge to Cost
Motorcycle Helmet Use 

As Reported All Helmeted Savings

0

5

10

15

20

25

30

Total Charges

Estimated Costs

CODES Report to Congress - 27 - February 1996

Exhibit 13. Estimated Total Inpatient Charges and Costs for 6 CODES

States (Excluding Utah): (left) Given the Existing Mix of

Helmeted and Unhelmeted Riders As Reported; (center) If

All Riders Were Helmeted; and (right) Resulting Savings.

The same charge-to-cost ratios by state as used in the safety belt analysis were

applied to the data from the 6 states which contributed to the motorcycle helmet

analysis. If all motorcycle riders involved in police-reported motorcycle crashes had

been wearing a motorcycle helmet, about 3 percent of total inpatient charges or 7

percent of actual costs would have been saved. This result is shown graphically in

Exhibit 13.

Charges by Payer Source

Exhibit 14 presents the average inpatient charge by type of payer and

motorcycle helmet use for inpatient motorcycle crash victims. 
CODES Report to Congress - 28 - February 1996

Exhibit 14.

Average Inpatient Charge and Total Inpatient Charges

by Source of Payment and Motorcycle Helmet Use

for Crash-Involved Motorcycle Riders in CODES States*

Source of Total

 Payment Inpatient

Average Inpatient Charge

Charges

Motorcycle Helmet

Use Difference

Used Not

Used

Public $23,793 $24,925 $1,132 $5,364,759 1

Private Insurance $13,617 $15,687 $2,070 $14,764,706 2

Other $10,565 $8,913 ($1,653) $3,403,183 3

*Excludes Utah.

Includes All Charges to Government Funded Sources including Medicaid, Medicare, etc. 1

Private Insurance Companies and Worker’s Compensation 2

Usually Self Payment 3

The motorcycle helmet results are similar to those shown for the safety belt

analysis except for the other category. At the time of discharge, the expected pay

source for a majority of charges was a private insurance company. Billings to private

insurance companies covered 63 percent of all charges, and the average charge for an

unhelmeted motorcyclist was almost 15 percent higher than the charge for a helmeted

rider in this group. On the other hand, the average charge for an unhelmeted

motorcycle occupant in the other payer group was lower than for helmeted riders. 

Public sector sources covered about 23 percent of the inpatient charges for

motorcycle crash victims in the 6 states in this analysis. The average inpatient charge

for those injured motorcyclists who used a public payer source was more than 5

percent higher for motorcyclists who did not wear a helmet than for those who did.
CODES Report to Congress - 29 - February 1996

Prevention of Brain Injury

Helmets were not designed to protect the rider from most types of injuries which

could affect a motorcycle rider. Their main function is to reduce injuries to the head

and, especially, the brain. Brain injury is more likely to result in expensive and longlasting treatment, sometimes resulting in lifelong disability, whereas other head injuries,

concussions and skull fractures (without damage to the brain itself), are more likely to

result in full recovery. To examine whether motorcycle helmets would be more

effective in reducing the injuries they were designed to prevent, NHTSA performed a

separate analysis restricting the outcome measure to whether or not the motorcyclist

received inpatient care for a brain injury. One state, Wisconsin, had subdivided its

inpatients with head injuries into brain injury, concussion, and simple skull fracture

groups. The inpatient files from 5 other states were added to Wisconsin's data

following the definitions used by Wisconsin. Again, Utah was not used since the crash

report did not include a code for not wearing a helmet. The model was revised to

include only helmet use as a risk factor to maximize the number of cases which could

be included in the analysis.

The resulting analysis of effectiveness revealed 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. 

Average charges for inpatient motorcycle riders by brain injury status and

helmet use are shown in Exhibit 15. 
CODES Report to Congress - 30 - February 1996

Exhibit 15.

Average Inpatient Charge

by Motorcycle Helmet Use and Brain Injury Status

For Inpatient Motorcycle Riders in CODES States*

Group/

Payer

Source

Motorcycle Helmet Use 

Used Not Used

Brain Not Brain Not

Injured Brain Injured Brain

Injured Injured

All Inpatient Victims $26,985 $12,736 $26,805 $11,730

 Public $33,764 $22,066 $46,347 $11,596

 Private $29,610 $11,834 $24,461 $12,807

 Other $16,664 $9,585 $10,238 $8,593

*Excludes Utah.

Regardless of helmet use and payer source, 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. Inpatient charges for

unhelmeted motorcyclists receiving care for a brain injury ($26,805) are 21⁄4 times

greater than the average charge for care for unhelmeted inpatient motorcyclists not

sustaining a brain injury ($11,730). Therefore, if all motorcyclists wore helmets,

approximately $15,000 in inpatient charges would be saved during the first 12 months

for every motorcycle rider who, due to wearing the helmet, did not sustain a brain

injury. Additional savings would accrue from avoiding the continual costs for care over

a lifetime. 

Discussion of Motorcycle Helmet Analysis

Regarding the effectiveness of motorcycle helmets in reducing fatalities and
CODES Report to Congress - 31 - February 1996

injuries, the results are also consistent with previous analyses NHTSA has conducted. 

The 34 percent figure in Exhibit 11 is very close to a 1989 NHTSA analysis which 7

estimated that motorcycle helmets were 29 percent effective against fatal injury. The

minimal effectiveness of helmets when lesser injuries are added to the analysis should

not be surprising. Helmets prevent head injury, not all injuries.

This makes the analysis of brain injury all the more important, because it shows

that helmets are effective in reducing the types of injury they were designed to reduce. 

They were 67 percent effective in the 6 selected states, which is more than twice the

fatality effectiveness. Helmets also reduce the cost where it counts. In these 6 states,

cases with brain injury were more than twice as costly as non-brain injury during the

first 12 months. 

With motorcycle helmets, the over-reporting problem does not exist, because it

is easier to see "helmet use" than "belt use." There is no substantial group of

motorcyclists claiming they were wearing helmets when they were not. No

adjustments need be contemplated as in the safety-belt analysis. However, there is a

problem with missing data on motorcycle helmet use. New York, with a helmet-use

law, showed "unknown helmet use" on 38 percent of its motorcyclist records. 

Wisconsin, without a helmet-use law, showed only 9 percent. In general, states with

laws are more likely to have missing data. Police may be reluctant to give a ticket for

not wearing a helmet to a motorcyclist who has just suffered a crash.
CODES Report to Congress - 32 - February 1996

CONCLUSIONS

Study Results

The CODES study results confirm earlier NHTSA analyses that safety belts are

highly effective in preventing injury and fatality in motor vehicle traffic crashes, and 

that they cause a downward shift in the severity of injuries. The earlier NHTSA studies

estimated that safety belts are 40 - 50 percent effective in preventing mortality and 45 -

55 percent effective in preventing morbidity. 

The CODES results also show that the average inpatient charge for a driver

admitted to an inpatient facility as a result of a motor vehicle injury is 55 percent higher

if that person was unbelted. For the 7 states contributing data for this study, the

average charge for a belted crash-involved driver receiving inpatient care was $9,004,

while the average charge for an unbelted driver was $13,937. If, in these states, all

unbelted passenger vehicle drivers had been wearing safety belts, it is estimated that

the reduction in inpatient charges would have been approximately $68 million, or an

estimated $47 million in actual inpatient costs. 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.

The study results confirmed NHTSA's estimate of motorcycle helmet

effectiveness (29 percent) in preventing fatalities. CODES results showed that

helmets were 35 percent effective in preventing a fatality. The average inpatient

charge for motorcycle crash victims was $14,377 for those who used helmets, and 

$15,578 for those who did not, an 8 percent increase for those electing not to wear a
CODES Report to Congress - 33 - February 1996

helmet. Seven percent in actual inpatient costs, and more in lifetime care, would be

saved if unhelmeted motorcyclists wore helmets. Private insurance sources

accounted for 63 percent of inpatient charges compared to 23 percent for public and 14

percent for other sources. For both the private and public sources, average inpatient

charges for motorcycle crash victims were greater for the unhelmeted.

Helmets cannot protect the rider from most types of injuries. However, further

analysis revealed that motorcycle helmets are 67 percent effective in preventing brain

injuries. 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 who did not also sustain a brain injury. 

Therefore, if all motorcycle riders wore helmets, fewer victims would incur the high cost

of inpatient care associated with brain injury. 

Significance of CODES

The linked data provide unique insights into the financial outcome of highway

crashes. Police crash reports provide information about the crash environment and

driver/occupants; EMS reports and hospital discharge data add medical information

about injury type and severity; and hospital discharge and insurance claims data reveal

the financial consequences. Taken together, these linked data generated greater
CODES Report to Congress - 34 - February 1996

value than when considered alone. 

Hundreds of thousands of police-reported crashes were included in the

statewide linked data. This large volume of vehicle-related information increases

the available statistical power to discriminate among specific vehicle attributes while

controlling for nonvehicle-related factors making it possible to generate cost benefit

analyses of vehicle safety performance standards. 

An important concern of the public health community relates to the availability

of medical services and their impact on outcome. The availability of linked injury and

crash information supports collaboration between the nonmedical and medical

communities. These data can be used to demonstrate the effectiveness of the

emergency response by police, EMS, and the acute care system, and to predict the

need for an aggressive medical response when specific crash, vehicle, and behavioral

characteristics exist.

 NHTSA often examines state data to evaluate the benefits of specific traffic

safety countermeasures. CODES linked data allow the agency to examine not only a

more accurate description of injury consequences, but also the public health cost

savings associated with highway safety initiatives. Since a high percentage of these

costs are funded by citizens through increased taxes to cover the expenses of

uninsured and underinsured crash victims, documentation of the costs is important to

motivate public and legislative support for stricter laws and enforcement actions. 

CODES provides documentation, generated from a state's own linked data, that is

more credible among local decision makers who may be tempted to repeal the safety

mandates, such as helmet legislation. CODES information has the capability to
CODES Report to Congress - 35 - February 1996

demonstrate the increased costs associated with head injuries for unhelmeted riders,

to identify the health care costs for specific vehicles, crashes, and behaviors (e.g.,

alcohol involvement, unsafe driving actions), to generate community-based information

to support community-based traffic safety programs, and to target specific populations

at risk at the local, regional, or state levels. All of this information identifies and

supports outcome-based injury control activities that have the most potential for

reducing health care costs.
CODES Report to Congress - 36 - February 1996

1. Sensitivity Index Demonstration Project--Final Report. Johnson, S. W. And

VanSciver, E. Washington, DC: National Association of Governors’ Highway Safety

Representatives, 1991.

2. Dorothy P. Rice, Ellen J. MacKenzie, and Associates. Cost of Injury in the United

States. A Report to Congress 1989. The Johns Hopkins University, 1989.

3. Testimony of Ted Miller before House Subcommittee on Surface Transportation,

March 3, 1994.

4. Harris, Joan A. Source of Payment for the Medical Cost of Motor Vehicle Injuries in

the United States. DOT HS 807 800 National Technical Information Service,

Springfield, Virginia, 1992.

5. Almanac of Hospital Financial and Operating Indicators. Cleverley, William O. 

Center for Health Care Industry Studies, Ohio State University (published annually).

6. Final Regulatory Analysis, Amendment to FMVSS No.208, Passenger Car Front

Seat Occupant Protection. DOT, NHTSA, Office of Plans and Policy, July, 1984. 

7. The Effectiveness of Motorcycle Helmets in Preventing Fatalities. Wilson, D. DOT

HS 807 416, NHTSA Technical Report, March, 1989.

FOOTNOTES
DOT HS 808 347

NRD-31

2/96