Number 346 May 2008

Traffic Safety Facts

Traffic Tech – Technology Transfer Series

U.S. Department of Transportation 1200 New Jersey Avenue SE., Washington, DC 20590

National Highway Traffic Safety Administration

Evaluation of the Reinstatement of the 

 Motorcycle Helmet Law in Louisiana

Louisiana first adopted a motorcycle helmet law applicable to all riders in 1968. That law was amended in

1976 to require helmet use only by riders under the age

of 18. Then, in 1982, Louisiana reenacted a universal

helmet law, but amended that law in August 1999 to

require helmet use only by motorcyclists under the age

of 18 and riders over the age of 18 who did not have a

minimum of $10,000 in medical insurance coverage.

InAugust 2004Louisiana reinstateditsuniversalhelmet

law. This reinstatement required all motorcyclists, riders and passengers, to wear helmets all the time. Preusser Research Group evaluated the reinstatement of

Louisiana’s helmet law for NHTSA. This study examined rates of motorcycle helmet use, fatalities, and injuries following reinstatement of the motorcycle helmet

law in August 2004.

Helmet Use and Observational Surveys

When the State of Louisiana was under the universal

helmet law (years including 1997, 1998, 1999, 2005, and

2006) virtually all riders were compliant with the law

and wore helmets. However, during the years that the

Louisiana helmet law was repealed, (years including

2000, 2001, 2002, 2003, and 2004), helmet use declined

to around 50 percent, similar to trends observed in

other States.

Crash Data

There was a consistent increase in the number of motorcycle crashes in Louisiana from 1999 to 2005. Statewide,

the number of motorcycles in crashes in 1999 (n=957)

approximately doubled in 2005 (n=1,877).

Motorcycle crashes during the pre-law period (January

1, 1999, to August 14, 2004) were compared to motorcycle crashes during the post-law period (August 15, 2004,

to August 24, 2005). Only data from prior to August 25,

2005, was included in the analyses as a result of the devastation caused by Hurricane Katrina. Helmet use by

crash-involved motorcyclists before the reinstatement

was 42 percent (n=3,218). After the reinstatement of the

law, helmet use rose to 87 percent (n=1,390).

Motorcycle Crashes Pre- and Post-Law Reinstatement for Louisiana, January 1999–August 2005

Pre-Law 

(January 1,1999–

August 14, 2004) % (n)

Post-Law 

(August 15, 2004–

August 24, 2005) % (n)

Helmet Use (Yes) 42.3% (3,218) 87.0% (1,390)

Injury Status

Fatal 5.0% (377) 4.4% (81)

Severe 9.4% (713) 7.2% (133)

Moderate 38.0% (2,894) 34.7% (645)

Complaint 32.1% (2,445) 34.9% (649)

None 15.6% (1,185) 18.9% (352)

Source: Louisiana State University

Multiple logistic regression analyses were conducted

to compare helmet use and injury levels before the law

change to after the law change. The analyses showed

no significant effects of gender or race. The logistic

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

% Helmeted

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Year

Observed Helmet Use in Louisiana, 1997-2006

*Shaded area represents the lack of a universal helmet law.

Source: Louisiana State University
regression showed a strong positive effect of helmet

use post-law reinstatement. The odds of wearing a helmet in a crash after the law was reinstated were 11.7

times greater compared to wearing a helmet during the

pre-law time period. Injuries were significantly lower

in the post-law period compared to the pre-law period

after adjusting for age, gender, and race. Fatalities were

30 percent less likely post-law as compared to pre-law.

There were similar findings for severe injuries and

moderate injuries.

Previous studies of motorcycle helmet laws have used

registrations as a proxy measure for exposure. Reliable

registration data from Louisiana was unavailable to

use in the analysis. However, there was a trend toward

increasing registrations as reported by R. L. Polk and

Company. In the year following reinstatement of the

law, the number of fatal and serious injury motorcycle

crashes declined. Thus there was a decline in severity

despite rising exposure that followed reinstatement of

the motorcycle helmet law in Louisiana.

Another way to consider the impact of helmet usage

after the reinstatement of the universal helmet law is to

calculate the number of fatal and serious injuries as a

proportion of all motorcycle crashes (fatal crashes, serious injuries, moderate injuries, complaint of injury, and

property damage only). This proportion is independent

of changes in exposure. The following figure shows

that the proportion of monthly fatal and serious injury

motorcycle crashes declined after the helmet law was

reinstated, when all motorcycle crashes are considered.

FARS Data

There were a total of 523 fatal crashes in Louisiana from

1996 through2005 inwhichatleastonemotorcycleoccupant was killed for each crash. Kentucky was chosen as

a comparison State to explore possible regional effects

and because its universal helmet law was repealed in

1998. Kentucky had less than a hundred fewer fatal

crashes (N=436) between 1996 and 2005 than Louisiana

(N=523).

In 2004, following the law change there was the first

decrease in crashes in Louisiana since the 1999 repeal.

There was a slight increase in crashes in 2005 but there

were still fewer crashes than before the law was reinstated. Kentucky, during the same time period, also

showed a general increase in crashes. There was a

major shift in Kentucky’s crashes in 1999 perhaps due

to its repeal of its universal helmet law in 1998. After a

decline in 2002, Kentucky’s crashes increased steadily.

It appears that the drop in fatal crashes in Louisiana

was not replicated in a nearby State, and is therefore

likely attributable to the law change.

Proportion of Fatal and Serious Injuries to All Motorcycle Crashes Before and After the Law Change in 

Louisiana, January 1999–August 2005

Source: Louisiana State University

0

0.05

0.1

0.15

0.2

0.25

Jan-99

Mar-99

May-99

Jul-99

Sep-99

Nov-99

Jan-00

Mar-00

May-00

Jul-00

Sep-00

Nov-00

Jan-01

Mar-01

May-01

Jul-01

Sep-01

Nov-01

Jan-02

Mar-02

May-02

Jul-02

Sep-02

Nov-02

Jan-03

Mar-03

May-03May-03

Sep-03

Nov-03

Jan-04

Mar-04

May-04

Jul-04

Sep-04

Nov-04

Jan-05

Mar-05

May-05

Jul-05

Crashes in Louisiana and Kentucky with a Fatally 

Injured Motorcycle Occupant.

Source: FARS (1996–2005)

0

10

20

30

40

50

60

70

80

90

N Crashes

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Year

Louisiana

Kentucky
Conclusion

The 1999 helmet law repeal in Louisiana dramatically

decreased observed helmet use from almost 100-percent compliance to approximately 50 percent. Observed

helmet use doubled upon reinstatement of the universal helmet law in August 2004.

The years following the repeal showed a sharp increase

in the number of motorcyclist fatalities in Louisiana.

Crash data showed that the odds of wearing a helmet

in a crash after the Louisiana motorcycle helmet law

was reinstated were more than double compared to

pre-law. This increase in helmet use after the reinstatement of the universal helmet law by crash-involved

riders was associated with a significantly lower proportion of fatalities, severe injuries, and moderate injuries during the post-reinstatement period compared to

the pre-law period. The analyses indicated that there

were also fewer severe and fatal crashes following the

law change.

Louisiana experienced the first decline in motorcyclist

fatalities in six years when the universal helmet law

was reinstated. These results support the supposition

that the decrease in fatal motorcycle crashes in Louisiana after the helmet law was reinstated was directly

affected by the law change. Time series analysis suggested that there were approximately 9.4 fewer fatal

and serious-injury crashes per month.

Nationally, there is a relationship between the passage

and repeals of helmet laws and the number of motorcycle registrations. Motorcycle registrations have been

increasing since 1997, coincident with the repeal of universal helmet laws in some States. When a greater proportion of the population was not covered by the laws

in their States, motorcycle registrations also increased.

This relationship has been used as an explanation for

rising fatalities after repealing helmet laws. Further

analysis suggests that regardless of this trend, the lack

of a universal helmet requirement leads to increased

motorcycle fatalities well beyond what might be

expected from an increase in registrations.

How to Order

To order Evaluation of the Reinstatement of the Motorcycle 

Helmet Law in Louisiana (29 pages plus appendices), prepared by Preusser Research Group, write to NHTSA,

NTI-111, 1200 New Jersey Avenue SE., Washington, DC

20590, fax 202-366-7096, or download from www.nhtsa.

dot.gov. Patty Ellison-Potter, Ph.D., was the Contracting Officer’s Technical Representative for this project.

TRAFFIC TECH is a publication to disseminate information about

traffic safety programs, including evaluations, innovative programs, and new publications. Feel free to copy it as you wish. If you

would like to receive a copy, contact Patricia Ellison-Potter, Ph.D.,

Editor, fax 202-366-7096, e-mail: traffic.tech@dot.gov.

1200	New	Jersey	Avenue	SE.,	NTI-130

Washington,	DC	20590