Utah laws regulating motorcycle driving appear summarized in the American Automobile Association's "Digest of Motor Laws, 1990."

- Special driving rules: Riding two abreast allowed within one lane; riding between lanes prohibited.- Required equipment: Eye protection and safety helmet, required under 18 years of age, one rear-view mirror required on the left side.

- Driver's license: Required; valid for 4 years; expires on licensee's birthday.

- Daytime headlight: While operating a motorcycle during daylight hours, the use of a headlight is not required.

Researchers reporting in one of the most prestigious medical journals, "Journal of the American Medical Association," Nov. 14, 1990, found that head-injury-related death rates of motorcyclists in states without comprehensive helmet use are nearly double those of states with helmet laws that apply to all motorcycle riders.

A study of death certificate data from the National Center for Health Statistics discloses that 53 percent of the people who died in motorcycle crashes between 1979 and 1986 died of head-injury-related causes. Head-injury death rates varied considerably by age, sex and race, the researchers indicated, peaking at 21 years of age, with the highest rate among 21-year-old white males.

Motorcycle death rates in states with partial helmet-use laws that apply to only young riders or passengers were 67 percent higher than in states with laws that apply to all riders, and states with no law had motorcycle death rates that were 50 percent higher.

The relative difference in death rates between states with full laws and those with partial or no laws was even greater for deaths associated with head injury. The death rate associated with head injury in states with partial or no helmet laws was about twice as high as in states with full helmet-use laws.

In South Carolina and Wyoming, where legislators weakened helmet-use laws during the study period, motorcycle head-injury-related deaths rose 184 percent and 73 percent. In Louisiana, where the helmet-use law was strengthened from partial to universal application, the researchers found a 44 percent decline in the head-injury death rate. In Indiana, where there was no law at the outset but a partial law was later adopted, head injury deaths rose 15 percent.

The researchers concluded: "Since helmet reduce the severity of nonfatal head injuries in addition to lowering the rate of fatal injuries, we urge the adoption and enforcement of comprehensive motorcycle helmet-use legislation."

This synopsis of the Journal of the American Medical Association's article is adapted from the Insurance Institute for Highway Safety, Status Report, March 16, 1991.

A very interesting attitude among some motorcyclists was cited in the article: "Most injured motorcyclists who do not wear helmets report that they did not expect to be injured, yet 40 percent of the head-injury-related deaths were ascribed to the motorcyclist's loss of control, not, apparently, to some action of the driver of the other motor vehicle."

- Alton Thygerson is a professor of health sciences at Brigham Young University.