Nevada's Sen. Richard Bryan is a Democrat who has picked a democratic fight, one involving everyone.

His bill would raise CAFE (corporate average fuel economy) standards from the current 27.5 miles per gallon to approximately 34 in 1996 and 40 in 2001. His is a perversely efficient proposal, demonstrating the many vagaries of regulations and the many ways intended improvements can make matters worse.Driving is the most dangerous thing most Americans do. Bryan's bill would make it more so. Furthermore, it probably would have negligible, and perhaps negative, influence on fuel consumption and the environment.

There are two basic means of increasing automobile fuel efficiency. One is technological innovation that improves the burning of fuel and the transmitting of the resultant energy through the vehicle's drivetrain. The other is by making vehicles lighter.

Not even Congress can limitlessly command technological improvements. Today increased fuel mileage depends increasingly on lightening vehicles, frightening for a nation in which about 130 people - casualties comparable to those in an airline crash - die on roads daily.

The reduction of car sizes, and of the ratios of steel to mass, has made the average American car 23 percent lighter than in 1974. In the 1978 model year, 25 percent of new cars weighed more than 4,000 pounds. Only 1 percent of cars built since 1984 do. In 1978, 70 percent of new cars weighed more than 3,500 pounds. By 1988, only 37 percent did.

Robert Crandall of the Brookings Institution and John Graham of the Harvard School of Public Health, both economists, calculate that the 500-pound weight reduction that they ascribe to CAFE standards has increased fatalities over the life of each year's model cars between 14 percent and 27 percent, or 2,200 to 3,900 extra deaths (plus 11,000 to 19,500 additional serious injuries) over the lifetime of each year's vehicles. Crandall estimates that Bryan's proposed 40 mpg standard would require weight and steel-content reductions sufficient to increase CAFE-related deaths to between 4,800 and 8,600 over the life of a model year.

Is there an environmental, and hence public health, benefit commensurate with CAFE costs? Approximately 50 percent of all auto pollutants come from 10 percent of all cars - generally the worst tuned and usually the oldest. If Bryan's CAFE standards become law, new large cars will become much more expensive because manufacturers will raise prices of large cars to subsidize prices and stimulate sales of small cars, to improve their fleet fuel economy average. Large cars will become more scarce - perhaps even extinct. So millions of safety-conscious drivers will keep their old large cars rather than buy new ones, thereby injuring both the air and the autoworkers.