(FORTUNE Magazine) – Why are newspapers of every coloration sounding off these days on the 55- mile-per-hour speed limit and the lives it is allegedly saving? Well, it seems that a panel of scholars assembled by the National Research Council has produced a statistic-laden report favorable to this limit, so what can the editorial writers do but state whether they agree or disagree, and most of them are nervously agreeing because they do not have any countervailing statistics of their own and besides they wonder if it might be bad P.R. to come out in favor of death. The NRC report is a treasure trove of fascinating facts, estimates, conjectures, and probability distributions on the subject of driving. The report says, as you might have suspected, that compliance has been slipping and average speeds rising in recent years. Despite the speedup, highway fatality rates have been declining rather sharply--from 3.5 per 100 million vehicle miles in 1979 to 2.76 in 1983. The report nevertheless argues, and with some plausibility, that the 55-mph limit is not just irrelevant. Evidence abounds that the limit continues to have some effect on average speeds, and the link between speed and fatalities is clear enough. So we would not dispute the NRC estimate that maybe 2,000 to 4,000 lives per year are being saved by the limit. Missing from the sea of statistics in the report, however, are any facts or probabilisms that would enable a reasonable person like yours truly to decide whether the economic costs of saving those lives are worth the benefits. When you drive slower, you stay out on the highways longer; the report estimates ! that the 55-mph limit is, in fact, keeping the people out there for about one billion hours per year more than they would otherwise be. If we assume 3,000 lives are being saved, we're talking 350,000 hours per life. That is the equivalent of 120 people each driving eight hours a day for a year. What we kept looking for in the NRC report, and not finding, was some formulation about the opportunity cost of all that roadwork. That is, how much wealth could those 120 people be creating in a year if they weren't harnessed to the wheel? The answer can't possibly be less than $1 million (which assumes only $8,000 per person). We intuit that anybody who had $1 million, and wanted to save lives, might contribute to cancer research, or to a fund for putting more cops on the beat, but almost certainly wouldn't regard a massive rearrangement of American driving habits as the most efficient way to forestall termination. Also missing from the report was any explanation of why 55 is the right number. Why not a 45-mile-per-hour limit? Why not 35? Why not find out how much the editorial writers of America really know about P.R.?