The two trends, which reverse long-established patterns, are documented in the annual report of the National Center for Health Statistics. The figures, which relate to 1995, show firearms deaths falling from a peak of 15.6 per 100,000 people in 1993 to 13.9 in 1995, an 11 per cent fall. This compares with an increase of 22 per cent between 1985 and 1993. Traffic deaths, in contrast, rose by 2 per cent over the same period to reach 16.4 after falling from 18.4 per 100,000 people in 1985 to 15.4 in 1993.
While the fall in fatal shootings is variously attributed to tougher laws and policing, demographic factors (fewer young men in the age range at highest risk) and changes in public attitudes towards violence, the authorities find the increase in road deaths harder to explain. They discount some of the obvious causes: deaths in alcohol-related accidents have fallen by 32 per cent in the past 10 years, and the nationwide 55mph speed limit was abolished only last year - too recently to affect the 1995 figures.
The Department of Transportation, which compiles its statistics differently, denies that the increase in road deaths is as large as health officials say it is. Its figures for 1996 show deaths up by 109 (out of a total of 41,907) - a figure a spokesman described as "negligible" - and it says the number has remained "unchanged" since 1992.
But the main road safety organisation, the National Highway Traffic Safety Administration, is in little doubt, either about the interpretation of the figures or about the cause. It ascribes the earlier fall in deaths to increased safety consciousness - greater use of seat belts, less drunken driving, improved car engineering and lower speeds. It blames the recent increase on one thing: recklessness on the part of drivers.
After two weeks of driving in five different states, I cannot express great surprise. While the US enjoys an international reputation as a nation not just of car drivers, but of safe car drivers, the statistics tell a different story. In terms of road deaths per 100,000 of the population, its has long been more dangerous than most West European countries, including France and Germany. Britain ranks among the safest.
I am inclined to agree with the road safety organisations in judging that driving standards in the US have markedly declined in recent years. From being a relaxing pleasure, driving the highways and byways of the US has become, at least for the occupants of a small passenger car, an experience fraught with risk.
Whether because the density of traffic has increased or because cars were engineered for the 55mph speed limit (introduced as an energy-saving measure in the wake of the oil crisis), the ability of many US drivers to manoeuvre and react at speed seems minimal compared to that of European drivers.
The vast lorries that ply the interstate motorway system may be subject to tough weight limits, but most states do not regulate their speed or the lanes they travel in. The result is an intimidating presence of heavy vehicles storming along the fast lanes of major routes. It is no wonder that more and more Americans are buying bigger and yet bigger cars.