Experts point to positive developments to explain these numbers (things like the inclusion of airbags and electronic stability control in more vehicles), but the underlying trend is clear: The first half of the year saw record fuel prices, while the second half saw the beginning of an economic downturn.
This led to a steep decline in the number of miles Americans drove. The Federal Highway Administration estimates the total was 112 billion miles fewer than the previous 13-month period on record. Although there were fewer cars on the road back then, the decline during the oil embargo of the 1970s was only 49.9 billion.
The decrease in miles driven surely had a huge impact on the decline in traffic deaths. Overall, the fatality rate per 100 million miles driven fell from 1.37 in 2007 to 1.28 in 2008, according to the Department of Transportation. The last two months of the year have yet to be calculated, but if they hold to the trend, that would make the fatality rate the lowest since 1966.
Traffic Deaths Down in 42 States (USA Today)