Based on a disabling-injury to death ratio of 53 to1, the NSC estimates the number of nonfatal disabling injuries that will result from crashes during the holiday period is 27,600.
According to Alan F. Hoskin, who wrote the report for NSC's Statistics Department, "A frequently asked question is 'How much more dangerous is travel over the Independence Day holiday?' There are two aspects of this question that must be considered. First, compared to what? And, second, what about changes in the amount of driving?"
He said the NSC study chose to compare the holiday to periods of similar length (3.25 days). The average number of traffic deaths during the Independence Day holiday weekend is 7.1 percent higher than the average number of traffic deaths during the comparison periods.
The second question, said Hoskin, concerns changes in the amount of travel, or exposure. "We know of no data system that tracks changes in vehicle miles of travel by day of the year on a national basis," he noted. "Lacking an objective measure of exposure change, we assume that travel is greater on holiday weekends than on nonholiday weekends."
If the assumed travel increase exceeds 7.1 percent, then the risk of dying in a traffic crash during the Independence Day holiday period is less than during comparable non-holiday periods, said Hoskin. If the travel increase is less than 7.1 percent or if travel is actually lower, then the risk of dying on the holiday is greater than during comparable periods.