Nationally, 20% to 30% of freeway truck accidents
occur on or near ramps (excluding an additional
10% to 15% that occur at intersections of
ramps and surface streets), despite the fact that
interchanges account for less than 5% of all freeway
lane-miles (Firestine et al 1989). These same
percentages hold true for many western states. Of
nearly 2,400 truck accidents on Colorado freeways
during 1993, 1994, and early 1995, roughly 30%
occurred at interchanges, and another 10% occurred
at intersections with secondary roads. (We
use the term “freeways” in this paper to include all
limited access highways; e.g., interstate highways,
expressways, turnpikes, and parkways.)
Sullivan (1990) found accidents per vehicle-mile
of travel (VMT) to be significantly related to the
number of interchange ramps along California
freeway sections. In an older study of freeway accidents
throughout the United States, Pigman et al
(1981) found accidents occurred 33% more often
per VMT on freeway sections with bridges or
interchanges than on freeway sections without
them (see table 1). Both of these findings were for
accidents of all vehicle types and severity (fatalities,
injuries, and property damage only). However, we
also found that truck accident rates were significantly
higher on freeway sections in the vicinity of
interchanges in our own analysis of truck accident
data reported by Goodell-Grivas (1989).
Truck Accident
Semi Truck Accident
