All highway accidents in South Dakota occurring during 2006 and occurring in the vicinity of work-zones were identified. The 367 formal reports filed with the state Department of Transportation by law enforcement officers investigating the accidents were provided to us. We categorized each accident according to the type of road environment involved, the type of accidental contacts between vehicles that occurred, lighting conditions, demographic descriptors of the drivers involved, and a tentative finding of fault. Preliminary reduction of this data pool suggests that males under the age of 25 were over-represented in work-zone accidents, and that drivers over the age of 65 were under-represented, particularly at night. Among 170 accidents involving front-to-rear-end contact we defined a subgroup of 125 that were characterized by Misperceived Closure Rate judgments. 116 such misperceptions took place in daylight or twilight, only 9 in darkness. Drunk driving was associated with only 3 of these accidents.