I'd bet it's that stretch of highway between the two reservoirs about a mile east of Lowell, a long-term chronic scene of accidents, with some very sharp turns going downhill for the vehicles going west. That's an unusually dangerous two miles. It doesn't take sleep, suicide, or alcohol to have an accident there. A couple of the downhill (going west) turns are particularly deceptive, seeming to sharpen after the entry into the curve.