The current research aims to determine the relationship between driver inattention and crash risk in lead-vehicle pre-crash scenarios (corresponding to rear-end crashes). It aims to develop inattention-risk relationships describing how an increase in inattention performance variables combines with context in lead-vehicle pre-crash scenarios to increase risk. The inattention-risk relationships are intended to show which glance behaviors are safer than others and pinpoint the most dangerous glances away from the road. A glance is the time from the moment at which the eyes move towards an area of interest (such as the radio, rearview mirror, or forward path) to the moment they move away from it. The results aim to (1) support distraction policy, regulation, guidelines, (2) improve intelligent vehicle safety systems, and (3) teach safe glance behaviors.