“…Information that drivers potentially use to detect deceleration (other than brake lights) includes the lead car’s optical expansion pattern, that is, the increase in the visual angle subtended at the driver’s eye by the car being approached (DeLucia & Tharanathan, 2009; Lamble et al, 1999). When the optical expansion rate of a vehicle exceeds a threshold value, between 0.003 and 0.006 radians per second (rad/s), a driver putatively can determine that the relative velocity of the lead vehicle has changed and that it is getting closer (Hoffman & Mortimer, 1996; Muttart, Messerschmidt, & Gillen, 2005).…”