No one likes being rear-ended by an inattentive driver, but help may be on the way. A new study from U of T’s Ergonomics in Teleoperation and Control Laboratory may be able to make people react faster to heavy braking.
By making vehicles appear larger than they really are, industrial and mechanical engineers Zhonghai Li and Dr. Paul Milgram hope to reduce or even eliminate the damage of rear-end collisions.
Li and Milgram study the human factor in human-machine interactions. For his PhD thesis under Milgram, Li (now a post-doctoral student) investigated the effects of manipulating optical looming cues on human braking behaviour. Optical looming cues help us perceive speed and distance, based on how large an image looms in front of us, and guides our response. When a driver approaches a leading car traveling at a slower speed, the image of the car on the driver’s retina will expand at an increasing rate, alerting the driver of a looming collision. Normally, the driver instinctively hits the brakes.
“The study examined the feasibility of reducing rear-end collisions by manipulating what the driver in the following vehicle sees,” said Milgram.
With the help of 40 participant drivers, Li’s study used a driving simulator under different conditions-for example, clear, sunny conditions or stormy, night-time conditions. Since it is impossible to physically change the size of a car should the study’s findings be applied in real life, the next best option was to change the apparent size of the tail lights, which we also use as cues to judge distances. The study found that an expanding triangle of taillights, whose lights spread apart and grow larger with harder breaking and shrinks to a smaller triangle with lighter breaking, prompted the driver to start braking earlier than normal. The largest differences in breaking time were found under low visibility conditions.
“If you change the separation distance of the [brake lights] by spreading them out and making them appear bigger, they will affect the following driver’s braking,” Milgram explained.
“The expansion of the tail lights is imperceptible to following drivers, yet still reduces braking time by 100-300 milliseconds” said Milgram. “That’s a difference of several metres when you’re traveling at 80 km/h.”
Time is a crucial factor in determining the severity of a collision as even a fraction of a second can make a substantial difference. Today’s taillights do not convey any indication of braking intensity. If drivers were aware of the intensity of braking up ahead, they would have more time to respond, potentially preventing rear-end collisions. The researchers hope to interest car manufacturers in brake lights that can move and grow-an idea that may grow on grumpy drivers.
