The problem is particularly acute in states like Michigan, Virginia and Pennsylvania, where densely populated urban areas quickly give way to rural landscapes. In those settings, both cars and deer are plentiful and they cross paths frequently, often when cars are traveling at 50 miles per hour on winding and woodsy roads.
Volvo, the Swedish automaker, started equipping several 2017 models, like its XC90 sport utility vehicle, with software that allows its forward-looking radar and cameras to identify large deer entering or crossing a roadway.
“The radar detects if there’s an object and the camera confirms it is a deer by comparing what it sees to thousands of images of large animals,” said Jim Nichols, a Volvo spokesman. “If there’s a match, it gives the driver a warning. If no action is taken, the car automatically slows or stops.”
Audi will introduce a new A8 sedan this summer with radar and other sensors that should stop the car from hitting large animals if they are standing in the roadway.
Toyota Motor is working to finish its own deer detection technology. Its system will most likely use radar only, Toyota officials said, which would lower costs enough so that the technology could be part of more affordable models. It could be available within a year or so.
Toyota’s technology is based on more than three years of research on the back roads of Virginia and Montana, a stint at a deer sanctuary in Michigan, and months of crunching data from studies of car and deer encounters.
“Do they come to the road in groups or singles?” said Rini Sherony, an engineer at Toyota’s Collaborative Safety Research Center in Ann Arbor. “Do they run or walk? This is all critical information so we know what the sensor needs to look for.”
To answer those questions, Toyota conducted a study with Virginia Tech University that involved equipping 48 vehicles in the Blacksburg, Va., area with forward-looking cameras. One other vehicle had a camera and radar. The vehicles were driven more than 350,000 miles, and the cameras recorded 596 real-life encounters with deer on rural roads. In only one instance was a deer hit.
Toyota did similar work in Montana and mined a trove of data collected by federal and other road-safety studies that provided information on more than 200 additional encounters.
The carmaker found that encounters most often involved single deer, usually in dim light before 8 a.m. or after 5 p.m., usually on two-lane country roads where cars travel at 55 m.p.h. — fast enough to catch the animals by surprise. Usually drivers see deer when they are 30 to 100 feet away and have about 5.5 seconds to react.
“They try to steer but end up hitting something solid on the side of the road, a tree or a pole,” Ms. Sherony said. Hitting a deer can cause injuries, too, and can badly damage cars. Sometimes the animals are struck by the bumper and thrown into a car’s windshield.
Toyota next sent Ms. Sherony and other engineers to the Whitetail Hall of Fame and Museum, a deer sanctuary in Grass Lake, Mich., where they set up radar sensors and aimed them at the dozens of deer milling around. The idea was to record images of all different sizes and types of deer, from every conceivable angle, running, walking and standing.
The researchers also captured images from a type of sensor that uses laser beams, known as lidar. Unlike radar, lidar is able to see colors.
The exercise revealed some surprises. One was that younger deer have thin fur that reflects radar differently than the coarser coats of older animals. In the fall, males have full antlers, which also alters the radar imaging.
“It is important to know these differences,” Ms. Sherony said. “We didn’t know these things before we did the study.”
In the end, Toyota collected more than 53,000 radar readings of deer and is using them to program radar sensors to recognize deer in a fraction of a second.
The development work on deer-detecting software that will go in cars is now being finished in Japan. One challenge is tuning the system. Toyota has found that drivers don’t want a system that brakes the car too soon or too often.
“If the driver sees the deer himself, and is in control and is about to do something, but then the car brakes on its own, they say, ‘Hey, I was going to stop. Why did the car do that?’” said Chuck Gulash, director of Toyota’s Collaborative Safety Research Center. “Then people get annoyed and turn it off. So you have to get the right balance.”
For Randy Menard, a firefighter from Howell, Mich., deer-detection technology can’t come soon enough. In 2015, he hit three deer, and his wife hit two. One crash caused $5,000 in damage to his Ford F-250 pickup truck, another totaled his Dodge Intrepid.
“You rarely have time to react,” Mr. Menard said. “They just come out of nowhere sometimes. So something that gives you a warning or stops the car would be pretty nice to have, at least where I live.”