For Cavon Hajimiri, hindsight may actually be 20/20.
He’s talking about his invention called Hindsight, the first wearable pedestrian-safety radar that works as an early warning sensor that can detect a vehicle from behind up to 300 feet away by audible beeps. If using the app, a vibration also is sent to the wearer’s smartphone in their pocket.
When the runner or pedestrian doesn’t see the approaching car, the device provides an alert, giving up to 7 seconds of early warning time that can save a life.
“You wear it around the waist,” said Hajimiri, a 17-year-old rising senior at Polytechnic School in Pasadena, located across the street from Caltech. “It will detect anything come up from behind you. It’s sort of like eyes in the back of your head.”
Hajimiri developed the lightweight device on his own. He designed the radar using a specific algorithm to match a pedestrian’s or runner’s movements, going through 18 different radar designs. This one uses a high-frequency circuit board the size of a matchbook.
It uses a specific kind of Doppler radar to measure the distance of the vehicle and send back the signal to the wearer. It costs about $10 to manufacture and keeps a charge for about 20 hours, he said. But he’s still in the pilot phase. He doesn’t yet have a price range or a date certain as to when it will become commercially available.
The talented senior from La Cañada Flintridge, who won three awards at a science and engineering fair in Phoenix recently, plus was inducted into the National Gallery for America’s Young Inventors this year, clearly likes tinkering with sophisticated engineering concepts — and is good at it.
He wants to study engineering but doesn’t yet know what college he will attend. He started working on the Hindsight in 2022, designed the radar portion in 2023 and also figured out how to get it patented, with some help from a family friend who is a lawyer.
At an interview under the eaves of the school entrance on Monday, July 6, he showed his box of circuit boards that he went through to find the best one. He carries Hindsight in his backpack wherever he goes.
“For me, it is like my way of adding something,” he said. “Inventing is not just like some random combining of parts. I think putting them together in a certain way. That is my stamp on the world. It is also a part of me.”
Besides enjoying the process of making new things and seeing how they work, designing Hindsight, Hajimiri, was also personal.
He remembers the feeling of walking on Robin Hill Road in La Cañada Flintridge, near where he lives, when he was 13. There are no sidewalks. And one day, when he and a friend were walking on the side of the road, he was nearly run over.
“The car came up very close on my left side,” Hajimiri said. “It was pretty shocking but I could feel the wind of the car going by.”
And there were other close calls, too.
The search for an early warning device for pedestrians and runners came up empty. So he went to work.
He’s particularly concerned about the number of fatalities of seniors who walk on busy streets or hearing-impaired individuals.
In fact, during a 10-year period, from 2015 to 2024, fatalities in unincorporated Los Angeles County among seniors 60 years or older made up about 39% of the total pedestrian deaths, according to the UC Berkeley Safe Trec’s Transportation Injury Mapping System — or TIMS — a leading source in the state on the topic.
In the city of Los Angeles, there were 336 road fatalities in 2023. Of those, 179 were pedestrian deaths. When you add in 24 bicyclists killed that year, pedestrians and bike riders made up more than 50% of all the road fatalities in L.A., according to Los Angeles Police Department and city statistics.
Damian Kevitt, founder and executive director of the group Streets Are For Everyone, cited these statistics when asked about Hajimiri’s Hindsight soon becoming available to pedestrians.
“I have not heard of any devices like this,” Kevitt said. “I think it is very cool sounding. Anything you can do for pedestrians who are the most vulnerable road users is a good thing.”
In 2025, traffic fatalities of all kinds exceeded homicides in Los Angeles — for the third consecutive year.
Wesley Reutimann, programs manager of Active SGV and former president and founder, supports safe bicycling and walking. Both he and Kevitt said streets are getting less safe for pedestrians and bike riders.
“Unfortunately,” Reutimann said, “the trends are not going in the right direction.”
There are taillight bike devices with cameras that transmit images to a smartphone or bike computer on the handlebars. These can cost $150 to $250 each. But Hindsight is specially designed for walkers and joggers, using a tailored algorithm and specially designed radar system.
“There’s a clear traffic safety crisis,” Reutimann said. “I don’t think there will be one solution. But it will be interesting to learn how (Hindsight) might help.”
Reutimann advises joggers to run against traffic. Some do, but Hajimiri said most walkers don’t enjoy walking and seeing the cars coming toward them, so they walk with the traffic. Another important safety tip is to wear bright clothing, even fluorescent vests, Reutimann said.
One of the danger zones not surprising to anyone crossing a city street on foot is when cars make a left turn heading into the pedestrian who has the “walk sign.”
“It’s when the driver isn’t paying attention that you are in the crosswalk,” Reutimann said. “Also, drivers turning left tend to move at a higher rate of speed than when turning right.”
Hindsight, Hajimiri said, can detect the left-turning car but the wearer will have less time to react, since the distance is shorter.
“If the vehicle is coming from behind you, you will get an early warning,” he said. “If it comes at an angle, or stops and accelerates, it is a shorter amount of time.”.
On Monday, he was testing the device strapped to his waist on Arden Road in Pasadena. Each time a car or truck approached from behind, the device signaled. It can also detect a bicyclist, who can also cause a collision, he said.
In real-world testing, the device detected 340 out of 340 approaching vehicles, he reported and submitted to the Regeneron International Science and Engineering Fair in Phoenix. Hajimiri was the highest-placing U.S. finalist in his category. He also won Project of the Year in 2025 at the California Science and Engineering Fair.
He is distributing a survey (hindsightsurvey.lovable.app) to anyone who walks or jogs on urban or suburban streets, especially where sidewalks are missing. He wants to know their thoughts on the device and possibly what can be improved. This is part of the next step — a pilot program. That could mean getting the device to target groups for testing.
Another question he is looking into is whether a variation of the device could be used to detect heat, fire and wind — all recipes for wildfire disasters. He knew several students who lost their homes in the January 2025 Eaton fire.
He and a team of classmates are working on something called the “EmberAlert,” a wildfire detection and monitoring system to help first responders and homeowners get a quicker, more accurate read on where a fire is heading and when.
“There’s not a lot out there for keeping track of fires and early detection,” Hajimiri said. “I think EmberAlert can help firefighters and homeowners see where the fire is going.”
He will work with the Pasadena Fire Department during a future controlled burn to place sensors and study the data produced.
“That may be a way to detect and also to deploy the firefighters to the right places,” he said.
While rear-facing radar systems are on the market for bicyclists, they are not cheap, Hajimiri said, adding his heart is with protecting walkers and joggers.
“Pedestrians have significantly more fatalities than bicyclists,” he said, as someone who does a lot of walking. “Getting the pedestrian agency is a really important thing. And when you hear a car is coming, you can avoid that fatality.”