Four people emerged almost unscathed from a car crash off a 250-foot cliff.
It's very rare to survive such a crash, but not totally unheard of, an expert said.
Professor Jahan Rasty cited several Tesla safety features that likely helped.
The people who survived driving off a 250-foot cliff were lucky to live - and it helped a lot being in a Tesla, an expert told Insider.
Two adults and two children escaped with only minor injuries after plummeting off the rock face known as Devil's Slide, not far from San Francisco.
Dharmesh Patel, a 42-year-old Pasadena doctor, was arrested on charges of attempted murder after the crash. He was formally charged on Monday.
San Mateo County District Attorney Steve Wagstaffe told Insider on Tuesday that Neha Patel, his wife, told paramedics rescuing the family at the scene he had intentionally driven the car off the road.
Such a fall would likely be fatal in almost all cases, according to Jahan Rasty, a forensic engineer who studies crashes.
Rasty, who is a professor of mechanical engineering at Texas Tech University, talked Insider through the physics of the crash, and how Tesla's safety features likely helped.
Car crashes of any kind come down to the transfer of energy. If too much of a moving car's energy is suddenly directed into people's bodies, they will die.
When the car abruptly stops, that energy has to go somewhere, as Rasty explained. Car safety design is all about dissipating that energy away from the passengers.
One way is to strategically build the car so that it crumples on impact, using up the energy to bend the chassis. That process is called energy dissipation.
This photo shows a NASCAR crash where the crumple design is doing its job:
They were lucky to roll before the impact
No car is built with a huge, sheer drop in mind. If the car had fallen that whole height without stopping, it's very unlikely the passengers could have lived, Rasty said.
Rasty's job is to determine what happened to a car by examining the wreckage, and he described the likely events in this crash.
He estimated that the car went off the road at 77 miles per hour, fell about 200 feet, rolled on the cliff several times, then dropped another 50ft to fall square on its tires.
"The car is totaled, but the damage is pretty uniform all around it," he said of the wreckage imagery.
Every time the car hit the side of the cliff, a little bit of the energy was dissipated as a side panel crumbled, he said. This meant the energy was not all concentrated in a single place.
"That is really what saved them, the fact that the energy of the impact was distributed kind of evenly all, all around the car," he said.
If it had fallen nose first, the car would have had to absorb all of that energy at once.
All cars are not built equal
According to Rasty, they were very lucky to be in a Tesla.
Tesla roofs "are about 30% stronger in terms of crash resistance" than a regular car, Rasty said.
"So they can support about four times the weight of the car where the average requirement is three times the car's weight."
That means the car was not likely to collapse in on itself, which is a risk whenever a car rolls over.
The weight distribution helped too, he said.
A Tesla battery goes in the middle of the car, unlike a gas car which usually has its heavy engine right at the front.
This means the Tesla is less likely to fall nose-first and instead has a tendency to roll sideways.
Teslas also have a safety feature called a steel step frame, that is designed to redirect energy to parts of the car that can best handle it.
"Being in that Tesla definitely improved their odds," he said. "They're pretty safe cars."
Seatbelts and car seats were also essential
The car can only protect the passengers if they stay inside the car during the crash, Rasty noted.
Without seatbelts on and car seats for the children, they would have fared a lot worse.
Combined, Rasty said, those factors meant an ostensibly deadly crash instead became an unlikely survival story.
"Being in that Tesla definitely improved their odds," said Rasty.
This story was updated on February 1, 2023, to reflect the latest developments in the case
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