An Ontario Provincial Police officer who was dragged by a car during a 2017 traffic stop has launched a civil suit after criminal charges were dropped against the alleged driver.

Constable Patrick Chatelain, 38, was left with a traumatic brain injury and post-concussive syndrome after he was dragged more than 100 metres by a rental car whose driver he pulled over for littering on Sept. 4, 2017.

Chatelain says he's hoping the civil court will find someone responsible where the criminal court did not.

"I know what happened," Chatelain said in an interview with CBC News. "Yet in terms of the eyes of the court, nobody was held accountable."

Dash cam footage captured hit and run

The 2017 traffic stop started like any one of the hundreds of others Chatelain had conducted as an officer with the OPP detachment in Mississauga, about 28 km west of Toronto. He had pulled over a vehicle on Hurontario Street near the exit ramp to Highway 403 in Mississauga.

He was standing next to the driver's side door when the car suddenly accelerated, according to a statement of claim filed in the Ontario Superior Court of Justice in Milton, Ont., Monday.

Chatelain grabbed on to the headrest of the driver's seat and was pulled along with the car.

Dash cam footage from a passing vehicle shows Chatelain eventually pushing himself off the car and rolling on the pavement as other vehicles swerve and brake around him.

WATCH | Hit and run captured on dash cam of passing vehicle:

Footage from a dash cam in a passing vehicle shows Ontario Provincial Police officer Constable Patrick Chatelain being dragged by the car he had pulled over during a traffic stop on Sept. 4, 2017. 0:15

"I distinctly remember hearing the engine red lining, and it was just so fast, and I could feel the wind on my face," Chatelain said. "I parachuted before, and it was similar to, you know, when you step out of the airplane for the first time - that wind in your face.

"I just remember rolling, rolling, and all of a sudden, I heard a very hollow bang, almost like when you drop a coconut on the ground. And that was my skull impacting the asphalt."

Chatelain blacked out after that. He was rushed to Sunnybrook Hospital in Toronto with a head injury. He has been restricted to desk duty since the event.

"I tried to go back to work right away. And over time, the symptoms just became too much. I wasn't able to cope with those injuries."

LISTEN | A bystander calls 911 to report the hit and run:

A bystander calls 911 after witnessing an Ontario Provincial Police officer being dragged by a car he had pulled over. 4:59

Rental car company, insurance firm named in suit

The lawsuit filed Monday names Enterprise Rent-A-Car Canada, the Aviva Insurance Company of Canada, which insures OPP cars, and Ian Anthony Green, the man who rented the vehicle and whose name appears on the Motor Vehicle Collision Report filed after the incident.

It also names a "John Doe" in part because of questions raised around who was behind the wheel of the rental car at the time of the traffic stop.

At the time of the hit and run, police told CBC there were four people in the car when it was pulled over. They arrested Green several hours after the incident and charged him with obstructing a peace officer, dangerous operation of a motor vehicle causing injury, criminal negligence and failing to remain at the scene.

But days before a scheduled preliminary hearing in January 2019, the Crown dropped the charges because there was "no reasonable prospect of conviction," according to a spokesperson at the Ontario Ministry of the Attorney General.

OPP Constable Patrick Chatelain discusses what he went through the day he was dragged by a car during a routine traffic stop near Toronto in 2017. 0:49

Green's defence lawyer at the time, Luigi Perzia, told the Toronto Star at the time that "there was a serious identity issue, and it was not Mr. Green driving that car."

Chatelain and his lawyer, Michael Smitiuch, said the problem with the criminal case boiled down to an inability to definitively identify who was behind the wheel.

"If it wasn't Mr. Green, he certainly should know who was driving," Smitiuch said. "He was the one who rented the car, it was not reported stolen. And so, if it wasn't him, he knows who it was. And so we hope the truth comes out."

Looking for answers through civil process

CBC News made numerous attempts to contact Green, including reaching out to his former lawyer and visiting his last known home address. Those attempts were unsuccessful.

Aviva Insurance said it cannot comment on the case because it is before the courts. Enterprise did not respond to a request for comment.

Smitiuch says Chatelain is seeking the accountability that he wasn't able to get through the criminal system.

"Sometimes, through the criminal process, you don't always get the answers that you want," he said.

"And through the civil process, there are documents that are produced, and there is other information that is brought up. So through that process, more information becomes clear."

Chatelain, who works out of Mississauga, west of Toronto, has been restricted to desk duty since the 2017 hit and run. (Ontario Provincial Police)

Chatelain said the experience has made him more cautious, a sobering admission for a man who once made the news when he rushed to the scene of a crash.

In 2008, Chatelain, who had served as an army medic in Afghanistan and was working as a paramedic at the time, came upon an accident on Highway 401 in Mississauga while off duty. He managed to put out a fire in the wreck with a fire extinguisher he had in his vehicle and attended to the four people who were seriously injured.

Traffic stops routine but unpredictable

Chatelain's lawyer said he hopes the case will bring attention to the hazards of policing.

"I think it just highlights the dangers our officers face, and hopefully, there's more support through the laws and the public," Smitiuch said.

Despite the fact that traffic stops are routine, they are also among some of the most dangerous interactions police have with the public.

In March alone there were several reported incidents in southwestern Ontario: a female officer was allegedly repeatedly punched by a driver following a traffic stop in Toronto; another officer was dragged by a fleeing car in the Regional Municipality of Durham, 60 km northeast of Toronto; and in London, Ont., an officer dragged while conducting a traffic stop on the driver of an SUV reportedly stolen from a dealership.

In February, a motorcycle drove into an RCMP officer in North Vancouver, B.C., after officers conducting a traffic stop flagged it down.

According to the Canadian Police Association, 22 officers have been killed during roadside traffic stops since 1975.

There is no centralized database that tracks on-duty injuries for police, but what makes traffic stops dangerous isn't just that they happen along busy roads and highways, said Brian Sauvé, co-director of the National Police Federation.

"It's one of the higher-risk activities police officers do routinely because of the unknowns," Sauvé said. "What is the intent of the driver?"

Sauvé, who was once run over during a traffic stop, says even though officers may run the licence plate of a vehicle through a background check, they have no idea who is actually behind the wheel or whether the vehicle has been stolen but not yet flagged as such.

Nevertheless, Sauvé says most of the five to 10 traffic stops officers conduct in an average shift are without incident.

Chatelain, too, wants to believe that his traumatic experience is the exception, not the norm.

"I like to think that this was an isolated incident," said Chatelain. "I don't want this incident to mark my career. And I don't want going forward to always be suspicious of individuals. I don't want to always work in fear of this happening again."