JOHNSTON — A 17-year-old Warwick boy driving home from work Friday night was killed when his car collided with a sport-utility vehicle that the police said crossed into his lane on Hartford Avenue.

The accident occurred at about 7:40 p.m. along a stretch of Hartford Avenue that has a sharp curve, near Reservoir Avenue.

The Warwick teenager, whose name was withheld because of his age, was driving his 1993 Buick Century east on Hartford Avenue, said Deputy Police Chief Gary W. Maddocks Jr. A 1998 Ford Explorer, driven by Dawn Simas, 29, of 60 Read Ave., Coventry, was headed west on Hartford and crossed into the eastbound lanes, colliding with the teenager’s car, a preliminary investigation has shown, Maddocks said.

“It appears operator negligence and speed were a factor” in the accident, he said.

The police are investigating whether Simas was driving under the influence of drugs or alcohol. Officers at the scene found the butt of a marijuana cigarette in Simas’ car and several more roaches in her possession, Maddocks said.

The accident, which occurred at a busy time of night on Hartford Avenue, backed up traffic for several miles, and the state police assisted in diverting traffic.

“This was a very horrific accident,” Maddocks said. “It probably was one of the most serious accidents on Hartford Avenue in the past three or four years.”

Rescue crews quickly extricated the teenager from his car and took him to Rhode Island Hospital, where he was pronounced dead at 8:07 p.m. He had suffered massive head trauma, Maddocks said.

The airbag in the teen’s car deployed, but he was not wearing his seat belt, he said.

Simas was treated at Rhode Island Hospital for non-life threatening injures and released into police custody Friday night. She has been charged with possession of a controlled substance, operating a motor vehicle in possession of a controlled substance and refusing to submit to a chemical blood test, Maddocks said.

He said the accident is still under investigation and more charges are pending.

The police are seeking a subpoena to obtain the results of a toxicology test administered by hospital personnel while treating Simas. The police are also looking into Simas’ whereabouts prior to the accident.

Simas was arraigned yesterday afternoon at police headquarters and released on $5,000 bail. She is scheduled to appear in District Court, Warwick, on Wednesday.