Katie Shields, 18, a sixth form pupil at The Deepings School, died after her car has hit by a 4x4 driven by Charles Dobney as she waited to make a right turn on the A16 at Hop Pole near Spalding.
A jury heard that Dobney's Grand Jeep Cherokee had been travelling at more than 70mph on the 50mph limit "arrow straight" road.
The jury at Lincoln Crown Court took less than two hours to convict him of causing Katie's death by dangerous driving on April 26 last year.
Recorder Sam Mainds adjourned sentence and granted Dobney bail on condition he surrenders his passport.
"You must understand a prison sentence almost inevitably follows in a case like this," the judge told Dobney.
The judge also asked to be given details of an earlier fatal accident in which Dobney was involved.
Dobney, 51, was at the wheel of a Mercedes estate which plunged into the River Glen at Pinchbeck late on a Friday night in August, 1993. Dobney escaped from the sinking car , but his wife Yvonne, 32, died in the accident.
This week the jury heard how Katie Shields was returning to Hop Pole after a shopping trip when she was hit by Dobney in broad daylight.
Mark Van der Zwart, prosecuting, said Dobney's Jeep hit Katie's car as she attempted to turn off the A16 onto a track leading to her family home. Katie died instantly from her injuries.
Mr Van der Zwart said in the minutes before the crash Dobney's driving attracted the attention of other motorists because of the speed he was travelling at. Tests showed that he was driving at a speed of at least 70mph when the collision happened.
Motorist Mavis Taylor was overtaken by Dobney, of Park Lane, Surfleet, moments earlier.
"The 4X4 overtook her at high speed, so much so that it made her jump," said Mr Van der Zwart.
Dobney, who did not give evidence at his trial, later told police he had hardly any memory of what happened in the moments before the collision.
Afterwards Katie's parents Kevin and Christine said: "All we would like to say at the moment is that we are happy with the verdict."