WHITE PLAINS, N.Y. (AP) _ A retired investment banker who was originally charged with attempted murder was given the minimum sentence for assault of 1 1/2 to 4 1/2 years in jail Wednesday for shooting a teen-ager during a traffic dispute on a parkway.

''You appear to be a good and decent person except for one terrible transgression,'' state Supreme Court Justice Nicholas Colabella told Arthur K. Salomon just before sentencing.

Salomon, 53, of Pound Ridge and Manhattan, is the grandson of one of the founders of the Salomon Brothers investment firm.

Under a plea bargaining agreement reached in March, Salomon pleaded guilty to the lesser charge of assault and Colabella had promised a jail term of two to six years in prison. The maximum is five to 15 years.

Colabella said he cut the planned sentence after receiving numerous letters and a pre-sentencing report. He said the jail term was ''justified under all the circumstances in this case.''

Salomon had been charged with attempted murder for shooting Gianluca Cotugno, 19, of Larchmont, once with a licensed .38-caliber revolver. Cotugno a student at Iona College, spent two weeks in the hospital recovering.

Salomon said June 19, 1987, the day he shot Cotugno, was a ''day I'd like to forget as much as the Cotugno family. ... The last 10 months have been hell. I don't expect the Cotugno family to ever forgive me.''

The two pulled over at a Scarsdale exit after an incident on the Hutchinson River Parkway in Westchester County. Salomon maintained when he pleaded guilty that Cotugno came toward him with his arms waving so he pulled his gun and shot him.

But prosecutor George Bolen said that as Cotugno approached Salomon's car, he saw Salomon pointing the gun at him, took down the license plate number and told Salomon he was going to notify police.

After Colabella told Salomon Wednesday of his right to appeal, Salomon said, shaking his head, ''There will be no appeal.''

Outside the courtroom, Salomon said he felt he had been treated fairly and ''I'm glad this whole incident is all over. I'll be away for a year and a half.''

Asked how he felt about prison, he said, ''I'll survive.''

Neither Cotugno nor his family were in court. The family lawyer, Stephen Heard, said the youth's $20 million civil suit against Salomon would proceed in state Supreme Court in Manhattan with a conference next month.