The father of a bus driver who pleaded guilty to sexually assaulting a teenage girl and having sex with her has been sentenced to 20 years in prison.

A Montgomery County judge sentenced William Smith, 57, to 20 to 30 years in federal prison Monday for his role in the alleged sex assault and sexual abuse of a 16-year-old girl.

Smith pleaded guilty in January to one count of sexual exploitation of a child.

Smith, who has been in custody since his arrest, was arrested after the victim reported the alleged incident to Montgomery County police in September 2015.

Smith told police he was at a bus stop when he and the teen, who was 17 at the time, were asked to move in together.

Smith told investigators he had sex with the girl while she was at the bus stop.

The teen testified that she was intoxicated and Smith touched her inappropriately, but police did not find drugs or alcohol in her system at the stop.

Smith had worked for the Montgomery County Department of Transportation for about five years, including two years as the driver of a school bus.

He was fired from his job as a school employee on May 31, 2016.

Smith is due back in court on Jan. 22 for sentencing.