State Route 142, (SR 142) also known as Carbon Canyon Road for most of its length, runs southwest from State Route 71 in Chino Hills, through Olinda Village to its intersection with Lambert Road and Valencia Avenue in Brea. At the intersection, the highway turns south onto Valencia Avenue and ends at State Route 90, Imperial Highway. The eastern portion of the route is known as Chino Hills Parkway.

It is signed as a scenic route from the Orange-San Bernardino County line to Peyton Drive in Chino Hills. It is a popular shortcut between the Inland Empire and the business centers of Brea and surrounding Orange County; however, the road has multiple tight curves, so travel is not recommended for long vehicles, such as big rigs.

SR 142 is part of the California Freeway and Expressway System and is eligible for the State Scenic Highway System. However, it has not been designated by Caltrans as a scenic highway.

SR 142 begins in the city of Brea as Valencia Avenue at a junction with SR 90. The road heads northwest to an intersection with Carbon Canyon Road, which assumes the designation of SR 142 and continues east through Carbon Canyon Regional Park. SR 142 continues into the community of Olinda before crossing into the Sleepy Hollow area of the city of Chino Hills in San Bernardino County.

SR 142 continues northwest through Chino Hills to an intersection, where it continues eastbound on Chino Hills Parkway. The highway ends at an interchange with SR 71 on the border of Chino Hills and Chino, near the California Institution for Men, a state prison.

Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, and do not necessarily reflect current mileage. The numbers reset at county lines; the start and end postmiles in each county are given in the county column.