Pedestrians, runners and cyclists share the loop road in Prospect Park. Cars are allowed in one lane during rush hour on week days. A new petition is calling on Mayor Bill de Blasio to ban cars from the park. View Full Caption Flickr/Prospect Park

PARK SLOPE — The long quest to get cars out of Prospect Park and Central Park could soon move into the fast lane — Mayor Bill de Blasio is expected to announce a ban on cars in parts of both parks this week, Capital New York reported Wednesday.

De Blasio is expected to permanently ban cars from Prospect Park's West Drive, but vehicles would still be allowed on the park's East Drive, sources told Capital. In Central Park, the mayor is expected to bar traffic from a northern portion of the park, Capital reported.

The mayor has long been a supporter of a car-free Prospect Park, dating back to his days as a City Council member representing Park Slope.

The shift in car policy would be a victory for advocacy groups like Transportation Alternatives, which has long supported a car ban in city parks, and park users like Michael Ring, a runner who recently launched a petition calling on de Blasio to permanently bar vehicles from Prospect Park.

Ring said no one from the Mayor's Office had contacted him about his petition. The Mayor's Office did not respond immediately to a request for comment.

If the announcement happens, Ring said it would be a "partial celebration" because the park's East Drive would still be open to cars during rush hour on week days.

“I’m not going to stop until he closes the other half," Ring told DNAinfo New York. "The morning should be closed too. But it’s a very good start."