A video posted on YouTube Thursday morning shows three dimwits hanging on the outside of a moving 4 train.

The video shot by someone standing on the platform of the 149th Street station shows three teens at the back of the subway holding on as it takes off.

“Believe that you can make it!” shouts one of the onlookers right before the train pulls out.

People on the platform scream in horror and amazement as the kids wave and salute back to them, the video shows.

Young people surfing on trains has become a chronic problem around the city in recent months. In November, a boy was injured when a train operator saw him hanging off of a 1 train at the Christopher Street station. And in December, a man was decapitated when he tried surfing on a F train at the West 4th Street station