Probably a lot of path blur in photoshop.

https://planetphotoshop.com/using-the-path-blur-in-photoshop.html

So it’s probably photoshop as listed above but attaching a camera with a boom to the subject (in this case the subway) would get this effect in camera. A subway would obviously be hard to pull off irl but people do it with cars or other moving objects all the time. Look up “car rig photography”

It might be zooming in/out with a zoom lens during the exposure.

A similar edit is explained here: https://www.instagram.com/reel/CoaLei5I4ao/?igshid=N2ViNmM2MDRjNw==

Photoshop?

If not photoshop, then changing focal length and long exposure (longer shutter speed) at the same time.

Probably not even that long of an exposure as the train would be moving quickly. The other train is keeping pace.

Or they just masked and did this in post.

Looks like a photo with photoshop, a typical cliche of keeping the train untouched and adding a directional blur

I saw the video on Instagram and it’s a regular photo with lots of photoshop

Shooting on the train before it

My bet is this is a shot of a train slowing down at a station, and the camera operator is walking in pace with the train as it slows. Wouldn’t take a terribly long exposure to get this effect. It would just take a little luck to get it all just right.

Look up intentional camera movement or ICM