Slasher flees onto tracks

A man slashed another straphanger in the head aboard a Manhattan subway train late Wednesday — and then escaped onto the tracks, authorities said.

The suspect, described as in his 40s, got into a squabble with the 21-year-old victim on a southbound A train near Penn Station at 9:30 p.m.

At some point during the fracas, someone pulled the emergency brake, bringing the train to a halt, police said.

That gave the suspect the chance to bolt. He was still on the loose as of Thursday.