Insecurity cams? About half don’t work

? About half the 4,313 security cameras installed along New York City’s subways aren’t seeing a thing — a blind spot in the crime and terrorism safety net for the nation’s largest city.

“A lot of those cameras don’t work, and maybe someday we’re going to get very badly hurt because of it,” Mayor Michael Bloomberg said Tuesday.

While cameras are out of commission in the subway, the cash-strapped Metropolitan Transportation Authority has also been forced to cut police patrol shifts on major bridges and tunnels on the weekends.

The problem of missing video came to light after two men were stabbed to death on the subway — and there was no camera installed in the station to catch an image of the killer. Darnell Morel and Ricardo Williams, both 24, were killed in a fight that started around 5 a.m. Sunday at the Christopher Street station in downtown Manhattan.

The New York Police Department says it doesn’t depend on the surveillance cameras set up by the MTA — instead, officers patrol the subways and set up random bag searches in stations around the city.