Cell Phone Signals blocked In The Holland, Lincoln, Midtown and Battery Tunnels.

Cell phones were used to trigger the Madrid train bombings, which killed 191 people last year, and are often used to detonate roadside bombs in Iraq. Authorities think last week's nearsimultaneous London blasts may have been sparked the same way.

That's why authorities blocked cell phone signals in the tunnels soon after the London subway bombings last week.

They did it, apparently, so terrorists couldn't use a cell signal to remotely detonate a bomb. But angry drivers said yesterday they felt less safe without a way to call for help in an emergency.

The MTA and Port Authority wouldn't say why they pulled the plug or when service would be restored. An NYPD spokesman said police never asked for a phone block.