The ad screen almost feels inhumane. There's no way to turn it off or even dim it. After a long flight, having that thing in your face can be really unpleasant. It's my biggest gripe with NYC cabs. It's just too 1984 for my taste.
What, of course there is. There's a red button in the lower-right hand corner you can hit to turn it off in most cabs; granted, there are some where you cannot turn the screen 'off' but you can turn off the display of advertising on it (and it just then says "Touch here to resume").
That "off button" doesn't turn it off, it makes it goes into a silent slideshow mode showing you more ads with an equally bright screen. Point is you can't win against the ad machine.
Take a brick with you.
I'd suggest some duct tape and a newspaper. Those are less conspicuous and you might get away with it without ending up in handcuffs.
I like you.
You definitely can turn off half the ad screens, and the other half you can at least turn down the volume