The completely serious film (Man on a Swing) opens with a one minute-20 second scene shot with a camera mounted on the police car roof about a foot behind the flashing light bar. While I am sure it seemed dramatic in 1974, it's impossible to view now without remembering the comedic rendition of the same viewpoint that forms the opening of "The Naked Gun".
While I can't be sure this was the only "cop movie" that had a similar opening sequence, it's pretty clear to me that this film alone would have been sufficient to inspire the Naked Gun spoof scene.
Review of Man on a Swing
