A hand gun will NOT! stop a motor vehical. Period. If the Officer did manage to shoot and disable the driver... Now we have a several ton missile going down the road at many miles an hour. Now what? Could the officer who fired the shot be held responsible for any damage the vehical may cause? Another issue is people trying to shoot out the tires. Tires are a relitively small angled moving target. Besides anyone know what tires are made of?
This argument on what round can shoot through a car is not new. One summer during the range cycle they dragged a bunch of old cars out to the range. A range instructor demonstrated how our service ammo (now considered weak) would penitrate auto glass, and auto body. 158 gr semi wad cutter ammo will pass through auto glass like a hot knife through butter. What did happen was the slope of the winshield, or rear window may cause the round to deflect.
Like Bamaranger said... Most agencies dont allow Officers to shoot at moving vehicals. The risk is far greater than any reward. My agency allowed shots at the vehical only if the vehical was used as a weapon against the officer and the officer was shooting to save his life, or if shots were being fired from the vehical.