Originally Posted by RustyCage
Dig the article, and it's obvious what EMPs do, but the movie doesn't sell the concept.
Computers being the heart of cars (much less motorcycles) rather than just functioning as less major assistance is a relatively new thing by my understanding and hasn't completely phased in, so it seems like a niche tactic. It would only be effective on newer cars, so that's a pretty big gamble - especially if you have to stop mid-chase to fire it.
After studying the scene, every car he passes appears to still be driving just fine despite the lights going out briefly, so that makes one think the gun has a pretty soft effect on vehicles, or that the engines of the vehicles aren't susceptible to it (including, obviously, the motorcycle which he fires directly at). The primary focus seemed to be cutting the lights (which were definitely electronic).
Either way, if shutting down the engines was the goal, it clearly didn't work. Maybe we're meant to assume that Batman guessed his average looking motorcycle might be more cutting edge than it really was.
Which is fine, but the fact that it's so vaguely presented creates a pause in many viewers. One of many 'huh?' moments where the suspension of disbelief is broken by logic gaps or lack of explanation.
Ultimately, the fact that it had zero effect on any engine in the entire scene makes me want to say he was more likely going after the tablet making the transfer.
The EMP rifle is designed to disable electrical systems, so it actually would work on a car/bike/whathaveyou as long as it wasn't a pre-1970s model, in which case the rifle wouldn't have any electronics to knock out (as I understand it anyway). If the EMP disables the engine control unit, I imagine the engine's going to stop.
Take another look at the scene, its not simply that the headlights are turning off, but the engines are cutting out as well and the cars are slowing down. You can hear them restarting as the bat-pod moves ahead and the area is no longer under the effect of the EMP.
One motorcycle is caught in the EMP emanating from pod/rifle/whatever device Batman's using and the hostage manages to hop off and escape. Batman takes that driver down and then lifts the rifle to manually fire a pulse more or less -directly- at another bike that's out of range of the "general blackout" method he had been using. That bike is disabled as well
, as the next time we see it its on the ground and the driver is attempting to flee on foot.
In short, Batman was using an EMP to disable lights/vehicles and was successful on both counts.