Originally Posted by MasterOgami
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.
I rewatched it several times before making my comment. The cars don't appear to be slowing down to me. If they are, it's extremely closely cut so that it's hard to tell that they were effected beyond the lights, so again, poor communication on the director's part if that was the goal.
I don't recall hearing
them restarting, but I'll take a closer listen. Hadn't considered the audio angle, so good call.
Did notice that there are some stopped cars later on, but we could just as easily chalk that up to them trying to stay out of the way of the chase, as drivers tend to do in real life when an emergency vehicle speeds by.
Supporting that idea is the fact that Batman has stopped using the EMP pulse at the point we see them stopped/stopping and hasn't even approached them yet, AND we see many of the cars' brake lights on. So it would seem they stop themselves.
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.
The rifle is glowing in the dark during the scene, so it looks like there's a mode where he just creates a field and doesn't need to fire it.
To me it looks more like the guy stops on his own to try and shoot Batman, but gets tackled.
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.
It isn't clear that that's necessarily what stopped the bike, again. It just looks like the cops got hold of him. I mean, we can stretch and guess that's what caused it, but it cuts away and then cuts back afterward to the cops having caught up to him.
The sore thumb is that he drove off for a considerable and indeterminable (as it cuts away) distance seeming utterly unscathed after being directly blasted, while the other bike stopped immediately - assuming it wasn't intentionally, to take aim and fire at Batman. So there's an inconsistency and an uncertainty pervading the effectiveness of the gun to stop engines throughout the whole scene.
I feel like it's possible
Nolan was going for what you're saying, but he established it very weakly. So weakly that many people were left kind of confused.
Could've used a few seconds of talking to Fox to straighten it out. Or at least they could have better demonstrated cars actually being stopped by it.