By now, you’ve probably heard that new hybrid and electric vehicles will have to be factory-equipped with a noise-making system to ensure they can’t sneak up on pedestrians.

It’s not a bad idea, really, but this is definitely once situation where the devil will be in the details. And boy-howdy are there a lot of details.

Would you be surprised to hear that the actual rule runs to 370 pages? No, I wasn’t surprised either; this is a federal rule, after all. What did surprise me was that the summary is less than five pages long. Now that’s efficiency! But I digress.

One of the details I’m dubious about is the estimate of the number of accidents the rule will prevent. Next time you drive somewhere, watch the pedestrians. In particular, take a close look at the ones who step out into traffic without looking both ways. My bet is that most of them are wearing headphones.

I’m not suggesting the new rule is pointless. If nothing else, it will be helpful to the blind. But 2,400 injuries per year seems optimistic to me.

That aside, what I find most interesting about the rule is that it doesn’t specify what kind of sound the cars should produce. The rule sets out standards for minimum volume at various frequency levels and how the volume should change when the vehicle speeds up or slows down, but there’s nothing in those three hundred seventy pages that describes the actual sound.

Each manufacturer is free to choose whatever sound they wish, a long as all vehicles of the same make, model, and year use the same sound. Bets on whether some manufacturers will choose to use their advertising jingle as the sound? I suppose it’s too much to hope someone will use a voice saying “Hey, look out! Car coming! Damn it, don’t play in traffic!”

More seriously, given the need to vary the sound according to the speed of the vehicle–and the need to upload new firmware to fix bugs–manufacturers are going to hook the sound system into the same inter-car network system as everything else.

Lest anyone forget, many of the radio-based car hacks we’ve seen use the entertainment system as a point of entry. It’s clear that, to date, manufacturers haven’t given enough thought to separating components.

That being the case, how long will it be before hacks start appearing that let you take over the safety sound system and replace the factory-installed sound with anything you want? How long will it take before the RIAA starts suing motorists for “sharing music” by routing the output of the stereo into the external speaker?