Electric cars can be whisper-quiet -- but that will change. If you buy an electric vehicle after September 1, 2019, it'll automatically make noise anytime it's traveling at speeds slower than 18.6 miles per hour.
The rule has been a long time coming: Congress passed the Pedestrian Safety Enhancement Act way back in 2010. That gave the NHTSA until January 2014 to finalize a mandate for EV noisemakers, but the government body kept pushing that deadline back.
And now that it's finalized, automakers will have nearly three whole years to put waterproof noisemakers on their cars -- instead of the 18 months originally envisioned.
Still, better late than never, and many automakers may move quicker than the law requires. Nissan's Leaf and Kia's Soul EV have had noisemakers for years now.
The NHTSA estimates that the new rule will prevent 2,400 injuries per year. You can read the full rule (PDF) right here.