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Self-driving Waymo cars keep SF residents awake all night by honking at each other
(arstechnica.com)
This is a most excellent place for technology news and articles.
Trains have even more obnoxious horns though.
And are legally required to blast them in populated areas
They usually only use the horn at crossings. Automated trains are grade separated. The SkyTrain rolls through Vancouver all night and you can hardly hear it.