Re: Silent (but deadly) trucks on the roads?
My local electric bus does a "ding" sound like a tram, which seems to work well in a "less than horn" situation. It seems to do it on proximity by the cameras, as it regularly dings at cyclists coming past.
A number of youths around my town have also fitted their petrol cars with a warning devices, that makes a "unst unst unst" noise that is apparently a combination warning and mating call. I hope our trucking brethren can pick something equally appealing :)