Horn won't work
Problem is, they're so damn busy textin' 'n doin' "other" stuff down in their lap, they don't SEE anything that subtle!!
When I was stationed at Miramar in the 70s I got so tired of slow hippie Vee dubs on the freeway I bought a set of those air/ electric horns for the RR. Sometimes it helped.
The first owner of the car used to have a 65 Chevelle with a 350 in. He had a 400 watt inverter --quite unique, back then-- installed in the car, and had the primary power rigged through a solenoid switched to the horn button. The "default" was with the horn button switched to the inverter, and plugged into the inverter -- under the hood -- was a great big 120V AC submarine KLAXTON. AAAAAAOOOOOHHHHGGGAAAAA!!!!