The three of them were really narrow, so as automobiles got bigger, driving through them, especially during traffic, made them "awful", as evidenced by this picture of the one on 84th Street: https://bridgehunter.com/photos/27/35/273580-L.jpg
The nickname was also used in advertising for Mangelsen's.
UP - 120th Street "Awful Tunnel"
Posted August 23, 2018, by Clark Vance (cvance [at] dogmail [dot] com)
The three of them were really narrow, so as automobiles got bigger, driving through them, especially during traffic, made them "awful", as evidenced by this picture of the one on 84th Street: https://bridgehunter.com/photos/27/35/273580-L.jpg
The nickname was also used in advertising for Mangelsen's.