The drawing depicts three workers raising together a clenched fist, a symbol of resistance. There is also a regulated parking sign.
DalTux
CC BY-SA 2.0
<a rel="nofollow" class="external free" href="https://www.flickr.com/photos/daltux/27733481879/">https://www.flickr.com/photos/daltux/27733481879/</a>