Stop signs must be destroyed by wearing the Catalyst outfit. They are mainly located in cities but their number differs from one city to another.
Pleasant Park is a very good place to end this challenge: the city has numerous stop signs. Salty Spring is also interesting because 3 panels are located next to each other in the heart of the city. On the contrary, Mega Mall and Paradise Palm have relatively few stop signs. Don't waste your time with Neo Tilted, which has almost none.
