A few ideas:
You hear the crack of gunfire in the distance.
A car screeches wildly around the corner and blazes down the road.
A woman screams in the distance.
A group of gangers shove a weak looking shirt to the ground and demand payment for safe passage.
A street fixer calls out in , shaking a tray of ancient looking progias.
A steady stream of traffic rolls down the roads.
A dirt-covered courier is stopped by a Judge who begins questioning them about their destination and identity.
A WJF AV cruises overhead at a slow, steady pace, kicking up dust and a few chy notes into the air.
Well, I don't spend enough time in Green to have some good ideas, but you get the picture.