An Overwatch trick allows Zarya to fly over the buildings on Oasis by properly using her shield against a speeding car. Players have known since the map first released, the danger of the speeding cars on the highway
It's certain death going on the road, and it's been tested countless times. You can't jump it, hop over them, spin past them, or dodge them. You will get hit and die.
The trick is much more difficult than simply popping your shield and standing in front of a car. From the looks of it, you have to time the shield, look at the ground, and use your secondary fire seconds before the car hits you. The shield will keep you alive when you make contact with the car, and the secondary shot on the ground, will give Zarya a boost when she jumps. The car will hit you, and if you time it right, launch you high enough in the air to fly over the building surrounding the center point.
Be prepared to die many times before ever landing this correct, and even then, it's not like flying over the building will do much. It may give you an element of surprise once, but that's about it.