You will see tis brown roof thing over the top of Broker Bridge. Go to any entrance of the Broker Bridge then if you look closly at the bridge and you will see a narrow ramp on the bridge making a 'kind of' roof drive up that ( Probably best to have a fast car )( To do this glitch ) Have a Run up then drive up, but you will have to go very slow if you want to stay on top of the bridge...As soon as you've succeded up the narrow ramp press on the brakes to make car stop.... then drive carefully along the bridge.