even now as i roared down that dual carriageway like a bullet along a gun barrel , part of me expected my vehicle to slip out of my control , to veer and lurch and strike one of the slanted concrete walls , ride halfway up and be yanked down again by gravity ; to cross lanes and smack the other wall picture a comical back and forth across the road and up and down the walls like a skater in a half-pipe , striking other cars , sending them spinning or overturning , yet not slowing , zipping ever downward in twists , until a river of vehicles rolled/grated/bounced to a neat stop at the flat bottom of the chute .