There should be a turnaround lane right before all border crossings.
Better build a 140ft wall -- 40ft below the ground and 140 above -- from one end of the US to the other along the Southern border.
There is one turn around lane right before the border, but you have to be in the inside (fast) lane to access it. All of the other lanes have concrete barriers preventing you from changing lanes and getting to the last chance turn around. The San Ysidro border crossing is a very confusing place unless you have been there many times.