Big Rig Parking Lot On Google Earth
We walked the phenomenal Bridge while parked at the Parking Lot shown in VegasDan pictures linked above. There's a separate Big Rig Parking Lot just East of that Parking Lot; clearly visible on Google Earth in their 06/11/2011 image. You can even scale the size of the Lot spaces relative to Vehicles going by in that Satellite pic.
The wide, double yellow line at the Parking Lot entrance tells me you've got to be heading West [with the Dam behind you] to make a legal right turn into this Big Rig Lot.
There's a long, gradual, serpentine path from the small Vehicle Lot up to the West end of the Bridge. A must-see example of Civil Engineering...