They were going down an embankment. The road is at the top of the embankment. You can't see over the edge from the shoulder.
The helicopter pilot said you most likely wouldn't be able to see it from the road, as he could barely make it out from the air.
Are you sure that you can't see the tire tracks leaving the road down the embankment?
Based on one of the news reports last night (video) you can clearly see the tracks leading away from the road.
Also the pilot made the comment in an interview on CNN that he arrived at the area the same time LE was stopping "probably seeing the skid marks leading off the side of the road."
So I asked if anyone has a photo of the skidmarks...seems like a logical and reasonable request...unless of course you don't want people to understand how it is possible for them not to see the tracks last week...a simple photo could clear up that issue.