That same highway you speak of, things could go wrong and there are cars out there when we raced. Maybe not on our side of the road, but on the other side there was.
You and I have been on that road NUMEROUS times and you have to admit, there are cars coming the opposite direction. You would be foolish not to admit your tire couldn't blow out and you cross the median into oncoming traffice. There is always "light" traffic on that highway even at 2 a.m.
I've also seen deer along that same highway. Hitting one of them could cause your car to go in a different direction and go into oncoming traffic.
I'm just being realistic on the highway comment. I will agree though that I think THAT particular section of highway is the SAFEST at 2 a.m. IF you are going to street race, BUT it's not 100% safe. I would even go as far as saying I think that is the ONLY somewhat safe place to race that I know of because of the fact it has very light traffice late at night.
It took me a while to stop lieing to myself about it being safe.
How many times have you driven the road you are going to race on to check it for debri? I never did. I sent someone ahead of us to check for police and deer, but if they don't look for debri your playing russian roulette. Hitting something at 140 mph on the highway could be fatal especially popping a tire.
I have to agree with Jaime, at the track you have the best surface available and paramedics and a fire truck standing by.

If debri gets on the track they stop racing until it is removed by the sweeper truck, even the littliest pieces.