Highway 10 is the longest dead straight road on earth, covering 140 miles (240Km) in one stretch according to Guinness.
It links Haradh (Highway 75) to Al Batha and is a total desert land.
Bonus Record:
Highway 85 – Saudi Arabia . Not a straight road. From Jubail on the coast to Turaif on the border of Jordan. The Highway is 693 miles long and takes about 9 hours to drive in one go.
______________
Saudi Arabia