The phrase "highway stretches" refers to long sections or portions of a highway or road. It means the specific parts of the road that extend for a considerable distance without any interruptions or intersections. Full definition
Our time in the X1 was spent navigating busy city streets as well as open highway stretches and there was never a point when we felt the car could do with more power. (indianautosblog.com)
I averaged less than 8 L / 100 km over a week of mixed city / highway driving and it dipped into the six range on a couple of flat highway stretches. (autofile.ca)
The new hard top looks amazing and noticeably quiets the cabin, making long highway stretches less stressful. (cnet.com)