A highway IS a public road, so there is no problem calling it a 公 (public) 路 (road).
Let's step back a little and consider this: If you break down the English word "highway" into "high" and "way", a learner coming from a different language background may well be wondering why. Since a highway is not necessarily high in elevation,...
actually this group of words is called 同义复合词
1.make the definition more clear. if you only use one character, it may have many different meanings.
2.enlarge the meaning. eg: 牙齿，牙 and 齿 both mean a certain part of the tooth, but when combined, it means the whole group of teeth.
3.increase rhythm. in some ancient poems, there ...
老外 is an abbreviated colloquialism of the formal term 外国人 (foreigner).
外 (foreign) 国(country) 人 (human) = foreigner
洋人 literally means “overseas human”, which is an archaic term for “foreigner”.
① [original meaning] sea, ocean;
② [extended meaning] overseas.
"感", more objective, the feeling that surroundings impose on you. "冷感", "热感"
"觉", more subjective, the feeling from your heart (/mind/senses) about surroundings. "味觉", "视觉"
Yes, they are quite similar, and in some cases, they both mean "feel/feeling".
But in some other cases, you can find ...