Would using "peaks and valleys" be more correct or is there an appropriate word/term?
The “ups and downs” in an undulating road can be referred to in many ways but the following are some of the most common.
For the “ups”, particularly in informal conversation, “hill” or “bump” (for smaller features) might be most often used, but another possibility is “crest”. “Crest” is used in a specialised technical context too when discussing the “profile” or “vertical alignment” of roads and highways.
For the “downs”, the most common term is “dip” (although “valley” and “depression” are also possible). “Dip” is used technically too but “sag” is a particularly technical term.
For example, on Australian roads there are “CREST” and “DIP” warning signs, described as follows to learner drivers:
DIP: A sharp depression in the road can bottom out your suspension in extreme cases... It may also conceal other vehicles coming towards you so take care if you want to overtake another vehicle.
CREST: There’s a crest of a hill ahead. Be careful if you are overtaking as you might not be able to see vehicles coming towards you that are on the other side of the crest.
You’ll find the technical terms in use here.