"Highway 24" is not really a highway, like an interstate type road. Locals call it "Telegraph", not 24. It is a very busy and heavily traveled road, especially in that area, on most days. There is a lot of traffic because it connects so many different cities, without having to take the city roads-with many stops/lights- or freeways. My family lives up there and once you get off a major freeway, you are taking roads to navigate around all the lakes or driving through a town. Both of which slow down your commute and are heavily traveled.
I don't really know how to explain it best for people not in the area but I hate driving up there because of all of the traffic and 'back roads' to get places. But it is not "back roads" like in the country. My aunt lives about 25 minutes from me but it took me almost 50+ minutes to get to their house because once I got off "24", I had to take several other roads to get to her place around the lakes. Although 24 does have traffic lights that slow people down, in addition to the heavy traffic, it is mostly a straight shot to get you close to where you need to be. Other family members actually prefer to take 24/Telegraph, over 275 and 75.
Of course other locals may not agree completely, but that is my view of it. For what it's worth..