How do highway engineers choose between over/underpasses for interchanges?

[kphoger]

it just would look impressive

Side question:  how important is "would look impressive" in the decision-making process?

[architect77]

it just would look impressive

Side question:  how important is "would look impressive" in the decision-making process?

It's not important to me as I know how underfunded states are in replacing infrastructure as so much of it reaches the end of its initial service life.

Civil engineers do span a range of styles though as I've driven through about 37 states and they all look visibly different in how their overpasses, underpasses, signage and level of quality are concerned.

One negative aspect I see is that the availability of precast concrete beams/girders for flyovers has resulted in using curved bent exposed steel on under curved portions of flyovers and the rest using precast concrete and the resulting hodgepodge appearance lacks the elegance of continuous matching materials.

[kernals12]

It looks like the Miami area almost exclusively uses overpasses for freeways instead of underpasses. I'm guessing that's because there are lots of waterways that need bridges anyways.

It's also flat and I'd also wonder about drainage and the water table.

water table is definitely important in Florida

[LilianaUwU]

idk the engineers just go with how they feel that day or something

[kernals12]

If the issue was solely aesthetics then ADOT made some weird choices in putting I-10 below grade as it passes  by the industrial areas near Sky Harbor Airport while putting Loop 101 on an elevated grade through the upscale areas of North Scottsdale. Because of that, I'm going to believe what they told me that below grade is cheaper as well as safer and above grade is only worth it when flooding is a concern. That would also explain why Tempe would tolerate the Red Mountain Freeway being above grade as it passes by Tempe Town Lake.

[CoreySamson]

Texas is converting a lot of their underpasses on their freeway interchanges to overpasses when they rebuild or widen the freeway. One big example of this happening right now is I-10 between Winnie and Beaumont. I think that they are doing this because doing an overpass generally fits better with the U-turn feeder road system and ultimately takes up less space.