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SYLOH t1_iy71y9s wrote

It's mainly because most features are relatively level.
We don't really have many problems making a ramp.
We build them to connect surface and elevated highways/roads all the time.


breckenridgeback t1_iy7hz2f wrote

> It's mainly because most features are relatively level.

If you're building a bridge you are by nature probably not dealing with level terrain.


SYLOH t1_iy7i27f wrote

The sides of what you're bridging probably are.


breckenridgeback t1_iy7jb8x wrote

Often, but not at all always unless you intentionally build it that way.

The Golden Gate Bridge, for example, extends from a hill on the northern end of San Francisco (elevation a little over 200 feet) to rugged high hills/low mountains on the southern end of Marin County (which top out at 800-1000 feet). To make it level, it has to target a specific spot on the Marin coastline, then go through a tunnel.


SYLOH t1_iy7kiyd wrote

Maybe a bridge constructed in the 1930s had such limitations.
But modern suspension bridges often are built tall enough for ships to pass under, with ramps that get that high on either end. They don't really care if the height change on the ramp has to be small or large on one or both ends.