I guess these ones at the Baillieston Interchange on the M8 just outside Glasgow are about as thick, but they're much shorter. Of course down south there at below 56°N the weather's a lot gentler and kinder.

https://goo.gl/maps/MD6ErnBZ4mzDdkup9

If you spin round to look west at the M73 flyover you'll see they're a kind of tapered oval section, but they're also forming a triangle with the road deck which makes the structure a lot stiffer.

I was surprised to discover how much concrete bends when I was doing radio comms work on the Queensferry Crossing project a bit north of Edinburgh. The road deck was built as steel sections with concrete on top and lifted into place, one side then the other. With them "unbalanced", one side lifted on but the other not lifted yet, the top of the 600-foot concrete towers - the top had a working platform about the size of four parking spaces - bent over by about six feet...