Its first section opened in 1973, and the rest was all built, but the A41(M) doesn't exist. It was canned in favour of orbital roadbuilding, and later resurrected in a more modest form.
If you've ever been on the M62 across the Pennines, you'll know the one. It's the huge arched bridge 120ft above the road. And this is what it's like when you're standing on top of it!