The M45 is a spur from the M1 in Northamptonshire, westward towards Coventry. Today it just provides access to part of Coventry from one direction on the M1, but its historical significance is much greater.
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!