Road Liable To Subsidence

I was getting the hang of it by now and decided to keep my eye on the ground for any other hazards along the way. Unfortunately this meant that I cracked my skull on the overhanging sign that said:

Recession Round The Corner
Keep Your Head Down

Well, my head rolled, along with a few thousand others. Still, not to worry. I'd learned a lot from my mistakes.
I had my wits about me now. Pushing sixty. Surely nothing could surprise me at this stage? A SatNav-like voice in my head told me not to worry and just keep cruising. Then I spotted something on the horizon. It looked like a huge milestone. Nobody could miss that...