Shoulder (road) Puns

I'm in the back seat of my dad's car, as we're driving down a rather busy street of a populated city. My dad taps me on the shoulder and gestures out the window with an air of disgust.

Dad: "I can't believe all the political advertising they have out here."

I look around for quite some time, expecting to spot a house covered with election signs or political party banners. All that I see are a series of pylons with road signs intermittently placed in between them.

The signs say: "Keep left."

My dad snickers with pride and drives off.