Guerrilla Signage: This Way to 422

Someone has taken it upon him- or herself to add an unofficial traffic sign at the intersection of East Swedesford and Valley Forge roads, near Gateway Shopping Center.

The sign simply says "422 W" above an arrow pointing under Route 202.

What do you think? Is this a helpful hint or an unnecessary eyesore? 

If you could add one new street sign, where would you put it?