Urban sketching on the go

I'm really enjoying these Pilot G-Tec pens for fast sketching on the go. They are not waterproof, like the Uni-Ball Vision, so adding watercolor is not a option. But why even add color? "There's a lot of color in black and white," I heard fellow sketcher Melanie Reim say once.

I did the 20-minute sketch on my mini pocket Moleskine notebook while waiting for my kids to get off school, looking out the side window from my little Chevy Prizm.