Here's another tip on how to be productive during your transit trips. Riin Gill, a vocal bike advocate and spinner (yarn, not stationary bikes!) in town, generously provides us with a few tips on managing transit-friendly knitting projects.
I always carry a small knitting project with me so I have something to do at lunch after I'm done eating, in doctors' waiting rooms, and yes, while I'm riding the bus. I can't read while I'm in motion unless I want to get sick, but I can knit with no problem.
Socks are the ideal project. They're small, they're easy to knit on autopilot, they're easy to shove in a bag with very little notice, and you really can't have too many socks. I keep my knitting project in a clear plastic cosmetic bag (I bought a clear bag before a recent flight figuring I'd get through the security checkpoint if the TSA agent could see what was in it and not have to paw through my things. It did actually speed things up). The main section contains my yarn and actual knitting. A smaller outer zippered section contains stitch markers, a darning needle, etc.
When I'm knitting on the bus, I leave the yarn in the bag and leave the bag in my backpack, only pulling out as much yarn at a time as I need. That way the yarn isn't going to fall on the floor and get dirty, or heaven forbid, roll down the length of the bus. Having the yarn contained like this, sometimes I even knit while I'm walking. That's the great thing about knitting socks -- unlike larger projects, there's hardly any weight pulling down, so they're absolutely portable.