Having done all three activities while at UCSD, it’s an appropriate time to convey which kind of transportation means is the best for any given situation.
Walking obviously doesn’t result in the offset of any negative emissions on the environment. Busing results in some emissions, but obviously reduces the impact of each individual (dramatically making it more fuel efficient/environmentally friendly than driving directly.
Convenience & Speed
Driving most definitely gets you where you want to go the quickest. Busing can be hectic and super annoying (the wait), but at the same time is dramatically faster than walking.
If you want to get fit, walking is the way to go. Driving requires more effort than busing however, in providing your feet the ability to move back and forth. Busing requires virtually no effort at all.
There’s virtually no risk in walking (if you do it carefully). You will most likely not get run over walking. Driving has some risks associated with it (through encounters with drunk drivers or bad drivers of all natures). Busing has the most risks involved (putting your life in another’s hands, encounters with the homeless and gangs etc).
In terms of sight-seeing walking allows for you to encounter everyday activities more easily. Busing does to a certain extent (waiting at the bus stop, etc.), but driving does not (aside from looking outside the window).
In the end, walking wins the battle of good vs. evil. Choose your paths wisely.