I switch around between walking, running, bicycling, motorcycling, and driving. I used to mix in some train rides but have not been doing that lately.
I find that my choice depends on my mood. This year I have been more contemplate so I am doing a lot of walking. The advantage of walking is that I must accept my limitations. No matter how much of a hurry I am in, I am only going to travel 3 or 4 miles (5-7 km) in an hour. That means it is going to take time to get where I am going.
Research and writing also take time. I may wake up in the morning with plans to finish certain tasks. I have grand visions. Then I need to step back and think about what is realistic. Research is slow. Writing well and accurately is slow.