Thanks for replying, Melinda. My analysis needs to separate the walking time and the transit time on train/bus. And due to the size of my data, I need to use Python command to do the Network Analysis instead of clicking on buttons on the menu.
When I tested the menu options (so that I can create my arcPy commend accordingly), I found that the output route file only provides values for "Total_PublicTransitTime" if I choose "Mode: Public trasnit time " in the "Travel Settings" banner in the Network Analysis. The output column "Total_walktime" will be "null". However, if I clicked on the blue
sum sign and check both "PublicTransitTime" and "WalkTime", the output file will give me the walk time I need. Is there anyway to include this option into the python command?