I do a lot of walking and taking the bus. Here is what I like in a bag: a pocket for a water bottle, an inner pocket to put some little, easily misplaced items, handles long enough to go over my shoulder, and a key ring which should be also on the inside. My everyday bag also has a whistle attached. People will stop and pay attention if you blow a whistle.
When I make them for other people, I make it with two sets of handles, one set for over the shoulder and one set for carrying it in my hand. I'm short and totally get what oogyda said about the length of the handles.
If you are making them to be the "fold up and store in your purse or pocket" type, then you don't need all the bells and whistles I mentioned.
I was going to post this. We have several bags with a pair of short handles, for arm's length carrying and a pair of long handles to sling over the shoulder. We tend to carry them as a shoulder bag until too laden, then use the short handles once it is
full.
I have a bag that I bought from a charity shop (some initiative to do with the Duke of Cornwall??), that is basically two panels of curtain fabric sewn together with French seams, with a short handle sewn into each side of the top hem. It fold into quarters and lives with all the other reusable bags in the over-the-shoulder bag-of-bags*, and is incredibly useful because of how strong the curtain fabric is. It's about four-six times [when folded] the size of those very fine fold-away nylon bags, but the handles have never shown any signs of wear [unlike the nylon ones!].
Having said that, the nylon ones are very useful to tuck a couple into a handbag for those impulse purchases.
Runningstar, I suspect you're going to have a lot of fun! As we all know, it's not self-indulgence if it's research.
* Why yes, I may be
some kind of bag lady.