Just a few things,

I'm designing a bicycle trailer for urban based commuters for anyone who doesn't know. I've been sketching and surveying users (thanks to all who have given me responses!). Below are a few bag sketches. The bags will attach to a blank trailer and will accept up to several bags at once (one bag dosen't fill the entire thing). There will be three bag sizes, small, medium, large and each size will be customized for certain types of objects or tasks. For example, the small bags would be placed so they are easily reached and hold small, more valuable objects (wallets, keys, phone, iPod, babies). So far, I've just worked on the outer forms of the bags and haven't delved into the interiors yet.

A few small, upper bag ideas are what I present here.

This bag is more in the vein of the large bag, designed as a large cargo volume bag for carrying groceries for example. Basically anything big goes in here.

A few sketches on the over all form, these sketches in particular are only with two bags. The trailer would accept up to three small bags is my thinking for now.

After a tip from Shaun to check out push/pull golf bag carts I visited Miles of Golf and got the low down from the sales guy. Interesting things, pretty impressive how small they can fold up. I don't think I'll take allot from the carts in terms of holding the bags, but more from the structure and how they fold.