Tricycles produced by Kien Tuong wheelchair factory in Saigon, used instead of wheelchairs by people with some ability to walk or crawl when indoors. I'm pretty sure the design originated in West Africa (there is a book by Handicap International trainer Philippe Mazard describing how to build something similar). Kien Tuong has made many local modifications and improvements and there are thousands of these around Saigon. video at http://www.youtube.com/watch?v=pgIBgNWdShQ