If you travel in a wheelchair, or care for someone who does, you might want to take a look at this website, run by the University of Michigan’s Transportation Research Institute. You’ll find recommendations for best practices, other suggestions, and detailed information about how to use tie-down straps and locking devices.
There’s also an “Other Factors” page with specifics covering basic information that otherwise might get learned the hard way. (Securing loose items, how to deal with trays, head and neck support, etc..)
Especially useful for those who are new to wheelchair transport, this website is also an excellent refresher course for the old pro. (Or for anyone relying on the incomprehensible leaflets that come with new straps.) A glossary page demystifies some of the jargon, and there’s a useful resources page, too.