How to turn all variables in a url into a nice url with .htaccess?

Question

I have a page with urls with lot of variables, for example: http://dev.resihop.nu/addtrip?from=stockholm&to=goteborg&when=2010-09-06&got_car=1

How do I make it so that it instead gets written like this:

http://dev.resihop.nu/addtrip/from/stockholm/to/goteborg/when/2010-09-06/got_car/1

extra awesome features! (I'd be really happy with an answer only on the stuff above) I want to be able to pass any variables(not just theese), and I want to be able to pass them in any order. Like this:

http://dev.resihop.nu/addtrip/to/goteborg/from/stockholm/when/2010-09-06/got_car/1

The variables also need to be able to be empty. They should render like this:

http://dev.resihop.nu/addtrip?from=stockholm&to=&when=2010-09-06&got_car=1 http://dev.resihop.nu/addtrip/from/stockholm/when/2010-09-06/got_car/1