use Perl

Have a look at the strace output. man strace for more details. dtrace or truss on Solaris. dtrace or ktrace on Mac OSX

If the skybridge is charged for, then most low cost carriers opt for the bus. So even if there are a hundred skybridges free, you'll still be bussed.

The bike swapping scheme is cute, but will be difficult to implement, since arriving and departing passengers have to be separated. You'd have to make two separate streams suitable for bikes and a change over area that you can selectively lock for either stream. You'd also have to provide space for the people not able to ride bicycles.