Get any pod file utility capable of extracting files.
I'll use C-POD as an example because I am familiar with it, and there's a good set of tutorial pages for it that Phinny drew up.
Here's the download page for C-POD
http://ch.mtm2.com/c-pod/c-pod.php
Ok; so open up (with C-POD) the pod of the track you want to clone (TPark.pod for farm road 29) and <a href="http://ch.mtm2.com/c-pod/extract.php">extract all the files</a> from the pod to your project directory. That is: whatever folder holds the "art" and "models" folders for Traxx.
http://ch.mtm2.com/c-pod/extract.php
This will extract the art and models from the track to your art and models folders. Also, it will extract all the data required for cloning the track. It will make more subfolders such as "data", "world" etc. if they don't already exist.
Now open up Traxx and select File -> Clone Tracked Track. Then navigate the the "world" folder and select the SIT (situation) file of the track you wish to clone. Probably it's called TPARK.sit or something like that. It will be the only file in the "world" folder if this is your first time cloning a track.
Now you can save as TXX
and modify whatever you want. This is also a useful operation if you lose a txx of one of your own tracks.
Note to anyone reading this:
Please remember, if you modify somone elses track without getting permission and giving credit where credit is due you are likely to get lots of people very angry with you.
Just don't be a jerk.
Treat others how you wish to be treated.