"T" at end of photosensor line...

Does anyone know how long the “T” at the end of the photosensing lines for autonomous are? If you aren’t sure what I mean, I can edit a picture to show you just what I mean.
Also, is there a specific zone you can’t go into in autonomous? If so can anyone think of a way to use photosensors to stop from going in there?
Thanks in advance, Imran.

the “T” is 4 in deep and 14 in wide. also, you can’t cross over the center line to the opposing alliance’s side, and I would imagine you can’t go in their lanes ether.

cd5696 is correct. You may want to look at The 2011 Arena Layout and Marking drawing (pdf) FE-00034 Detail G