Interesting question!

Certainly the "example track" is one of the tested tracks, so you need to be able to pass that one.

The + is a valid crossing here because (when going to/from the /) it is treated same as if it was a |)

Also, the requirement is not quite as you wrote:

wrong:

            /
           /
          / 
    -----+------
         |
         |

right:

           /
          /
         / 
    -----+------
         |
         |

Do you think this is sufficiently confusing that I should add more examples to the way crossings are described?

(I'm really suprised nobody ever asked this question before)