Okay, so I believe I have a model that can detect which obstacles are most problematic. It uses the same information before but runs a few checks:
1) It checks to see if the tx - ty is close to zero ( so if the obstacles are going to cross the axes at roughly the same time )
2) Are tx and ty > 0 ? If there is a positive time of collision ( since the algorithm can give a negative collision time ) then it's a problem
3) Check the distance. It sees how close the obstacle is and if it's within a certain range, it's problematic.

TODO: include 3rd dimension