Activator rails do not eject mobs or players

Keen to test out activator rails i setup a simple circular test track in single player with two activator rails (one powered, one not) spaced a few rails apart.

I placed minecarts with mobs in them on the track and set them looping, as the carts pass the activator rails neither rail ejected the mob. This also did not work when i sat in the minecart.

You can view video of this issue here:
https://www.youtube.com/watch?v=RMCjhM_rz1U&feature=youtu.be