Aggree with JoolsMcFly. I would check what $transportation->transportable() returns. If it is a relational model, it may not be able to get the related data.

Looks like transportable() is supposed to return a morphed relationship. I don't think it is possible to declare the morphed model from the Transportation's side of view, because it doesn't know what kind of ride or whatever other class it is supposed to morph to yet. Sounds weird, but anyway:

Maybe try to save the Transportation from the Ride's side of view:

$transportation = new Transportation;
$transportation = $ride->transportations()->save($transportation);