Simply define the fields; What the problems?
In Route entity
/**
* @var string
*
* @ORM\OneToOne(targetEntity="Position", cascade={"all"})
* @ORM\JoinColumn(name="start_position_id", referencedColumnName="id")
*/
private $answerRight;
/**
* @var string
*
* @ORM\OneToOne(targetEntity="Position", cascade={"all"})
* @ORM\JoinColumn(name="end_position_id", referencedColumnName="id")
*/
private $answerWrong;
And in Position entity:
/**
* @ORM\OneToOne(targetEntity="Route")
*/
private $route;