Here is a brief list of your travelling options according to security status:

* Players with -2.0 or worse cannot enter 1.0 systems
* Players with -2.5 or worse cannot enter 0.9 systems
* Players with -3.0 or worse cannot enter 0.8 systems
* Players with -3.5 or worse cannot enter 0.7 systems
* Players with -4.0 or worse cannot enter 0.6 systems
* Players with -4.5 or worse cannot enter 0.5 systems