Get yourself a good, hard copy map. Mark the official evacuation routes. Try driving them if you can. Try alternate routes. See what is on those routes and what the road is like.

Use the acronym PACE:

Primary: The best plan to accomplish the mission (you have a place to go when you evacuate and a good route to get there).

Alternate: Still trying to accomplish the mission, but with some changes in routes and timing (maybe you have to wait for the traffic to die down or take another route).

Contingency: You may have to accomplish the mission by trying something else (in this case maybe you have to go to another evacuation location because you can't get to your primary).

Emergency: You can't leave and need to plan to hole up in place (this is survival mode and you need to ensure you can accomplish it by have the necessary supplies and equipment, and your location needs to be survivable).