“Head north. Really, that’s what it turns into. They should go until they feel safe, it’s up to them,” he said.

Shepherd said gas stations along the evacuation routes have been keeping a “wet system”, meaning they have been refueled to ensure they have enough gas for drivers. But don’t wait to fill up, he said.

“Tomorrow (Sunday) morning is no time to look for a (gas) station. Traffic is already starting to back up on evacuation routes,” he said.

But for those who don’t leave, Sgt. Ken Carona of the Port Arthur Police Department has a message.

“There will come a point when people have no police or fire protection, no medical staff for those who decide to stay after the mandatory evacuation is called,” Carona warned. “If we (police, fire, medical) have to leave, we leave. We can’t drag you from your home and make you go, but know that there’s no safety net. If you’re injured, you’re on your own.”

When officials do come back into town after the storm passes, their first task will be to secure the city and set up an infrastructure — not check on people who chose to stay behind.

“I urge people to just go ahead and leave,” he said. “If you want to be safe and be able to sleep, go ahead and get out of town. Think of this as an excellent drill.”

Carona said the fact is that officials simply do not know what Gustav will do over the next few days, making preparations more difficult.

“That is the biggest and hardest thing. There’s no perfect crystal ball. How strong and when Gustav will hit, we can’t tell. It’s a difficult thing to do,” Carona said.

Carona said emergency officials are working to deal with either tropical storm force wind and rain or a 120 mph hurricane.

Video footage of evacuation routes can be found at http://traffic.houstontranstar.org/cctv/txdot/txdot_regional_camera_list.html?road=ih-10_east