As you are driving, the Tesla does the following:
When you leave the range of all known chargers, the car warns you. It could be that you know of a new charger the car hasn't visited, but it warns you that you are leaving the area with known chargers.
If you are navigating to a destination, the car will know remaining range and distance to your end point. You are often coming from a SuperCharger and going to the next SuperCharger. If your energy usage is significantly higher than expected while you are close to the last SuperCharger, the Tesla will direct you to return to it to charge further.
If you are approaching your destination and low on range, the Tesla will recommend a specific speed reduction to ensure you reach your destination. For example, it might recommend driving 65 mph instead of 75 mph. It will remind you again every few minutes. It will also update the speed recommendation as needed. These warnings are very hard to ignore.
As the range gets below 10% remaining, the battery symbol turns yellow and then red.
If you run out of charge on the road, it will be in spite of the best efforts of the car. You have to ignore a significant number of warnings. The kind of warnings that get your attention. Things like chimes, yellow exclamation points on the driver cluster and yellow border pop ups on the main screen.