‘Safe’ is unrealistic. However, you can make it survivable with a little bit of planning. If you are sitting in the left seat, wait until the car is travelling around a bend to the right, so you will be thrown clear of the car. Make sure there are no oncoming signposts.
To protect your elbows, stuff your sleeves with paper or anything you can find. Crouch in the footwell, facing the door. Push the door open and jump out at a 45° angle. Pull your elbows in and put your fists under your chin. Keep your legs together and don’t try to land on your feet.
Aim to land on your back. This is the widest part of the body and will spread the impact force most evenly. Keep your limbs and neck tensed to prevent them flailing, and allow your body to roll. Resist the urge to put your hands out, otherwise you will break your wrists.