When driving on the highway, once you are in your proper lane, you should...

Staying in the middle of the lane is the most effective choice when driving on the highway. This position allows for ample space between your vehicle and the edges of the lane, providing better control and safety. Being centered in your lane also gives you room to respond to any sudden obstacles or changes in traffic conditions, contributing to a safer driving experience.

Maintaining a central position within your lane helps prevent drifting, which can lead to accidents or unintentional lane changes. It allows for more balanced handling of your vehicle, especially at higher speeds typically found on highways. Furthermore, this positioning helps you easily gauge the distance to vehicles in adjacent lanes, assisting in safe lane changes if necessary.

The other options suggest staying too far to the left or right, which can increase the risk of collisions with vehicles in adjacent lanes or lead to running off the road. Frequently switching lanes is also not advisable, as it can create confusion for other drivers and increase the likelihood of accidents. Staying in the middle of your lane is thus the best practice for highway driving.