When may a driver pass on the right of another vehicle?

Passing on the right of another vehicle is allowed when the vehicle ahead is making or about to make a left turn. This situation typically indicates that the vehicle is shifting into the left lane, thus creating an opportunity for the driver to proceed safely and legally to the right. It demonstrates the principle of making safe driving decisions based on the actions of other road users.

The other options, while they may seem reasonable at first glance, do not provide the specific legal context that justifies passing on the right. Simply having a clear road, no traffic, or a stationary vehicle does not inherently make it permissible to pass on the right, as these situations could present different hazards or legal considerations. Understanding when it is appropriate to pass on the right is crucial for the safety and regulation of traffic flow.