What does a solid white line between lanes mean?

A solid white line between lanes indicates that drivers should stay in their lane unless it is necessary to change. This line serves as a guide that discourages lane changes, promoting safety and stability on the road. It signals to drivers that while lane changes are not prohibited, they should be done with caution and only when absolutely required, such as to make a turn or avoid an obstacle. This helps to minimize the risk of accidents caused by unexpected lane changes, ensuring smoother traffic flow and better communication among drivers.

In contrast, options that suggest lane changes are either encouraged or mandatory do not align with the purpose of the solid white line, which reinforces the importance of maintaining lane discipline for all road users.