What color indicates that a driver cannot travel when using a lane control signal?

The color red in a lane control signal specifically indicates that a driver cannot travel in that lane. This is a universal traffic signal that communicates to drivers that the lane is closed to traffic, and they must either change lanes or avoid that specific lane altogether. The red light serves as a clear visual command, ensuring safety by preventing access to areas that may be hazardous or where a stoppage is required.

In contrast, other colors serve different purposes; for example, green indicates that the lane is available for use, yellow serves as a warning or caution to prepare for a potential change, and blue is typically reserved for indicating accessible parking or services rather than lane use. Understanding these signals is crucial for maintaining effective and safe traffic flow.