Final answer:
In traffic control, a yellow arrow is a signal to proceed with caution, alerting drivers that the green arrow is ending and they should be prepared to stop if it is safe to do so.
Step-by-step explanation:
In traffic control systems, lighted arrows can provide important signals for drivers making turns. A yellow arrow typically acts as a signal to proceed with caution. It indicates that the protection for a green arrow is ending, and if safe, drivers should prepare to complete their turns before the arrow transitions to red, which will require stopping. Therefore, if you see a yellow arrow, it means to slow down and be ready to stop unless you are so close to the intersection that you can't safely come to a stop.