What should you do when you can see the curb line of the side street through the front entrance door of a bus?

When you can see the curb line of the side street through the front entrance door of a bus, initiating the right turn is the appropriate action because it indicates that the bus is well-aligned with the intersection and is in a position to make the turn safely.

At this point, the bus driver has visibility of the area into which they are turning, which allows for a better assessment of the traffic conditions and potential obstacles, including pedestrians and other vehicles. This clear line of sight confirms that the driver is ready to execute the turn without obstruction.

Taking this action ensures that the turn is made efficiently and safely, as the driver can also anticipate using proper lane positioning and maintaining awareness of any other road users. It's important to note that checking for pedestrians and other vehicles, while also essential, is often part of the turning procedure rather than the immediate action when approaching the curb line with clear visibility.