Which action should be taken first when securing a bus to leave it unattended?

When securing a bus to leave it unattended, the first action to take is to set the parking brake. This is crucial because engaging the parking brake prevents the bus from rolling or moving unintentionally, ensuring it remains stationary. By setting the parking brake first, you establish a primary safeguard against potential accidents and enhances safety.

After setting the parking brake, other necessary actions can be taken, such as turning off the ignition or taking the key with you, but the immediate priority is to secure the vehicle in place. Some actions, like putting the bus in neutral, could inadvertently allow the vehicle to roll if the parking brake is not engaged first.