Activate a Camera viewport. >Viewport navigation controls > Truck Camera
Trucking a camera
Truck Camera moves the camera (and its target) parallel to the view plane.
This button replaces the Pan button when a Camera viewport is active.
For a target camera, dragging the mouse moves the locked camera and its target parallel to the Camera view. For a free camera, dragging the mouse moves the camera along its XY-axis.
Procedure
To constrain trucking of any viewport to a single axis, hold down the SHIFT key. The truck is constrained to the first axis you move while the SHIFT key is down.
To accelerate trucking, hold down the CTRL key.
To truck a camera:
Activate a Camera viewport.
Click Truck Camera.
The button turns green when it is on.
Drag to move the camera and its target.
The camera and its target move parallel to the view plane, which is perpendicular to the camera's line of sight.
Press ESC or right-click to turn off the button.
To constrain trucking to a single axis:
Hold down the SHIFT key.
The truck is constrained to the first axis you use.