Originally, CN GP9s had high short and long hoods and most were set up to run long hood forward (controls on right hand side with long hood pointing forward). The CN GP9s in service later (model GP9RM) were rebuilt from older GP9s. In the process of rebuilding, the high short hood has been reduced in height to give visibility from the cab over it. Most, although not all, were equipped with cylindrical horizontal spark arrestors on the exhausts; in the photos above.
The GP9RMs were in four groups:
4000-4036: These locomotives were used to pull trains generally on the lower traffic branch lines. They were restricted in the amount of fuel they carry and this reduces their weight. They were not certified for operation in the U.S. They were painted in the CN black and white zebra stripes with a black cab. The control stands were changed to facilitate short hood forward operations.
4100-4143: These look the same as the 4000 series but can carry more fuel. This made them heavier. They were certified to operate in the U.S. Control stands were changed for short hood forward operations.
7000-7083: These were used as yard switchers. Most were painted in the CN noodle and black cab although some had the newest CN paint scheme (CN noodle and one stripe). They retain the long hood forward orientation of the controls. Some were equipped for remote control operation.
7200-7280: These are used as mothers for slugs for low speed switching operations. Most are equipped for remote control operation and inside control stands are set up for long hood forward operation. Some are certified to operate in the U.S.