VICTORIA - The federal Transportation Safety Board has issued a safety advisory covering nine BC Ferries vessels a week after a loading accident sent a vehicle tumbling into the water.

The board is recommending the installation of warning alarms for ferries that use right-angle drive units used to help position the vessels in their berths.

BC Ferries says it's already committed to installing the audio-visual alarms after a similar incident four years ago.

The ferry MV Quinsam was loading vehicles at Nanaimo before a short sailing to nearby Gabriola Island on Jan. 9 when it suddenly backed away from the dock.

A pickup truck on the loading ramp tumbled into the harbour but the driver and sole occupant scrambled clear before his vehicle slid off the ramp.

In its preliminary review, the board says information so far indicates the Quinsam's stern right-angle drives may have suddenly rotated either because of some control-system malfunction or an inadvertent rotation of the control stick.

The board says it investigated a similar incident involving the ferry Bowen Queen while it was unloading vehicles at Gabriola Island in 2002.

In that case, the federal safety regulator found other BC Ferries vessels equipped with right-angle drives had a similar history of erratic behaviour.