Subaru 2002 Legacy Owner's Manual page 341

In case the trailer hitch connector or hitch ball should break or
become disconnected, the trailer could get loose and create a traffic
safety hazard.
For safety, always connect the towing vehicle and trailer with trailer
safety chains. Pass the chains crossing each other under the trailer
tongue to prevent the trailer from dropping onto the ground in case
the trailer tongue should disconnect from the hitch ball. Allow suffi-
cient slack in the chains taking tight-turn situations into account; how-
ever, be careful not to let them drag on the ground.
For more information about the safety chain connection, refer to the
instructions for your hitch and trailer.
n Side mirrors
After hitching a trailer to your vehicle, check that the standard side
mirrors provide a good rearward field of view without significant blind
spots. If significant blind spots occur with the vehicle's standard side
mirrors, use towing mirrors that conform with Federal, state/province
and/or other applicable regulations.
n Trailer lights
CAUTION
Direct splicing or other improper connection of trailer lights may
damage your vehicle's electrical system and cause a malfunction
of your vehicle's lighting system.
HB0085
Driving tips
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