The Rental Car Association in Samoa says a switch to driving to the left side of the road would ruin many businesses.
The Transport Control Board has proposed that road users end driving on the right as has been the convention since the German colonisation.
If the switch goes ahead, it will happen in the middle of next year.
The issue has sparked some protest in the business community.
The president of the Rental Car Association, Roy Lee, says the switch would be too costly for many rental car companies.
"What they are planning to do without any consultation is putting ourselves into a very vulnerable situation. Bear in mind that most of the vehicles are leased or on long-term lease for five years. And at the end of that term all those vehicles will be worthless, nobody would want to buy them."
Roy Lee says the government needs to consult businesspeople and the general public, and outline its plans better.