Rami Tabello of the non-profit Toronto Public Space Initiative says he believes the lighted advertisements are a blight on the cityscape.
"They're conspicuous, they're bright and our very own transportation services department has said that they're dangerous to drivers," he told CBC News.
But Blair Murdoch, whose company Allvision handles advertising for the provincial transportation agency Metrolinx, says the ads are a benefit to the city.
"The city will be receiving five per cent of the time on all of the signs for promoting city initiatives, citywide issues," he said.
Murdoch also said there is no proof the signs cause accidents.
The Canadian Automobile Association believes the city should allow the signs, then study their impact.
"I think it's important that city officials do monitor it to see if there is an increase in collision data, so that we can actually follow up in years to come," spokeswoman Faye Lyons said.
City council will also look at whether new, large signs should be on the sides of big buildings. Staff has recommended that council approve 20 spots across the city.
Tabello said he hopes council will reject the staff recommendations.
The signs "destroy a sense of place," he said. "They turn our streets into basically the equivalent of a mass market magazine."
Council is scheduled to debate the issue this week.