A local advertising agency is reviving the idea of turning private cars into advertising billboards.

While the idea has failed in the past because few car owners were willing to use their cars to advertise products or services, local start-up Adogo claims it has no problems recruiting drivers and already has 1,000 signed up.

"Some of the drivers are Uber and GrabCar drivers," said Adogo managing director Max Lin. "We are now targeting advertisers more."

The ad agency, which was formed last November, said that 150 cars are already plying the roads carrying advertisements.

"The service meets the demands of advertisers and helps drivers earn passive income," said Mr Lin.

Advertisers pay Adogo $160 a month to advertise on the rear bumper and $280 to extend advertising to the doors.

Drivers get $50 a month for "renting out" the rear bumper space and $150 a month for the bumper and side doors.

Mr Lin said it is cheaper to advertise on cars than taxis, and that the agency's drivers clock at least 1,500km a month.

He added that advertising on cars is also more eye-catching. "When you see a private car with stickers, it captures your attention more than stickers on taxis. What was the last ad you saw on a taxi?" he said.

It costs $500 per month to advertise on taxis, according to rates published by Moove Media, a subsidiary of ComfortDelGro. Taxis are required by the Land Transport Authority (LTA) to travel at least 250km a day, or 7,500km a month.

Mr Lin said the agency's six clients - including a car workshop, a maid agency and a mall - bought between $15,000 and $120,000 worth of ads each.

Sales executive Calvin Wong, 34, who signed up with Adogo two months ago, receives $50 a month for carrying ads for car workshop ACMA Engineering Works and Trading on the rear bumper of his four-year-old Toyota Vitz hatchback. "People come up to me and ask if I own the company," he said.

Business owner Lionel Lee said he is not bothered by the image of his nine-year-old Honda Jazz being used as an advertising billboard.

"A car is just a tool to get from point A to point B," said the 23-year-old. "Besides, the ads pay for about three weeks of petrol."

But not all drivers are open to the idea. When The Straits Times polled 10 private car owners, eight rejected the idea outright, one was neutral and only one was willing.

"You are not kidding me, right?" said a lawyer who drives a Porsche and declined to be named. "I don't want people, including my clients, to think that I am a cheapskate."

Adogo said its services do not run foul of the law. "Everything we are doing is legal and approved," said Mr Lin.

LTA said it does not regulate the display of ads on private cars, but the driver has to ensure safety is not compromised by covering the headlights or signal lights, for instance. The stickers cannot be obscene or offend religious sensitivities, it added.

Police told The Straits Times that in 2011, they dropped a rule requiring vehicle owners to get approval before putting ads on their cars.

"The idea is good but private cars might not move around enough to give exposure and persuade potential advertisers to buy space," said editor Julian Kho of online car trading and news site sgcarmart.com.

"Incentivising drivers is a must. Petrol rebates are attractive to drivers - no one wants to pay full price for petrol," he added.