A Metro Transit bus shrink-wrapped in hot pink is making the rounds this spring and attracting lots of attention, not surprisingly. But one Drive reader noticed it in St. Paul for another reason.

The rolling billboard sponsored by Planned Parenthood is emblazoned with a giant image of an intrauterine device (IUD), a flexible, plastic T-shaped device that's used to prevent pregnancy, and accompanied by the words "Birth Control, It's What We Do."

"This is concerning," the reader said in a voice mail. "I feel something that as a taxpayer service for St. Paul, Minneapolis or anybody who takes a bus ride, they should not be subjected to something where the bus system gets revenue to sell a service such as that."

The reader is not the only one to take issue with the advertisement. Metro Transit spokesman Howie Padilla said the agency has received a handful of complaints objecting to the ad.

Planned Parenthood says the rolling ad is a way to "get people fired up about the importance of high-quality reproductive and sexual health care."

For sure the ad, dubbed "the Birth Control Bus" by Planned Parenthood, touches on a controversial topic, but Padilla says it meets Metro Transit's policy of accepting advertisements for products and services.

"Planned Parenthood is a service," he said.

The ad, Planned Parenthood spokeswoman Jennifer Aulwes said, is not meant to be offensive. It's meant to be educational, and it's not all that different from how other health care providers have put ads on buses and light-rail trains and in bus shelters.

"We've seen a very positive response," Aulwes said, noting scores of tweets from supporters who have seen the bus. "They love seeing the pink bus."

As for the IUD, the image was chosen because it is the most effective pregnancy prevention available, Aulwes said.

"Ninety-nine percent of women use birth control at some time, so there is nothing objectionable about this basic type of health care that's accessed at some point," she said. "And we are the absolute experts in birth control."

Advertising is a big source of revenue for the state's largest public transportation system. In 2017, ads promoting everything from cellphones to art exhibits to local professional sport teams brought in $4.3 million. That's money sorely needed as the Met Council, which operates the system, grapples with a more than $100 million transportation deficit.

Transit advertising has reach, too. More than 290,000 commuters a day board Metro Transit vehicles. And thousands more see ads as buses and trains roll by.

Not every ad cuts the mustard. Metro Transit routinely declines those that don't meet its standards, Padilla said. The agency turns down issue-oriented ads, which is why you won't see ads for political candidates or hot-button topics.

The agency also declines ads for products and services that are illegal or encourage unlawful behavior. A legal product or service featuring a person hitting somebody with a wrench would be disqualified, too, Padilla said.

One that did qualify is "Eyes Off the Road ... Here ... Not There" from the Minnesota Safety Council, State Farm and Metro Transit. The new distracted driving campaign, urging drivers to put down their phones and keep their eyes on the road, comes as a bill to prohibit drivers from using hand-held devices got hung up at the Capitol.

Follow news about traffic and commuting at The Drive on startribune.com. Got traffic or transportation questions, or story ideas? E-mail drive@startribune.com, tweet @stribdrive or call Tim Harlow at 612-673-7768.