Disabled parking placards used to be ubiquitous in Portland. Until very recently, the city provided unlimited free street parking to placard holders, estimated at a $2,000 annual value. Many cars bearing these placards would remain in prime spots for weeks or months without moving.

In some parts of the city, cars with placards would occupy 20 percent or more of the on-street parking. This generates traffic by causing other drivers to cruise for spots, and it makes curbside meter management less effective. Putting the right price on parking is tough when 20 percent of the spaces are free to some people.

Joseph Rose, the Oregonian’s transportation reporter, said he couldn’t help but feel like some drivers were pulling a fast one. “After a while, you get the unshakeable feeling that a lot of able-bodied commuters are getting their hands on disabled permits and scamming a compassionate city out of millions of dollars in parking revenue each year,” he wrote recently.

All the city needed to do to solve the problem, it turns out, was to start charging disabled placard holders to park. That took effect July 1. In an informal poll by the Oregonian, 74 percent of readers said they thought the new rules had increased the number of parking spaces available.

Disabled placard holders are now charged $2.40 for 90 minutes of parking. Those who violate the rule will be given two warnings and then fined $39. As of mid-July local officials reported only about 10 such tickets had been issued, but the policy seems to be having an impact.

“We have so much more parking,” enforcement officer J.C. Udey told the Oregonian. “It just goes to show the program is working.”

Portland’s case is promising for other cities struggling with the same problem. San Francisco is considering almost exactly the same intervention: eliminating free parking privileges for disabled placard holders. Raleigh, North Carolina, recently did something similar.