They wear the company uniforms, drive trucks with the company logo and deliver packages to your door.

But the drivers for Moon-based FedEx Ground aren't working for FedEx; they're working for themselves.

FedEx is certainly not the only company to hire independent contractors. Yellow Cab in Pittsburgh uses the same system. It's an employment model that gives workers flexibility and rewards hard work while benefiting a company's bottom line, but also one that unions and labor groups complain allows a company to avoid paying for benefits or worker protections.

Marick Masters, a professor at the Katz School of Business at the University of Pittsburgh, said the independent contractor model is attractive to businesses because it saves about 30 percent of the cost of standard employees by eliminating the need to pay unemployment insurance, health insurance and workers' compensation.

"It's a way of keeping your work force and labor expenses leaner," he said.

Mr. Masters said it was interesting to compare drivers at UPS with the drivers at FedEx Ground. UPS, he said, keeps its costs down by regimenting a driver's day and instituting time saving measures.

"FedEx is really less militaristic than UPS," he said.

So, while UPS drivers are employees with benefits, the upside for the FedEx Ground drivers is that they have a measure of independence.

However, he said, "If push comes to shove, one of the primary reasons that [companies] do this is to avoid unionization."

It was the cost of hiring employees that pushed the cab companies to turn to independent contractors. Jamie Campolongo, the owner of Pittsburgh Transportation Group, which includes the local cab companies, said the whole industry shifted to the model of independent contractors in the 1970s and 1980s.

He said not having employees saved the company money on Social Security and even more so on workers' compensation insurance, which he said made classifying the drivers as employees "cost prohibitive."

As independent operators, Mr. Campolongo said, the drivers are encouraged to develop their own clientele while still making runs for the company.

Rebecca Smith, a coordinator for National Employment Law Project, said the use of independent contractors has been growing in such industries as construction and janitorial services.

"Genuine independent contractors constitute a small portion of the American work force, because by definition, an independent contractor is a person who is in business for him or herself," Ms. Smith said in testimony presented to Congress in May. "True independent contractors have specialized skill, invest capital in their business and perform a service that is not part of the receiving firm's overall business. Most workers in labor-intensive and low-paying jobs are not operating a business of their own."

FedEx, which is facing a class-action suit on the classification of its workers, is not the first large company to be criticized for its use of independent contractors. Microsoft settled a lawsuit in the 1990s for $97 million over the issue and agreed to reclassify its workers.

The FedEx model is to sell routes to drivers. The delivery person has to purchase a truck, wear the company uniform and deliver the packages for FedEx, but he or she owns the route.

FedEx did not return phone calls seeking comment for this article.

Annette Craig, of King of Prussia, Montgomery County, found out she was not eligible for workers' compensation after she was hit by a car on Oct. 6, 2006, while delivering a package for FedEx. She said the company terminated her contract on Nov. 27.

The truck she had to buy to get the job was financed through FedEx, and it was then repossessed by the company. Now she is staying with a cousin and at friends' homes, essentially homeless, while her daughter lives with family in Florida.

Ms. Craig said she worked 16 to 18 hours a day on a route that included some of the high-crime neighborhoods of Philadelphia. She did not earn overtime, however, because she was an independent contractor.

Mary Beth Maxwell, the executive director of American Rights at Work, which issued a report on the issue of independent contractors at FedEx Ground, said the company had 15,000 independent contractors who should be classified as employees.

"They are employees; they are just employees without their rights," she said.

She said before her group and the Leadership Conference on Civil Rights began looking at the issue of independent contractors, she did not know about the issue with the FedEx drivers.

"We still have so much work to do to get this story out," she said. "And when we do, people absolutely do not think this is OK."