At night, Alfreta Bonds is a potential prisoner in her own home.

Bonds, a 19-year-old student at a business college here, is afraid to go out alone after dark. She does not own a car and can't afford cab rides. It's a lonely walk down a dimly lit street to the nearest bus stop.

Late last year, 21 rapes in two months were reported in Madison. And those were only the assaults that authorities know about. Alfreta Bonds does not want to become one of those statistics. But then again, she does not want danger and fear to keep her in her apartment every night.

Fortunately for Bonds and hundreds of other women in Wisconsin's capital city, there is a solution to this dilemma. It's called the Women's Transit Authority, a free transportation service designed to provide mobility and safety for women.

When Bonds wanted to go across town to study at a friend's house, as she did recently, all she had to do was call a transit authority dispatcher. Within the hour a white sedan pulled up to her apartment, Bonds got in, and the car whisked her 20 minutes across town to her destination -- free of charge.

"If I didn't have it (the transit authority), I probably would end up spending the nights just staying at home," said the young woman, who uses the transportation service about four nights a week.

The transit authority's three cars, lent by the University of Wisconsin motor pool, provide rides for between 50 and 75 women a night. Surveys show that 95 percent of the riders earn less than $4,000 a year. Half the riders are students. Many have low-paying night jobs in such places as hospitals and restaurants.

"There are some women who really need us," said dispatcher Laurie Mayberry, 22, one of the approximately 90 volunteers who operate the service. "They would not be able to go to work or make it home because they don't have the money for a cab or a car."

The idea for the transportation service came from a 1973 conference at which several Madison women's groups discussed ways to fight the problem of sexual assaults.

Women used their own cars at first but eventually the university stepped in to provide vehicles and insurance coverage.

Despite the university aid, the transit group prides itself on being a community service. It provides rides for women of all ages and is heavily depended on by the elderly. Of its $33,000 annual operating budget, only $12,000 is provided by the university, with $15,000 coming from the city of Madison and $6,000 from Dane County. The service operates every night from 7 p.m. to 2 a.m. Volunteer drivers or dispatchers usually work a three-hour or four-hour shift one night a week.

There are a few restrictions, however. Except in emergency situations, transit authority cars operate only within a four-mile radius of the Wisconsin state capitol, which is about five blocks east of the university campus.

The drivers are instructed not to pick up women traveling in groups of three or more; it is assumed that they are safe because they are in a group.

And, the service is strictly women only. Drivers, dispatchers and riders are all women. Men are allowed to do some daytime office or publicity work for the organization if they wish to, but when the sun goes down, the men are out.

Marianne Morton, one of three parttime paid staff members responsible for coordinating the volunteer shifts, acknowledged that many men had complained about being excluded.

"But women have been excluded all their lives," she said. Besides helping women overcome a feeling that they do not have to be dependent on men for their safety, Morton, 26, said, it would be self-defeating for the service to use men as volunteers. Female riders might fear for their safety if a strange male driver picked them up, she explained, or male dispatchers might keep phone numbers and addresses and harass women later.

The service goes through elaborate procedures to ensure the safety of its riders. To thwart potential attackers who might be eavesdropping on the transit authority's citizens band radio frequency, the dispatchers at first call in only the general vicinity of a pickup point to a driver. When the driver reaches the area, she radios back to the dispatcher, who then gives her the exact address. The dispatcher then telephones the rider and tells her to be ready to be picked up.

It can take an hour or more for riders to be picked up after they call the dispatcher. Some riders complain about the delay, but transit authority workers point out that they are not operating a cab service.

Most of the riders accept the delays and are openly appreciative of the service, dispatcher Mayberry said.