If you’ve ever wondered why you have to wait so long for a bus in Staten Island, Brooklyn, or the Bronx, you should read Wednesday’s new report on the Family and Medical Leave Act from the U.S. Department of Labor.

The Family and Medical Leave Act of 1993 entitles employees of firms with at least 50 workers to 12 weeks of unpaid leave a year for the birth or adoption of a child, to cover a worker’s sickness, or to take care of close relatives with serious health conditions.

The Labor Department reports that the family part of the law is working fine, with employers organizing coverage for predictable time that parents spend with newborns. But the medical part of the law is being abused in some firms all over the country, with workers faking chronic illnesses or those of their relatives and leaving other workers to cover for them.

Among those who submitted comments to the Labor Department was the executive assistant general counsel to the New York City Transit Authority, Florence Dean. She writes that “NYCTA has certain bus depots where upwards of 8 or 9 percent of the bus operators have submitted doctor certifications claiming entitlement to intermittent leave for a variety of aches and pains or self-reported complaints.”

In Staten Island, 17% of bus operators were approved for FMLA leave in 2006. Brooklyn and the Bronx did better, with 8% and 9% of bus operators respectively. It is highly unlikely that bus operators and their families within the same city have such disparate, poor medical histories. This experience is typical of other large cities, such as Philadelphia.

Waiting for buses is inconvenient, but unanswered 911 calls are downright dangerous. A counselor to Mayor Bloomberg, Anthony Crowell, wrote that the police communication technicians who handle New York’s 911 Emergency Call Center have unusually high rates of FMLA leave. In February 2007, 32% of call-takers were approved for FMLA leave. FMLA accounted for 27% of all medical leave taken in 2006.

According to Mr. Crowell, “If the City did not have the ability to order PCTs to work overtime, the 911 emergency response system in New York City would be severely compromised.”

It takes just one certificate from a doctor saying that a worker — or his relative — has a chronic condition, such as back pain or asthma.

This document is the only thing workers need in order to get 12 weeks of unscheduled, intermittent leave without even additional medical visits. Under Labor Department regulations, employers have to be notified only two days afterwards if workers have taken FMLA-covered leave. So workers can simply not show up for work, and then call in two days later to inform employers about their condition.

Leave can be taken all at once, that is the entire 12 weeks, or piecemeal, a few hours or days at a time. Therefore, workers with medical certificates on file can arrive at work two or three hours late, and chalk their absences up to FMLA-covered leave. The employer has no grounds on which to fire them or even to give a negative performance rating.

As might be expected, the Labor Department received numerous letters saying that this system defies common sense and is unbalanced. The employer loses the ability to discipline workers who take FMLA around holidays and weekends.

Mr. Crowell reported that “the inordinate number of employees who call in sick for allegedly FMLA qualifying reasons on holidays, sick days, and during public emergencies, speaks volumes as to how the FMLA diminishes the rights of the employer.” A portion of the New York Police Department’s $3.6 million overtime costs in 2006, up from $1 million in 2002, can be attributed to FMLA leave.

The Labor Department believes that 6 to 13 million workers are likely to use FMLA leave. These workers are disproportionately concentrated in certain workplaces, and make life miserable for their coworkers.

Verizon reported that 44% of workers in its Florida network centers and 42% in its business solutions group had FMLA certificates.

Without changes in the Department’s regulations, the situation is likely to get worse. As the workforce ages and the “sandwich generation” — responsible for looking after both children and elderly parents — grows, more workers might misuse FMLA. The increasing prevalence of businesses that remain open 24/7 also tempts employees to try to shift the burden onto coworkers.

Some simple changes in regulations could discourage abuse of FMLA. Employers could require workers to inform employers on the day they take leave, rather than two days later. In the case of repeated, intermittent leave, employers could be allowed to ask workers for additional proof of sickness, beyond the initial certification.

Finally, employers could be permitted to use incentives to control absences and encourage punctual arrival at work.

Rather than encouraging the Labor Department to move in this direction, Congress is doing precisely the opposite. Senator Kennedy has proposed “The Healthy Families Act,” which would require employers with 15 or more workers to offer seven days paid sick leave. The sick leave could be taken in “the smallest increment that the employer’s payroll system uses to account for absences.” That would extend the intermittent leave problem to millions of small firms.

The next time your bus is unusually late, ask the driver whether she’s covering for a “sick” coworker. She might well say yes.

Ms. Furchtgott-Roth, former chief economist at the U.S. Department of Labor, is a senior fellow at the Hudson Institute.