The first alarm indicating trouble in the city's Emergency Medical Services Bureau was sounded in February, when a Post-Gazette analysis determined that one-fourth of the pay earned by paramedics was the result of working beyond a typical eight-hour day.

The pervasive use of overtime suggested that staffing levels were inadequate, and a second bell rang out the same message last week in an audit released by city Controller Michael Lamb.

The national standard for ambulance response time is under nine minutes, 90 percent of the time. Mr. Lamb's auditors found that in Pittsburgh last year, just 60.4 percent of the city's ambulance runs met that goal. And that was worse than the rate of 64.5 percent in 2006. Even EMS Chief Robert McCaughan agreed that response times are a concern.

The average city ambulance went on 4,904 calls last year, significantly more than the recommended range of 2,500 to 3,000. One of the city's units went on 5,588 trips.

The solution proposed by the audit is straightforward: Make more ambulance crews available, particularly during peak usage times of 10 a.m. to 6 p.m. Mr. Lamb recommended the city study the feasibility of adding six to 12 more medics to its budgeted level of 163, which would result in at least two more ambulances on the street.

He also wants to develop a public awareness campaign in conjunction with hospitals and health insurers in an effort to reduce the number of unnecessary calls for ambulance services. That doesn't mean denying needed service; it means cutting down on unnecessary calls so residents who really need an ambulance are the ones who get one, and quickly.

The audit did not mention the possibility of merging EMS with the city's Fire Bureau, an issue under study by a Virginia-based firm that is expected to release its report late this month.

It may be too soon to identify a remedy, but the information in this audit should help find a cost-effective way to deliver this crucial public service.