Harvard, NYU, and NEJM researchers draw on traffic engineering to explain why more physicians per capita is linked to longer waits .
A new analysis published in NEJM Catalyst Innovations in Care Delivery finds that the standard response to growing specialist wait times, hiring more physicians, is unlikely to solve the problem on its own, and may even worsen it. The article, Reducing Specialist Wait Times: What Can We Learn from Highway Traffic Engineers?, draws a direct parallel between specialist scheduling and highway congestion, where adding lanes fails to ease traffic because drivers simply adjust their behavior to take advantage of the new capacity.
Wait times for new specialist appointments in the United States have been rising for two decades. A national survey of six specialties across 15 metropolitan areas found that average wait times reached 31 days in 2025, up 19% since 2022 and 48% since 2004. Longer waits carry real costs for patients, including psychological strain and, in some cases, worsening symptoms that lead to more hospitalizations and emergency department visits.
Key Findings
Examining wait-time and physician-density data across four referral specialties — cardiology, dermatology, obstetrics-gynecology, and orthopedic surgery — the authors found positive association between the number of specialists per capita in a metro area and how long patients waited for an appointment.
The authors describe that this pattern mirrors “induced demand” in transportation economics: when road capacity increases, people drive more, quickly eroding any gains in travel time. In specialty care, the analogous dynamic is that more available specialists can lower the threshold at which primary care physicians refer patients, encourage patients to seek specialty care more readily, and lead specialists themselves to manage issues that primary care could otherwise handle. The result, the authors write, is that new specialists’ schedules fill quickly and wait times fail to fall.
Rather than relying primarily on hiring, the authors outline three categories of tactics, adapted from how traffic engineers manage congestion, that health systems can use instead or in tandem:
- Expanding care options, such as building guidance into electronic health records so primary care physicians can manage more conditions themselves, expanding physician assistants’ and nurse practitioners’ role in specialty care, and offering virtual group visits to cut wait times.
- Adjusting financial incentives, including raising copayments for specialist visits relative to primary care, and reduced out-of-pocket costs for chronic disease care delivered by nurse and other provider teams.
- Giving patients better information tools, such as online self-scheduling, which reduces no-show rates and helps keep physician schedules full, and implementation of AI to answer patient questions and flag developing problems before they require a specialist visit.
The authors caution that redesigning specialty care is difficult: seeing long-stable patients is often easier for specialists than taking on new, complex cases, and any redesign has to give specialists the support they need to handle the patients who most need their expertise.
“Our argument is not against hiring more physicians, but for better leveraging the clinicians we have,” the authors write, adding that advanced practice providers in particular are “perpetually overlooked” in care redesign despite their central role on care teams.