With a new decree from the Massachusetts Board of Public Health, state hospitals will no longer be allowed to turn away ambulances because of full emergency rooms starting in January. In Boston, where hospital crowding is often the worst, this new law may actually have the least effect. The idea is still a sound one and should improve the overall treatment of those who need it — in and out of the city.

The change was prompted by a rise in crowded ERs, particularly at bigger hospitals like Massachusetts General Hospital. Under the current system, an incoming ambulance with a patient would radio to dispatchers and ask to go to the closest hospital. If the hospital is unable to accept a new patient, the ambulance would be diverted to a less crowded facility.

For urban areas, the distance between hospitals could be separated by just a five-minute drive. And, except for the most serious conditions, the ride wouldn’t affect the patient’s health too severely. In the case of such critical patients, the nearest hospital would always make room. For suburban Massachusetts, however, the distance between hospitals is much greater.

So the new law forces the ER doors to stay open at all hospitals, but it doesn’t address exactly how hospitals will deal with a shortage of beds. Perhaps rules changing the way people use hospitals is the answer.

According to hospital officials, many patients use ERs for situations that would be normally be handled by a non-emergency primary care physician. This practice is reportedly increased under the commonwealth’s new mandatory health care laws, which cover emergency room visits more completely than some regular doctors.

Hopefully, the 2009 ban on hospital diversion will prompt hospitals to be more strict about admittance. Those who are not in an emergency situation should not be crowding ERs, preventing those who need urgent care from receiving it.