THE PROLIFERATION of affordable, convenient, curbside bus service along the Interstate 95 corridor, including the motorcoaches that run between the District and New York, has been a blessing for budget-conscious passengers. It has also been a cause for concern. In an industry that is generally underregulated — compared with domestic aviation, for example, which carries about the same number of passengers annually as buses do — there has been an opening for shady operators.

A report by the National Transportation Safety Board (NTSB) last fall found that, on average, curbside bus operators had higher rates of accidents, injuries and fatalities than conventional operators (such as Greyhound) or charter bus firms. While many curbside bus companies offered safe, responsible and reliable service, others drove up the average with relatively frequent violations of federal rules on unsafe driving, driver fitness and vehicle maintenance.

In recognition of that, regulators conducted a year-long investigation that culminated last week with what the Federal Motor Carrier Safety Administration (FMCSA) called the broadest crackdown on safety infractions in its history. The agency shuttered three main companies that oversaw a web of related curbside bus operators.

The investigation found an array of bad practices that suggested indifference to safety. Alarmingly, many of the curbside operators targeted in the federal probe had previously been ordered shut but had continued to operate, in many cases simply by changing names or bases of operation.

In its report last year, the NTSB described ripe conditions for bad actors to thrive in the absence of muscular regulatory oversight. In a burgeoning industry, the number of inspections and compliance reviews needed to assess an operator’s safety performance had overwhelmed the modest resources of regulators. Moreover, it was easy for bus operators to launch new businesses and to escape requirements that they submit basic data, such as mileage information, to federal regulators.

Over the past five years, the government has doubled the number of bus inspections. It has also banned texting or any other use of mobile phones by commercial drivers. That’s a good start; so is a mobile app called SaferBus that enables passengers to review a bus company’s safety record before buying a ticket.

Other measures are hung up in a broad transportation bill before Congress. Those include requiring new bus operators to submit to a full safety audit before they can start carrying passengers; increasing the fines (now just $2,200 a day) for carriers that operate without proper authority; and expanding regulators’ power to go after bus operators that are ordered closed, only to re-create themselves under a different name.

It’s important that passengers who have come to rely on curbside operators for their prices and ease of service continue to have confidence that they are in safe hands when they board the bus. The federal investigation is a strong step in that direction — but it’s just a first step.