In March, a Chinatown bound bus returning from a casino careened off the road and was shorn in half, killing 15 people. Two days later, a driver and a passenger perished when a bus traveling from New York to Philadelphia hurtled into an embankment off the side of the New Jersey Turnpike. And on Tuesday, a bus owned by Sky Express rolled over in Virginia, killing four people.

The spate of deadly interstate bus accidents has renewed scrutiny of the bus lines that ferry customers between East Coast cities for a small fee, with elected officials and advocacy organizations calling for increased regulation and stepped up inspections. The Department of Transportation has already responded to the revelation that the Sky Express accident occurred while the company was appealing a suspension by moving to eliminate such appeals. A Senate subcommittee was convened to examine the issue. Sen. Chuck Schumer (D-NY) and Rep. Nydia Velazquez (D-NY) have called for an investigation and a bipartisan bus safety bill is advancing.

I think the problem, when you look at how the accidents happen, is very simple, said Peter Pantuso, president of the American Bus Association. It's rogue operators who operate outside of the margins of safety and are allowed to be on the road.

Pantuso pointed out that many bus lines operate even when inspections uncover violations, an assertion supported by a WNYC investigation that found a third of intercity bus companies in New York State had been issued safety warnings. The three deadly crashes all followed recorded violations: the bus driver in Virginia had been cited multiple times for driver fatigue; the driver of the bus returning from the casino had been arrested for driving with a suspended license; and a compliance review of Sky Express had led the Motor Carrier Safety Administration to bar the company from interstate travel after finding poorly maintained vehicles and insufficiently trained drivers.

But inspectors lack both the resources and the manpower to properly enforce regulations, Pantuso said. Inspection policies also vary from state to state, which Pantuso said gives companies who register their businesses in more lenient states a free pass.

At the end of the day it's the government that is to maintain that responsibility and that credibility, in the same way that the Federal Aviation Administration ensures that when you step on the plane at the airport you're traveling on a safe plane, Pantuso said. Consumers need to be aware of who they're traveling with and riding with.

Lawmakers in New York State are pushing legislation that would enhance their oversight of buses that pass through New York City. State Senator Daniel Squadron has repeatedly decried the Wild West atmosphere of Chinatown, a neighborhood encompassed by his district that has long been a hub for the inexpensive Chinatown buses that shuttle between the Chinatowns dotting East Coast cities. Squadron's legislation would require that every bus picking up or dropping off in New York City obtains a permit from the city (a version of the bill has already passed New York's Assembly).

We would have a sense of who is operating, Squadron said, noting that he did not know the number of bus companies that pass through New York City. We would be able to cross-reference that with the federal data and do a better job of identifying problem actors before tragedies occur.

Squadron added that the problem lies with fly by night operators, and that the rapid growth enjoyed by inexpensive intercity bus companies in the last decade has advantages. Joe Schwieterman, a professor of transportation at DePaul University who directs the Chaddick Insitute for Metropolitan Development, said that buses are safer and more environmentally friendly than cars and cautioned against overly restrictive legislation in response to the bad apples giving the industry a bad name.

The problem seems to be primarily in the quality of the drivers for several less reputable companies working really long shifts or being inadequately trained, Schwieterman said. It doesn't seem to be as much a problem with the bus technology itself.

The intercity bus industry has grown at a remarkable rate in recent years, due largely to the success of carriers like Megabus and Bolt Bus that have attracted riders beyond the demographic of young people trying to save money, Schwieterman said. These mainsteam carriers are beginning to edge out the Chinatown buses that, along with Greyhound, traditionally dominated the market.

I interpret that as the Chinatown buses being replaced by more mainstream carriers, which I interpret as a positive development for safety, Schwieterman.