Passengers crowd the sidewalk at the Megabus stop at West 33rd Street and Ninth Avenue on Dec. 20, 2011. View Full Caption DNAinfo/Mathew Katz

MANHATTAN — Megabus' double-decker coaches, currently being investigated by New York's Department of Transportation, have run afoul of authorities from Canada to Maryland, DNAinfo has learned.

As the city's DOT delves into complaints that the vehicles are too heavy for city streets, officials in Maryland and in Quebec are looking at whether or not they're safe to be on their roads.

In September, the Quebec Transportation Commission shot down the company's request for a permit to operate a double-decker route between New York and Montreal in two-story Van Hool TD925 buses that allow the discount carrier to pack in 81 passengers — twice the number that fit on a regular bus.

The commission cited a document from the coach's manufacturer stating that a coach at full capacity weighs 40,106 pounds — far more than Quebec's limit of 27,500 pounds.

"In order to make reduced fares feasible, the carrier asked to use only coaches with double floors (better known as called "double-deckers") allowing it to carry ... 81 people at a time," the commission wrote in its decision. "By analyzing more closely these elements of the application, the Commission realized that the buses … did not meet the standards of Quebec."

A measurement taken by the New York State Police for Adirondack Transit Lines, a Megabus competitor, also found the buses weigh about 40,000 pounds when full — 4,000 pounds heavier than the New York state's legal limit.

Megabus attorney Cecelia Fanelli argued in a legal brief that the Quebec decision is irrelevant in New York City, because New York's limit is much higher than Quebec's.

But Quebec is not alone in raising questions about the dangers of the overweight buses. In 2010, four passengers were killed when the top of a double-decker Megabus crashed into an overpass outside of Syracuse. The driver of that bus was acquitted of manslaughter in court Tuesday.

And in a March 2010 incident, a Maryland State Police officer pulled over a double-decker Megabus outside of Baltimore, fearing for the safety of passengers.

The officer took the bus to a weigh station, where it was found to be overweight, police said.

Customers were forced to wait for hours at a mall in Perryville, Maryland, until another, single-decker bus arrived to complete the journey from New York to Washington, D.C.

"The bus weighed 3,800 pounds over the limit," Terry Katz, Program Manager for Maryland's Commercial Vehicle Enforcement, told DNAinfo.

"The reason weight is a big issue for those things is the damage to the road it can cause."

Despite the excess weight, Katz said, he still believes Megabus coaches are far safer than other, single-decker coaches run by less reputable companies.

"Megabus is one of those companies that has good maintenance records," he said. "They're far better than an average bus company."

Megabus did not responded to requests for comment for this story.

A spokesman for the DOT would not comment on the investigation.

Van Hool, a Belgian company, largely builds coaches for European carriers and only recently began to sell to North American companies.

Megabus recently moved many of its Manhattan pick-ups to a stop on West 41st Street, between Eighth and Ninth Avenues, which is sandwiched between two sections of the Port Authority Bus Terminal.

The carrier's competitors have sued the city, arguing that they pay millions of dollars to operate out of the terminal, and that the free stop for Megabus creates a non-competitive environment.