A week after a deadly bus explosion in northeast Calgary, the area councillor is calling for an independent investigation into the crash.
The collision Oct. 15 involving two city transit buses and several other vehicles in Saddle Ridge led to an explosion on a natural gas powered bus, resulting in three deaths and 16 injuries.
Both the Calgary Fire Department and Calgary Police Service told CBC News an investigation into the cause of the fire is in the early stages, with Transport Canada saying it is also assisting.
Coun. Raj Dhaliwal has called the crash a “freak accident,” and told reporters on Thursday he wants to see an independent investigation outside of the fire and police probes.
“If it’s one person, two person — I don’t care as long as it’s done externally and there’s no biases built into final recommendations,” he said.
Ward 5 Coun. Raj Dhaliwal, who represents the community where the crash occurred, says he would like to see an independent investigation consider transit-specific and road design factors. (Brendan Coulter/CBC)
Dhaliwal added he would like to see a comprehensive review similar to that conducted following two ruptures of the Bearspaw feeder main, taking into consideration both transit-specific factors and the design of the intersection where the collision occurred.
“It’s surety to [transit users] that, hey, we did look at it,” Dhaliwal said. “We went to the bottom of it. We did the root cause analysis and we can assure you, whatever the results we will be, if there’s any recommendation, we want to implement those.”
Some people have raised concerns over whether Calgary Transit’s compressed natural gas (CNG) buses, which make up roughly 30 per cent of the city’s bus fleet, remain safe for operation.
But two experts say incidents like this one are rare, and while CNG buses differ from diesel-powered ones, they do not pose a significantly higher risk, and adhere to strict testing and maintenance guidelines to ensure their safety.
CNG vs. diesel
“The designs are such in the regulations and the design standards that this should not have happened,” said Gordon McTaggart-Cowen, a professor in Simon Fraser University’s School of Sustainable Energy Engineering.
He explained that CNG engines are designed to withstand fire, and go through frequent testing to ensure they remain safe.
Video recorded at the scene of a fiery bus crash and explosion shows a bystander rushing to rescue someone from the flames.
“The tanks go through bonfire tests to determine that they can withstand being placed in a fire, and that either they can withstand the fire, or that they can release the gas fast enough that they don’t rupture,” he said.
CNG engines differ from diesel engines in that they require a spark plug to start, he said. Whereas a diesel engine compresses air to ignite, CNG acts more like gasoline in that it requires some type of spark to ignite the fuel and run.
“Natural gas is inherently relatively difficult to burn,” McTaggart-Cowen said. “You’d have to have a fairly high temperature or a reasonable sized spark to get it to ignite under the right conditions.”
According to Natural Resources Canada’s website, natural gas is “just as safe as gasoline” when handled properly, and requires a higher concentration of the gas and a hotter ignition source to combust.
“Because natural gas is stored under pressure, natural gas fuel systems are robust and hold up well in accidents,” the website said. “This has proven to be a safety advantage over gasoline vehicles.”
Calgary police are sharing more details on the deadly bus crash and explosion in Saddle Ridge that left three people dead on Thursday, but say it’s too early to determine the cause. The transit union says both bus drivers and the public need to know what happened quickly, so they have peace of mind when travelling on the city’s fleet.
The engines are also equipped with pressure-release valves, McTaggart-Cowen said, which are designed to automatically release the gas should the engine ignite. Tanks are also designed to withstand fire for approximately 20 minutes.
While he did not want to speculate on the cause of the Calgary crash, he said the collision between the two buses could have ruptured the CNG fuel line, potentially leading to the fire.
CNG not a new technology, expert says
There are close to 1,000 CNG buses on Canadian roads, said Josipa Petrunic, CEO of the Canadian Urban Transit Research and Innovation Consortium.
Calgary has been phasing in natural gas powered buses since 2014, while transit agencies in other Canadian cities like Hamilton and Vancouver have also been increasing their use of the buses in recent years.
“Compressed natural gas buses today in Canada are not considered new technology. They are considered established commercial technology,” she said. “These vehicles are generally considered very safe for operation in Canada and that’s why they operate on roads.”
The buses are often chosen for two reasons, Petrunic explained: natural gas is both cheaper and cleaner burning than diesel.
But unlike diesel, the fuel in CNG tanks has to be kept at a high pressure, she said, meaning the tanks are also the “heaviest, sturdiest” part of the vehicle.
“The tanks are really heavily engineered to prevent any kind of cataclysmic event from arising because of a pressure failure or an explosion,” she said.
This also means the buses are subject to intensive testing protocols, with one of the most common being Altoona testing at a lab in Pennsylvania, Petrunic said. Altoona testing evaluates vehicles for mechanical or electrical failures, Petrunic said, as well as fuel leakage.
“Canadian buses are actually often criticized or questioned just in terms of how over-engineered they are, whether it’s diesel or compressed natural gas or battery electric or hydrogen,” she said.
Calgary Transit has previously told CBC News it is working with investigators, and will assess its CNG operations to understand if more safety measures are required.
Despite the existing “rigorous” regulations, opening a dialogue around safety measures and potential improvements remains important, Petrunic said.
“If anything can come out of this, then hopefully it would be safer standards in the future, if that is in fact what the gap was,” she said.
