A car attack at a Filipino street festival in Vancouver just two days before Canada's federal election has killed at least 11 people and injured many more.

The carnage along a street lined with food trucks took place shortly after one of the men vying to become Canada's prime minister - New Democratic Party Leader Jagmeet Singh - attended the event. A shell-shocked Singh observed a moment of silence in Penticton, B.C., during another campaign stop the next day.

A 30-year-old Vancouver resident has been arrested, but the motivation behind the attack is unknown.

Vancouver police say the suspect has mental health issues and was known to police prior to the attack. Police also told a news conference there was no indication there was a need for extra policing at the festival, deeming it to have a "low threat level."

What goes into making that calculation, and is a public event ever truly low-risk?

The Vancouver SUV attack is now classified as a crowd-related or mass gathering type of disaster. There have been cases of public vehicle-ramming attacks in Canada in the past, in particular the 2018 Toronto van attack that left 10 people dead.

While it's not yet known whether the Vancouver attack was targeted, there were clearly weaknesses in crowd management for such a large gathering. These types of attacks have been on the increase over the past decade and are now considered one of the prime threats to mass gatherings in public spaces and streets.

Unfortunately, many mass gathering events do not allocate either sufficient resources or time for crowd management procedures, particularly those related to risk and emergency management.

Organizing mass gathering events in public spaces should factor in different threats, including the potential for car ramming, and implement effective mitigation and preparedness measures.

Many public spaces where these events take place are vulnerable to car attacks. Evidence shows that mass gatherings are soft targets, meaning they're easily accessible to large numbers of people and have limited security, protective and warning measures in place. Extreme precautions are needed to protect the public from such attacks so that they don't become mass casualty events.

Those in attendance should be aware that public spaces generally lack physical barriers, or the proper distribution of them, to resist car or vehicle attacks.

While public awareness programs exist for other hazards such as flooding, earthquakes and extreme weather events, it's now clear that such awareness and education are needed for mass public gatherings too.

Police should be aware that relying on limited surveillance may not be sufficient to identify such threats at the scene. Vehicle access and traffic control should be in place throughout such events. Lack of warning systems to quickly inform the crowd about an ongoing attack further increases the impacts of vehicular attacks.

Much of the focus on these types of events has been on the motivations of the attackers. Since a considerable number of vehicle-ramming attacks have been attributed to terrorism, communities or events with the perception of lower terrorism threats may not pay close enough attention to this type of threat.

Read more: Toronto's most recent car attack was a targeted crime, not a mass attack

Canadians aren't likely to get many more details about the Vancouver attack until after voting day on Monday. Could the tragedy have an impact on the outcome of the federal election?

Past and recent studies have drawn different conclusions about the impact of disasters on election results.

According to what's known as retrospective voting theory, voters judge governments on how they manage disasters, particularly highly publicized, tragic events, when casting their ballots. Voters can evaluate governments based on their handling of the disaster and the amount of effort they have put into minimizing risk.

Some studies have found that local governments were rewarded after disaster events, including Calgary after the 2013 floods, several Italian municipal governments after earthquakes, local government officials in Brazil amid municipal drought declarations and civic elections in Japan after earthquakes, tsunamis and floods.

Read more: Why Canada needs to dramatically update how it prepares for and manages emergencies

Voters can and do punish or reward governments and elected politicians based on the effects of recent disasters on them and governments' responses to them.

But given how soon the Canadian election is being held after the disaster occurred - and the record number of voters who have already cast their ballots in advance polls - this tragedy isn't likely to have a substantial impact.

Hopefully, however, it will have an influence on how organizers, police and other authorities manage public crowds and events at a time when vehicle-ramming attacks are becoming a recurrent threat. Those elected this election should prioritize efforts to ensure communities can have safer mass gathering events.