Canada is the only G7 country without a high-speed rail line, yet not for lack of trying. Over the last half century, numerous high-speed rail projects have been proposed, studied and even approved by political leaders. The obstacles to actually getting them built have proven insurmountable thus far. Proponents of high-speed rail had much to celebrate earlier this month when Prime Minister Justin Trudeau announced Alto, a high-speed train line that will connect Québec City and Toronto, with stops in Trois-Rivières, Laval, Montréal, Ottawa and Peterborough. After a lengthy tender process, the $3.9 billion six-year contract was awarded to the Cadence consortium, which comprises Air Canada, CDPQ Infra, AtkinsRéalis, Keolis, SYSTRA and SNCF Voyageurs. The consortium will work with the federal government to bring the proposed high-speed rail line to fruition. Yet, while this announcement is a milestone, multiple political and economic hurdles must be cleared for this project to ever see the light of day. Politically uncertain futureFour main challenges stand between Trudeau’s announcement and the first high-speed journey. The first is the current political context. With an election on the horizon, the project’s fate could hinge on which party forms the next government.Trudeau announced the project less than a month before the pre-determined end to his tenure as prime minister, and it remains unclear who will be Canada’s next, how long their term will last or which party (or coalition) will form the next government. Conservative Party leader Pierre Poilievre currently leads the polls, and although his party has expressed support for high-speed rail infrastructure, it also has called for a major scaling back of government spending.History could very well repeat itself if Poilievre comes to power and cancels the project — just as Ontario Premier Doug Ford paused funding and halted plans for the high-speed rail project his Liberal predecessor, Kathleen Wynne, had announced upon taking office.The federal Conservatives have already criticized the recent high-speed rail announcement. In contrast, Mark Carney, who is currently the frontrunner for the Liberal Party’s leadership, has expressed support for high-speed rail, but he has also made comments about the need to reduce spending.The cost factorBeyond political risk, the second major challenge is cost. Canadian governments have, on multiple occasions, engaged in commercial feasibility studies of high-speed rail projects, only to abandon plans once a clearer sense of the price tag emerged.The recent announcement involves a $3.9 billion federal commitment — but this funding is only for the next design phase of the project. This phase includes route planning, station location identification, environmental assessments and consultation with Indigenous communities.At the end of this multi-year phase, there should be a plan in place, but there will still not be any actual material infrastructure built or rail equipment purchased. The actual costs of construction and physical asset procurement remain uncertain, with estimates ranging from $80 to $120 billion. Considering the cost of other high-speed rail projects around the world, a 1,000 kilometre high-speed rail line would likely cost tens of billions of dollars.Regional politics and fairnessThe third obstacle lies in inter-provincial and regional politics. Large-scale infrastructure projects in Canada have faced resistance from provinces that feel excluded, and this high-speed rail initiative is no exception.One study on the political economy of Canadian high-speed rail identified inter-provincial and regional politics as a central challenge for a costly Québec-Ontario project such as this one. Ottawa risks being accused of funnelling billions of taxpayer dollars into a massive infrastructure project that only directly benefits two of Canada’s provinces. This could create friction with the Western provinces, the Prairies, the Maritime provinces and the Northern territories, whose leaders and residents may ask what they might get in return.An additional challenge is the perception that the project is a Trudeau-era legacy initiative. Some may see the investment as another example of “Laurentian elites” disproportionately benefiting from the nation’s resource wealth — a long-standing narrative used to critique inter-provincial economic disparities.Time and executionFinally — though not exhaustively — time itself could prove to be a hurdle. The current co-development phase of the project is expected to last up to five years, after which additional funds and decisions will be required before the build phase can begin. Even if the project goes ahead, large-scale infrastructure projects are notoriously prone to delays and cost overruns. There is a well-known saying in megaproject development: projects like this tend to be “over budget, over time, over and over again.”This raises concerns that Alto could face serious delays or even failure, as the proposed plan needs to sustain not only the next five years of inter-provincial and federal politics, but also the subsequent build phase.A cautionary example is California’s high-speed rail line, which originally intended to link San Francisco and Los Angeles by 2020 at a cost of US$33 billion. Today, only a portion of the infrastructure has been built, cost estimates now exceed US$128 billion, neither major city is yet connected and there is no clear completion date in sight.Possibility of transformationThe Alto project marks a significant step toward Canada joining the ranks of nations with high-speed rail. However, political and economic realities serve as a reminder that many obstacles have yet to be overcome before that vision becomes reality. If done right, this project could usher in a new era of 21st-century sustainable transport infrastructure in Canada. If done wrong, the project will rack up costs, sow political division and waste taxpayers’ dollars. How domestic political economic realities evolve in the coming months and year will have a significant bearing on whether this is the high-speed rail plan that finally breaks through.Ryan M. Katz-Rosene does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.