Metrolinx: Mainstreaming Climate Risk Assessment

Metrolinx, a public transportation authority in Ontario, realized that creating an adaptation strategy could help it manage climate change risks across the Greater Golden Horseshoe region. Using climate information to inform services, operations, maintenance, and infrastructure, Metrolinx is helping to prevent climate impacts ranging from transit delays to premature infrastructure failures.

Writing Credits: Leigh Phillips. Contributing Authors: Elaine Barrow, Nathalie Bleau, Jessie Booker, Taylor Livingston, Lindsay Matthews, Stacey O'Sullivan, Amanda Patt, Kari Tyler.


The implementation of the PIEVC Protocol across Metrolinx, Canada’s largest transit authority, identified key climate risks such as extreme heat impacts on rail lines and risks from ice on roadways and passenger platforms as freeze-thaw cycles persist. The assessment supported the development of an organization-wide adaptation strategy and a commitment to the ongoing understanding of climate change impacts of specific interest to the organization.


Metrolinx is the Ontario government agency responsible for public transport across the Greater Golden Horseshoe (GGH) region. It is one of the largest crown corporations in the country, running the GO Transit commuter rail and bus system, the Union Pearson Express airport rail link, and the Presto card fare system for 11 different municipalities (including Ottawa), as well as overseeing subway development and other rapid transit projects in Toronto and the GGH.

In 2013, the agency suffered two climate-related disasters back-to-back: a flooded train in July in addition to two washouts along the tracks, and an ice storm in December in which some stations went without power for a week. Metrolinx decided it was time to take climate adaptation seriously. They brought in climate risk expert Quentin Chiotti, creating a new senior advisor position dedicated solely to the question of climate risk and adaptation.

Climate Risk Assessment

To understand where they might be vulnerable, Chiotti and a “dream team,” as he describes them, of risk science experts applied the PIEVC Protocol to six of the agency’s assets that were representative of Metrolinx as a whole. They chose a representative selection of infrastructure (two each of stations, facilities, and segments of rail corridors) to assess with the PIEVC Protocol. While the report from this assessment is not publicly available, the process and findings are described within the 2017 Planning for Resiliency: Toward a Corporate Climate Adaptation Plan document, which informed the organization-wide Climate Adaptation Strategy.

The assessment of risk caused by an increasing frequency of hot days has led Metrolinx to change the temperature threshold at which they lay new rail track, and re-assess the number of days that are likely to face “slow-go” orders.

Another risk identified by the assessment is the persistent frequency of freeze-thaw cycles (days when the air temperature fluctuates between freezing and non-freezing temperatures). The freezing, melting, and re-freezing of water can damage infrastructure and have negative impacts on vehicle and passenger safety.

Climate Impact: Extreme Heat

As shown in Figure 1 below, the hottest day in the past was in the low 30°Cs (on average). The projections for the decades surrounding the 2020s indicate that the average hottest day has likely already increased to the mid 30°Cs and that in the decades around the 2050s (in medium and higher emissions scenarios) it could approach 40°C. This has implications for rail corridors as the radiant temperature of steel tracks will be much higher than ambient air temperatures.

When continuous welded rail tracks are installed in a corridor, they first have to be stressed according to a regionally-appropriate rail laying temperature. Across Canada, this temperature has traditionally been 32.2°C. The climate-induced increase in the average summertime daily temperature has prompted Metrolinx to adopt a higher temperature for rail laying, of 37.7°C for all new track. Metrolinx assessed this Preferred Rail Laying Temperature (PRLT) by comparing it to future maximum temperatures from portal projections. The PRLT of 37.7°C should be sufficient to allow operations to run safely within future maximum temperatures, at least for the next decade or so. Until then, track and ambient air temperatures are being monitored, and the PRLT periodically reviewed as maximum temperatures rise.

Sustained air temperatures above 30°C can also cause what are called “sun kinks” in steel rails. This poses a safety issue if trains pass over them too quickly. Slow-go orders are typically imposed when temperatures exceed 30°C. Train speeds are cut by 24 km/h, which can add about 10 minutes to the average trip. As these hot temperatures are occurring more often, there will be an increased number of “slow-go orders” and corresponding travel delays.

Figure 1. Changes to the Hottest Day over the 21st Century for Toronto, ON

Changes to the highest maximum temperature in a given time period, simulated over the 21st century by an ensemble of global climate models. Different colours refer to different future emissions pathways (RCPs), with heavy lines showing the multi-model median and lighter shading indicating the multi-model range. Hover your mouse over 30-year periods on the figure to assess projected average changes to the hottest day in Toronto over time, under three emissions scenarios. 

Climate Impact: Freeze-Thaw Cycles

Freeze-thaw cycles, in which snow melts and then re-freezes as ice, can lead to bus collisions and slips and falls on outdoor platforms, stations, sidewalks, and parking lots. As winters warm, freeze-thaw cycles in Toronto may decrease in frequency over the long-term and under higher emissions scenarios, but are projected to persist at a similar frequency to historical conditions under low (RCP2.6) and intermediate (RCP4.5) emissions scenarios (Figure 2). There are a number of tools available to address this problem, including snow removal, salting, and infrastructure that melts snow on contact. This has knock-on considerations for transit stations: should Metrolinx install heating systems to melt snow on platforms, or continue to rely on snow clearing and salt management? The former is not cheap, and would have a negative impact by increasing greenhouse gas emissions, as they have traditionally used natural gas boilers. How does this compare to improved salting of platforms? Metrolinx utilizes both strategies depending on a variety of factors and local context, including energy efficiency. They are investigating energy options (e.g., natural gas vs electricity) for platform snow melting systems, and the use of improved weather forecasting to inform snow clearing and salt management practices. How these options are impacted by climate change in the intermediate (10 year) and long-term (asset lifecycle) is also an important consideration.

These decisions, and many other policy, planning, and strategic questions were brought to the fore by the climate risk assessment process. This is part of the value of applying the PIEVC Protocol, through which historical climate data, future climate projections, and multi-disciplinary stakeholder input is evaluated to identify climate risks and make informed adaptation decisions.

Figure 2. Changes to Daily Freeze-Thaw Cycles over the 21st Century for Toronto, ON

Annual number of daily freeze-thaw cycles simulated over the 21st century by an ensemble of global climate models. Different colours refer to different future emissions pathways (RCPs), with heavy lines showing the multi-model median and lighter shading indicating the multi-model range. Hover your mouse over 30-year periods on the figure to view projected average changes to freeze-thaw cycles in Toronto over time, under three emissions scenarios. 

Risk Assessment Conclusion

The assessment found that climate risks pose a threat to on-time performance, customer complaints and reputation, working conditions, and health and safety. While these risks may not result in infrastructure failure, they still create a profound threat to the organization over time. Passengers get frustrated with such annoyances or modest dangers when compared to what they imagine efficient, well-run transit should look like.

“You’ll notice that a lot of these aren’t exactly what you’d call catastrophic risk,” says Quentin. He thinks there has been too much of a focus on catastrophic risk in the adaptation sector. “These are real concerns, but organizations like Metrolinx also need to ask themselves: ‘How does this impact our day-to-day operations?’ It’s not just about floods and ice storms.” While addressing the catastrophic risks from extreme weather conditions is important, so too is being able to deliver reliable and safe transit service under a wide range of weather conditions.

Teasing out these interlocking relationships is complex work. For example, a number of snow-related contracts are tied to a set start of the winter season, but both the season start and end dates are changing now. It sounds banal, but there are hundreds of such issues. Quentin says he’s lucky that there is buy-in for taking climate vulnerability seriously across the organization, especially at the executive level, and that Metrolinx has staff committed to the task of assessing climate risks and considering them in operations, asset management, and the design and construction of new infrastructure. “Climate risk now has a direct sightline to senior management, which keeps it fresh and on people’s radar. The next few years for this stuff will be absolutely crucial.”

Key Takeaways

  • Existing and future transit infrastructure need to be designed and built with consideration for the fact that the climate has already changed and that those changes will continue into the future.
  • Decision making processes, policies, and strategic planning also need to account for current and future climate risk.
  • Some aspects of infrastructure will be at risk, not just to extreme events, but to impacts of changing average conditions.


The authors would like to express their sincere gratitude to Quentin Chiotti and the team at Metrolinx for their invaluable contributions to this case study.