Mind the Overlap: Toronto Transit Commission Maps Conflicts Before They Happen

The Toronto Transit Commission (TTC) is Canada’s largest public transit system, connecting communities across Toronto for more than 100 years. With a comprehensive network of bus, paratransit, streetcar, and subway services that span the city’s 630 square kilometers, the TTC is critical infrastructure. It made more than 396 million customer trips in 2023.

Effective coordination of construction activities in complex operational environments is critical to minimizing risk, avoiding delays, and maintaining service continuity. To address this challenge, TTC developed the Project Interface Manager (PIM) solution. PIM includes a geographic information system (GIS)-based web application designed to identify and manage spatial and temporal conflicts between planned construction projects. By integrating geospatial data, scheduling information, and automated analytics, PIM transforms traditionally fragmented project coordination processes into a centralized, data-driven workflow that supports proactive decision-making.

Greenwood Yard is the TTC’s primary facility for maintaining and housing all Line 2 subway trains. Multiple business expansions are underway within the yard, and  each expansion adhering to distinct mandates: maintaining assets in a state of good repair, delivering new infrastructure to support system expansion, and ensuring uninterrupted transit operations despite increasing service demands.

Historically, coordination between these groups relied on manual processes that included disconnected schedules, siloed communication, and inconsistent data sources. This approach led to duplicated efforts, rework, and overlapping work areas that increased the risk of operational disruption. As capital programs expanded, a more systematic, program-level approach was needed to manage project interfaces, dependencies, and conflicts efficiently and transparently.

To support this shift, PIM leverages ArcGIS Online as a foundation for integrating spatial and nonspatial data into a unified system, enabling consistent data hosting, sharing, and analysis across projects. Key components include:

·         ArcGIS Experience Builder for application configuration and user interface design

·         ArcGIS Notebooks (Python) for automated conflict-detection workflows

·         Custom JavaScript components for advanced visualizations in Gantt chart integration

·         Digitized CAD/PDF drawings transformed into authoritative GIS datasets

In developing PIM, TTC worked with Esri partner GFT to establish a structured pre-implementation phase focused on consolidating schedules and defining spatial frameworks. Project schedules from multiple business units were standardized and compiled into a common comma-separated variable (CSV) format, then integrated into a centralized environment using ArcGIS Online for data hosting and sharing.

A critical component of this phase was the development of Workzones, a spatial framework that is used to represent project locations and enable conflict detection. For Greenwood Yard, the locations in Workzones were intentionally specific level, such as North Track 31, South Track 31, and the Painting and Sanding Booth, to balance clarity and usability for a broad audience while still supporting meaningful spatial analysis.

The creation of these Workzones data layers required digitizing as-built floor plans from computer-aided design (CAD) drawings and stitching together historical records to construct a comprehensive GIS representation of the rail yard, including tracks, signals, buildings, and internal rooms. This structured spatial foundation, combined with ArcGIS Notebooks, enables the automated generation of project locations and space-time conflict detection.
 

To support schedule visualization, the TTC and GTF team developed a custom Gantt chart widget using the DHTMLX JavaScript UI library, providing a familiar and intuitive way to understand project timelines and overlaps. The PIM application was built using customizable tools in ArcGIS Experience Builder and deployed via Azure Web Apps, ensuring flexibility and scalability.

Together, these technologies enable real-time visualization, automated analysis, and scalable data management within a single, accessible web-based environment. These capabilities are delivered through a set of application modules designed to support project coordination at different levels.
 

The Viewer module serves as the central interface of the PIM application, providing an interactive, map-based view of all planned construction projects. Users can explore project extents, schedules, and associated attributes in a single environment, helping TTC teams understand how projects interact spatially across the yard. By consolidating data sources into a unified visual interface, the Viewer module improves situational awareness and supports more informed coordination between teams.
 

For more focused analysis, the Single Project Verifier module enables users to evaluate individual projects in detail against all other planned projects within the system. Using spatial and temporal analysis, the tool identifies potential conflicts such as overlapping work zones, schedule clashes, or access constraints. This helps project teams validate and refine their plans before execution, reducing conflicts and minimizing reactive adjustments.
 

To support broader coordination across programs, PIM extends this capability to multiple projects simultaneously with the Multi-Project Verifier module. Designed for program-level coordination, it helps TTC staff identify cumulative conflicts across a portfolio of projects.

The implementation of PIM has improved coordination and efficiency within Greenwood Yard. By identifying dependencies early, PIM reduces duplicated efforts and minimizes costly rework. The centralized environment improves cross-departmental visibility, breaking down silos and enabling more effective collaboration between stakeholders. Integrating spatial and schedule data also provides clear, visual insights that support proactive, data-driven decisions, allowing teams to resolve conflicts before they impact operations.

PIM’s outcomes also highlighted several key lessons for implementing GIS-driven project coordination at scale. Early and ongoing stakeholder engagement ensures that the solution aligns with real-world operational workflows and user needs. Data standardization and governance remain critical for consistency and reliability across multiple project inputs. Balancing custom functionality with existing capabilities helps support long-term maintainability and scalability. Finally, investing in knowledge transfer and staff training strengthens adoption and ensures that the system continues to deliver value over time.

Building on this foundation, future enhancements to PIM focus on increasing automation, improving spatial context, and expanding collaboration capabilities. Integration with the P6 microarchitecture is being considered to further automate schedule updates, reducing manual input and minimizing the risk of human error. Incorporating 3D visualizations will provide deeper spatial understanding of how facilities and assets interact within concurrent projects at the yard or across TTC’s network.

Also, ArcGIS Hub presents a future opportunity to support collaboration with external design teams by enabling the submission of materials such as construction staging plans or laydown areas. These inputs can then be reviewed, processed, and integrated into TTC’s GIS environment, creating a consistent and centralized data repository. In turn, this supports more coordinated and conflict-free project execution.