Sound Transit 3 (ST3), the most ambitious transit expansion effort in the region’s history, is encountering a significant cost crisis. Project budgets have soared beyond the initial estimates, posing the risk of derailing the entire program. With the federal funding landscape increasingly uncertain, Sound Transit is compelled to discover dramatic cost reductions to avoid unfulfilled transit line promises.
Among the various components contributing to transit construction expenses, stations carry the most weight. Elevated stations generally double the cost of surface stations, while underground stations can quadruple those costs. Therefore, cutting expenses associated with underground stations is pivotal to managing overall project budgets.
In 2024, New York University’s Transit Cost Project published a case study that sought to determine why the first phase of New York City’s Second Avenue Subway extension, completed in 2017, ended up costing significantly more than comparable projects in Europe. The findings revealed that the newer stations were nearly twice as long as those in European projects and even longer than previous designs from the 1970s for the same project. Most notably, the study highlighted that subway stations in France, Sweden, and Italy typically maintain dimensions barely exceeding the length of the trains they serve; anything beyond a 5% excess is considered typical, while 20% is considered excessive.
Informed by these insights, Nolan Hicks from NYU’s Marron Institute reported a similar issue in the design of the next expansion phase. In response, the Metropolitan Transportation Authority (MTA) revised its second phase of the Second Avenue Subway design, resulting in over $300 million in savings through smaller station dimensions.
With the Transit Cost Project’s findings in mind, this article will evaluate all of Sound Transit’s underground light rail stations, both those constructed and those planned under ST3. Earlier phases, notably the Downtown Seattle Transit Tunnel (DSTT) through Sound Transit 2 (ST2), already exhibited tendencies toward overbuilding and overdesign, with these issues magnifying in ST3. There is an enormous opportunity to save hundreds of millions by following the MTA’s example to optimize station designs.
This entails a fundamental rethinking of how Sound Transit develops its station architecture and lobbying for supportive state legislation.
The trend of increasing station dimensions has persisted through each expansion phase—from the repurposed DSTT in Central Link to ST3. Stations have become progressively longer relative to the required platform area.
For instance, Sound Move stations (from the DSTT) were 50% longer and 50 to 60 feet deep.
ST2 stations averaged 43% longer and were around 75 feet deep.
By ST3, stations are now 79% longer and average a depth of 108 feet.
In comparison to these figures, the newly standard underground station design (cut-and-cover) is 45% longer and extends 90 feet deep. These station lengths vastly exceed the maximum 20% threshold noted in European stations.
The implications of increased size on cost escalate dramatically, particularly as mined construction is being proposed for Midtown and Westlake Center. The NYU Transit Cost Project discovered that mined stations cost 1.5 times more per volume than cut-and-cover alternatives seen in the 2nd Avenue extension project.
Note: All station lengths referenced stem from Environmental Impact Statement documentation which was utilized for consistency and accessibility of information—final design lengths and profiles may differ from those presented herein.
Exploration of Sound Transit 3 Underground Stations
Sound Transit’s existing and proposed stations significantly surpass the size of stations completed or currently under construction in European cities such as Paris, Milan, and Rome. The Paris Metro Line 14 extension, inaugurated in June 2024, reveals strikingly compact designs with minimal excess excavation beyond platform dimensions while optimizing the use of excavated space for vertical movement. The design of most station access occurs within the station structure.
Photos presented illustrate the longitudinal and cross-sectional views of Paris’ Line 14 stations.
Rome’s Fori Imperiali Station construction also exemplifies efficient station design within challenging contexts, as it is being built on an active archaeological site. Ingeniously, artifacts uncovered during construction are being used to establish a ‘museum station’ experience. The difficulties faced by Italian engineers in preserving the integrity of a 2,000-year-old archaeological site greatly parallel the challenges found in Seattle, yet the resultant station remains shallower, smaller, and more efficient than Sound Transit’s proposed stations in comparably simple environments.
The American context stands in stark contrast; after a period of rail transit stagnation following the 1960s, many systems encountered years of neglect, epitomized by the financial crises of institutions like New York’s MTA. In contrast to European and Asian countries that continued to innovate and build rail systems, American transit has been marked by triage and stabilization.
Sound Transit and other U.S. transit agencies frequently fall prey to a pattern of overbuilding and overdesign driven by several factors: design inertia, excessive interpretation of design codes, and stakeholder-influenced design decisions.
Response to Design Inertia
In the U.S., the New York Metro remains the primary national reference for underground construction. Among various design elements, Sound Transit has adopted oversized full-length mezzanines from the New York model. While those are practical for accommodating large passenger volumes and transfers, they may not be necessary for Link’s needs based on contemporary design practices. New York itself has recognized certain shortcomings in station sizes but continues to iterate on designs with lingering issues.
This inertia is evident in Sound Transit’s standard configuration for underground stations, which is now 45% longer than the platform itself. Expert feedback collected through the Technical Advisory Group (TAG) led to the creation of this standard. Despite an intent to promote optimal designs, the resulting oversized design proposal showcases an institutional preference for large stations.
Stations on Milan’s Lines 4 and 5 provide an effective contrast to Sound Transit’s approach, showcasing efficient use of vertical space to minimize excavation needs while enhancing user experiences.
Overinterpretation of Regulatory Codes
As Sound Transit models its operations, it has faced hurdles related to inconsistent interpretations of codes, such as those encountered in the City of Bellevue in relation to national fire code applications. Although legislative interpretations may diverge, it appears Sound Transit’s customary standards may lean towards an excessively rigorous interpretation compared to their global counterparts. Notably, assessments of Canadian fire code interpretation indicate major deviations compared to European methods, suggesting similar outcomes might exist for interpretations surrounding new American transit infrastructure.
The vast intended applicability of the National Fire Protection Association’s NFPA 130 standards enhances the perplexity of diverging interpretations.
Stakeholder Influence in Design
Sound Transit is making strides to reduce stakeholder-driven design influences, implementing standardized designs in which influence is minimized. Stakeholders can be a diverse group ranging from employees wishing for more amenities to local jurisdictions exerting pressures to customize station designs. Such pressures frequently trigger compliance with local jurisdictional objectives that do not align with overarching project aims.
Innovative Design Solutions for Sound Transit
Amid rising costs and delays in ST3 extensions, Sound Transit is re-evaluating its agency approach. Initial signs of improvement in project delivery, evident with the West Seattle Link, could generate savings amounting to hundreds of millions from each design to construction phase. One highly promising avenue for enhancing efficiency is the adoption of Reference Class Forecasting (RCF), a method of project management that evaluates a body of similar projects to draw on valuable insights for honing design efficiency while providing more accurate cost projections.
Reference Class Forecasting can mitigate design inertia, unnecessary regulatory compliance, and complex stakeholder modifications. By developing a project library that classifies cost drivers and risk elements, Sound Transit can systematically address issues that influence project size and scope, providing a formula for standardized transit infrastructure delivery.
While Ballard Link may confront specific engineering hurdles, the excessive size and depth of the West Seattle Junction station point toward symptoms of scope creep, underscoring the necessity for RCF application. A contemporary station depth of 70 feet contrasts sharply with proposed stations from two decades ago, which commonly operated at 40 feet deep, illustrating a concerning trend in underground construction.
Why, for example, is the standard cut-and-cover station design proposed at 90 feet deep rather than adhering to previously implemented standards?
Why are platform widths expanding from a historical norm of 24 feet to a current standard of 34 feet? And what tangible benefits are derived from such excessive station dimensions? Considering excavation costs exponentially grow with depth, reducing proposed depths for cut-and-cover stations could significantly curtail overall project expenditures.
Sound Transit’s shift toward increased station dimensions from the Sound Move initiative to ST3 can be traced back to these excessive specifications.
By implementing RCF, the ability to reduce size and design excesses by establishing clear design criteria is enhanced—bringing evidence-based decision-making into play. This approach directly addresses recommendations from the Technical Advisory Group regarding restoring trust and clarifying the roles and responsibilities of the Sound Transit Board and staff, while also offering concrete solutions.
US underground stations, being the priciest and riskiest construction components, stand to gain immensely from the re-engineering based on RCF principles. Those lessons can also inform other projects within the agency.
Necessary Actions for Sound Transit
To effectively reduce unnecessary station size, depth, and construction complexity, Sound Transit ought to undertake a thorough analysis of design elements in comparison to international projects, including non-English speaking contexts. The agency should systematically work toward a streamlined reduction in station size, depth, and intricacy informed by global best practices regarding codes and design standards within their standard station designs.
Furthermore, Sound Transit should establish specific criteria to objectively assess the viability of elevated, at-grade, trenched, or tunnel alignments. It is equally essential to develop clear methods for construction approaches, emphasizing the most efficient and least risky practices.
Applying these discourses retroactively to projects in the design and planning phases will deliver defensible estimates on project time, costs, and quality. For progressive initiatives, Sound Transit is encouraged to create reference classes that align service-focused planning with the infrastructure needed to meet those demands.
Leveraging RCF not only promises to ease station size and complexity but presents a significant opportunity to diminish construction time and costs. By adopting these insights, Sound Transit can provide board members with better access to information, ultimately enabling informed decision-making. Applying this methodology across planning initiatives can be key for nurturing sustainable systems for innovation and improvement.
In terms of regulatory frameworks, the authority local jurisdictions exert over Sound Transit’s station design standards remains counterproductive. Navigating diverse permitting processes across jurisdictions with varying motivations and requirements adds undue complexity to construction efforts. A recent proposal from Seattle Councilmember Maritza Rivera highlights the unpredictability and extra burdens such jurisdictions can inflict.
To remedy this, Sound Transit needs to request power from the State for self-approval of design decisions, or seek to engage in joint efforts with the Washington State Department of Transportation to leverage their institutional status in reducing engagements with local jurisdictions.
Moreover, pursuing state-level streamlining of transit project permits through enforcing compliance deadlines on third parties would yield substantial benefits. California’s recent SB 445 successfully demonstrates such reforms, passing out of their state senate with overwhelming support.
Enhancing reference classes for station and guideway designs to curtail over-compliance and stakeholder-driven design is only feasible if Sound Transit has the necessary authority to execute these reforms.
Moving Forward with Underground Stations
As costs associated with underground station development substantially contribute to the escalated expenses facing the West Seattle and Ballard Link initiatives, the MTA serves as an example of significant cost mitigation, but the lessons learned must extend beyond that.
CEO Constantine’s ambitions for realignment, urging a fresh approach to planning, and equipping board members with robust tools for strategic advancement, hinge on exploring alternatives to ‘scope and schedule’ adjustments.
Realizing the potential of reference class forecasting offers a systematic path toward minimizing costs and construction timelines. To empower such a strategy, granting Sound Transit authority at the state level is vital to initiate innovative solutions and minimize stakeholder abuses through preemptive code and permitting authority.
This crisis represents a pivotal moment for Sound Transit—one that the agency cannot afford to overlook. If you find resonance with this call for action, consider signing our letter to the Sound Transit Board.
image source from：https://www.theurbanist.org/2025/06/16/op-ed-shrinking-sound-transits-oversized-stations-could-save-hundreds-of-millions/
