Strengthening urban mobility: how Metro Ligero Oeste integrates GRESB into light-rail operations in Madrid

Metro Ligero Oeste, S.A. is a public-private partnership and the concession holder of the ML2 and ML3 light-rail lines, connecting Madrid with Boadilla del Monte, Alcorcón, and Pozuelo de Alarcón since July 2007.

Looking ahead to 2026 and beyond, MLO’s sustainability priorities include: 

• Reducing greenhouse gas emissions through energy optimization, improved traction system efficiency, and increased use of renewable energy 
• Strengthening asset awareness of climate-related physical risks through scenario analysis, long-term investment planning, and adaptive maintenance strategies 
• Enhancing operational performance and user experience through digitalization, safety, accessibility, and transparent governance 

Metro Ligero Oeste (MLO) began participating in the GRESB Infrastructure Asset Assessment in 2018 under the stewardship of Aberdeen, with the objective of benchmarking its sustainability performance against international peers, strengthening reporting transparency, and adopting established practices in governance and asset management. This decision reflected a broader ambition to move beyond isolated sustainability initiatives toward a more organized, systematic, and measurable approach that contributes to asset management processes and decisions. 

Over time, GRESB participation evolved from an annual reporting exercise into a tool for planning and governance activities, with results integrated into governance cycles to define key performance indicators (KPIs) and inform capital expenditure and maintenance planning. 

In practice, GRESB insights are applied across operations, procurement, and governance. Performance indicators have guided investments to improve energy efficiency, including initiatives to optimize traction energy consumption, while health and safety results inform adjustments to maintenance and cleaning plans. Emissions- and waste-related KPIs are embedded in procurement specifications, reinforcing sustainability considerations within the supply chain where relevant. 

“The continued use of GRESB allows us to track performance year after year, adjust priorities based on evidence, and support operational performance across a public-private transport asset, while keeping our objectives, policies and performance monitoring aligned,” said José Luis López Jiménez, IT Manager at MLO. 

This integrated, data-driven approach—aligned with Aberdeen’s global sustainability strategy—resulted in MLO achieving a GRESB Score of 100 points and a five-star rating in 2025. 

As a public-private urban light-rail operator serving Madrid and surrounding municipalities, MLO operates in a complex stakeholder environment that includes public authorities, concession partners, contractors, other transport operators, and users. Key challenges include aligning performance expectations while maintaining regulatory compliance, service continuity, safety, and accessibility. 

The public-private partnership model also creates opportunities for joint planning with public administrations, supporting system integration, interoperability, and access to co-financed sustainability initiatives. MLO addresses these dynamics through governance based on open channels of communication, regular reporting, and structured coordination with the Madrid Regional Transport Consortium and local municipalities. 

Sustainability expectations are embedded across these relationships, including within procurement and contractor management. Sustainability requirements—covering energy efficiency, occupational health and safety, waste management, and compliance with environmental certifications—are incorporated into technical specifications, contractor selection criteria, and contractual clauses. During contract execution, supplier and contractor performance is monitored through audits, operational controls, and regular sustainability reporting, supporting risk oversight, compliance activities, and ongoing enhancements across the supply chain. 

GRESB data and year-on-year performance analysis support this approach by providing a useful comparison point for assessing governance practices, stakeholder engagement, and supply-chain performance against international peers.

Climate scenario analysis forms part of MLO’s approach to resilience planning. The asset uses scenario analysis to assess and manage physical climate risks such as heat waves, flooding, and extreme weather events across both infrastructure and route networks.  

This approach combines historical incident data, climate projections, and asset vulnerability mapping to identify critical points and anticipate potential operational impacts. The findings inform planning and investment decisions, including prioritizing drainage improvements in sensitive areas, using materials more resistant to high temperatures, reinforcing ventilation systems, and adapting maintenance cycles following extreme weather events. 

Climate scenario insights are also integrated into long-term investment planning, insurance coverage reviews, and the updating of emergency response protocols. In addition, the results are incorporated into MLO’s annual SWOT analysis, linking climate risk identification directly to defined objectives and improvement actions within the strategic plan. 

Insights from the GRESB assessment process support this work by reinforcing a more consistent consideration of climate-related risks and the integration of resilience considerations into long-term planning and investment decisions. 

“Continued participation in GRESB plays an important role in how we monitor performance and drive continuous improvement, providing an objective framework to measure progress, validate results, and guide investment decisions that deliver measurable environmental, social, and operational improvements,” concluded López Jiménez.