Ferrovial in 2022 shows large asset base and substantial long-term debt related to infrastructure projects, with significant noncurrent borrowings and high gearing when including project financing. The company also has sizable noncurrent liabilities and some higher leverage driven by infrastructure financing, though cash flows from operations improved year-over-year in 2022. Hybrid bonds could help manage balance sheet leverage by adding non-debt-like equity credit, potentially stabilizing adjusted leverage metrics and supporting ratings in the face of ongoing capex and project financing needs. However, the company already carries meaningful leverage from project finance and noncurrent borrowings, and there is no indication of an immediate liquidity crisis; also, there is no current hybrid in the structure as of the given data. Rating benefit from hybrids typically requires careful sizing to avoid excessive cost of debt and ensure material improvement in adjusted leverage.

Given the starting point and the guideline checklist:
- 0%: would imply strong rating stability with no need for leverage optimization. This seems unlikely given heavy project financing and upcoming capex/maintenance in infrastructure.
- 3.75%: mild leverage optimization and limited rating flexibility; could be relevant if refinancing needs are moderate and capex is manageable.
- 7.5%: meaningful improvement in adjusted leverage, with rating headroom; aligns with a medium to high capex/investment cycle.
- 11.25%: high capex/investment needs and significant leverage pressure; ratings highly dependent on capital structure optimization.
- 15%: transformational needs; substantial rating support required.

Ferrovial appears to be in a phase with substantial capex and project financing, suggesting moderate to strong refinancing and growth needs, with a need to preserve ratings. Therefore hybrid issuance around the midpoint would be reasonable, but with governance to maintain manageable interest costs and ensure improvement in adjusted leverage. I would propose 7.5% of total adjusted capital as the target, balancing leverage improvement with cost impact.

Answer: <answer>7.5%</answer>