To assess the appropriate level of hybrid bond issuance for Ferrovial S.A. for the 18 months following December 31, 2022, we analyze the financial position provided:

1.  **Capital Structure and Leverage:** As of January 1, 2023, Ferrovial shows total Equity of 6.354 billion EUR. The non-current portion of borrowings is 10.776 billion EUR, with total current borrowings of 877 million EUR. The company has a significant infrastructure asset base (approx. 13.667 billion EUR) that requires ongoing capital investment.
2.  **Financial Metrics:** Ferrovial has shown a consistent revenue increase (from 6.911 billion EUR in 2021 to 7.553 billion EUR in 2022). While operating profit (423 million EUR) and net profit (302 million EUR) have remained positive, the company maintains a high level of debt associated with infrastructure projects (over 7.9 billion EUR combined current/non-current).
3.  **Capex and Strategic Needs:** Ferrovial operates in the transportation infrastructure sector, which is capital-intensive. The reported investment in infrastructure projects for 2022 was 784 million EUR. Maintaining or expanding this infrastructure often requires significant, long-term capital commitments.
4.  **Rationale for Hybrids:** The company's current hybrid structure already exists (Other Equity Securities at 508 million EUR). Using hybrid instruments allows the company to optimize its leverage metrics without diluting existing shareholders, providing "rating headroom" which is beneficial for companies in capital-intensive sectors like transportation infrastructure.
5.  **Market Environment:** The 2022 market data shows a significant increase in swap rates compared to 2020/2021 (the 5Y swap rate rose to ~1.726%). Issuing debt in this environment is more expensive. Hybrid bonds, while also costly, provide equity-like characteristics that help preserve investment-grade credit metrics, which are vital for a company with such a large infrastructure investment pipeline.
6.  **Recommendation:** Given Ferrovial’s ongoing need for capital to support infrastructure assets, a moderate-to-high level of hybrid support is justified to maintain financial flexibility and preserve credit ratings during this period of rising interest rates and active capital investment. The range of 11.25% aligns with a profile requiring significant leverage management to support a large investment pipeline while preserving investment-grade ratings.

<answer>11.25%</answer>