Based on the financial facts provided for FERROVIAL SA for the fiscal year ended December 31, 2022, and the macroeconomic context, we can evaluate the company's need to utilize hybrid bonds as follows:

1. **Current Hybrid Utilization and Capital Structure**:
   - Ferrovial reported "Other Equity Securities" of 508 million EUR as of January 1, 2023, which corresponds to its outstanding perpetual subordinated bonds (hybrids).
   - The company's Total Debt stands at approximately 11.65 billion EUR (10.77 billion EUR noncurrent + 877 million EUR current). 
   - Total Equity is 6.35 billion EUR. 
   - Total Adjusted Capital (Total Debt + Total Equity) is roughly 18.0 billion EUR.
   - The existing 508 million EUR in hybrid bonds represents approximately 2.8% of Total Adjusted Capital. This directly falls into the lower utilization tier and eliminates the 0% option (which implies no current hybrid in the capital structure).

2. **Refinancing Needs and Liquidity**:
   - Ferrovial has massive liquidity. Its reported "Cash and Cash Equivalents" is 5.13 billion EUR.
   - Notably, cash excluding infrastructure projects (4.96 billion EUR) exceeds debt excluding infrastructure projects (3.68 billion EUR). The holding company effectively sits in a net-cash position.
   - Operating cash flows (1.0 billion EUR) easily cover organic capex and investments in infrastructure projects (784 million EUR). This underscores that the company has very low/moderate funding needs and no pressing necessity for a major capital structure transformation.

3. **Leverage Optimization and Rating Flexibility**:
   - Due to the strong corporate balance sheet and massive liquidity buffer, Ferrovial faces no significant leverage pressure.
   - The current modest layer of hybrids provides mild leverage optimization and "limited but useful rating flexibility" without heavily burdening the capital structure.

4. **Cost of Debt (Market Data)**:
   - Entering 2022, interest rates climbed sharply. The 5Y Swap Curve spiked from negative territory (-0.264 in 2021) to 1.726 in 2022. 
   - The subordinated-to-senior spread delta (Sub-Sen Delta) widened significantly to 2.295 in 2022. Under these conditions, the cost of issuing *new* hybrids would materially increase the current cost of debt, creating a strong economic disincentive to expand hybrid utilization up to the 7.5% or 11.25% tiers.

**Conclusion**: 
Ferrovial already has a hybrid instrument in place, accounting for ~2.8% of its total adjusted capital. Due to its phenomenal cash reserves, robust operating cash flow, and the surging cost of subordinated debt in 2022, there is no fundamental rationale to expand hybrid issuance. The company's profile perfectly aligns with maintaining a small hybrid buffer for mild rating flexibility under the 3.75% guideline.

<answer>3.75%</answer>