I need to analyze Ferrovial's capital structure and determine the appropriate reliance on hybrid bonds. Let me examine the key financial data.

## Key Financial Analysis

### Balance Sheet Structure (2023-01-01)
- Total Assets: €26,284M
- Total Equity: €6,354M (24.2% of assets)
- Total Liabilities: €19,930M (75.8% of assets)
  - Noncurrent liabilities: €13,142M
  - Current liabilities: €5,378M

### Equity Composition
- Equity attributable to owners: €4,113M
- Noncontrolling interests: €2,241M (35.3% of total equity)

### Debt Structure
- Noncurrent borrowings: €10,776M
  - Infrastructure projects debt: €7,893M
  - Excluding infrastructure projects: €2,883M
- Current borrowings: €877M

### Key Observations

1. **High leverage**: Debt-to-equity ratio is approximately 3:1, indicating significant reliance on debt financing.

2. **Infrastructure project financing**: A substantial portion of debt (€7,893M noncurrent + €74M current = €7,967M) is tied to specific infrastructure projects with likely ring-fenced cash flows. This is project finance with limited recourse.

3. **Perpetual subordinated bonds**: The company already has some hybrid capital in its structure. In 2022-2023, there was a -€8M impact from perpetual subordinated bonds, and in 2021-2022, -€7M. These are small amounts relative to total capital.

4. **Interest rate environment**: The swap curves show significantly rising rates in 2022 (1.7-1.9% for 5-10Y vs. negative/very low in 2020-2021). This makes fixed-rate hybrid bonds relatively more attractive vs. floating bank debt.

5. **Credit spread context**: The iShares Core Euro Corp Bond yield was 1.085% in 2022 (average), with sub-senior delta of 0.2% for non-financial IG. This suggests hybrid bonds would yield roughly 1.3-1.5% above senior debt.

6. **Business model characteristics**:
   - Heavy infrastructure/concession assets with long-term, stable cash flows
   - Significant noncontrolling interests (35%) suggesting joint ventures and project-specific equity
   - High intangible asset model investments (€13,504M) - typical of concession/P3 models

### Hybrid Bond Suitability Assessment

**Arguments for hybrid bonds:**
- Long-dated, stable infrastructure cash flows match the perpetual/long-dated nature of hybrids
- Rising interest rate environment favors locking in long-term rates
- Infrastructure companies are classic hybrid issuers due to asset longevity
- Can improve equity credit from rating agencies without diluting existing shareholders
- Tax efficiency of interest deductions

**Arguments against excessive hybrid reliance:**
- Already high leverage (75.8% debt/assets)
- Significant noncontrolling interests create complexity
- Need to maintain financial flexibility for project development
- Hybrid coupons are typically higher than senior debt (roughly 200-300bps spread for 50% equity credit)

### Optimal Hybrid Allocation

Given Ferrovial's profile:
- **Infrastructure concession company** with long-term stable revenues
- **Already leveraged** but with project-finance ring-fencing
- **Need to maintain investment grade rating** for infrastructure project access
- **Rising rate environment** makes fixed-rate hybrids attractive vs. floating bank debt

For infrastructure companies, hybrid bonds typically receive 50% equity credit from rating agencies. A moderate hybrid allocation of around **25%** of total capital would:
- Provide rating agency equity credit benefit
- Not over-leverage the structure
- Maintain financial flexibility
- Match the long-duration asset base
- Be consistent with European infrastructure peer practice

Higher allocations (50-75%) would be more typical of regulated utilities with extremely stable cash flows, whereas Ferrovial has construction and development risk. Lower allocations (0%) would miss the opportunity to optimize capital structure for a company with natural hybrid-compatible assets.

<answer>25%</answer>