To determine the appropriate utilization of hybrid bonds relative to the 15% S&P Global Ratings' equity credit cap, we evaluate Ferrovial's financial position and market environment as of the end of 2022:

1. **Capital Structure Analysis**:
   - Total Assets: 26,284,000,000 EUR
   - Equity (Total): 6,354,000,000 EUR
   - Noncurrent Liabilities: 13,142,000,000 EUR
   - Current Liabilities: 5,378,000,000 EUR
   - Total Debt (Borrowings): Current (877,000,000 EUR) + Noncurrent (10,776,000,000 EUR) = 11,653,000,000 EUR
   - Total Adjusted Capital (Debt + Equity): 11,653,000,000 + 6,354,000,000 = 18,007,000,000 EUR
   - 15% S&P Hybrid Cap = 0.15 * 18,007,000,000 = 2,701,050,000 EUR

2. **Ferrovial's Current Position**:
   - The company reports "Other Equity Securities" of 508,000,000 EUR (as of 2023-01-01), which is significantly below the 2.7 billion EUR threshold.
   - Ferrovial has demonstrated strong liquidity (Cash: 5.13 billion EUR) but carries significant noncurrent infrastructure debt (approx. 7.9 billion EUR).
   - Market conditions in 2022 saw a sharp rise in the 10Y Swap curve (from 0.053% in 2021 to 1.927% in 2022) and an increase in bond yields (iBoxx non-financial IG from 1.298% to 2.295%), indicating that issuing new debt has become more expensive.

3. **Strategic Consideration**:
   - Given the rising interest rate environment in 2022 and the need to maintain a strong credit profile while funding long-term infrastructure projects, there is clear capacity to increase hybrid capital. However, utilizing the full 100% of the S&P cap would be aggressive and potentially inefficient from a cost-of-capital perspective. A balanced approach (50% utilization of the allowable cap) allows the company to benefit from the equity credit feature to support its credit ratings while avoiding over-reliance on hybrid instruments.

<answer>50%</answer>