To determine S&P's credit trend for FERROVIAL SA from 2021 to 2022, we follow the prescribed workflow, applying the general corporate methodology with considerations for the Transportation Infrastructure sector.

**Step 1: Identify the Relevant Industry**
FERROVIAL SA operates in the "Transportation Infrastructure" sector (including toll roads and airports). We apply the baseline corporate formulas, making sure to include dividends received from equity investments (a standard S&P proxy for cash flow generated by infrastructure joint ventures).

**Step 2: Estimate 2021 Adjusted EBITDA**
We reconstruct EBITDA using continuing operations:
- Gross Profit / EBIT roughly equals the reported Operating Profit before impairments.
- Profit From Operations Before Impairment and Disposals (EBIT): €340M
- Amortisation Expense: €270M
- EBITDA = €340M + €270M = €610M (which perfectly matches the reported Gross Profit of €610M).
- Plus Dividends Received from JVs and Associates: €272M
- **Adjusted EBITDA (2021) ≈ €882M**

**Step 3: Estimate 2021 FFO (Funds From Operations)**
- Adjusted EBITDA: €882M
- Net Cash Interest Paid = Interest Paid (€295M) - Interest Received (€3M) = €292M
- Cash Taxes Paid: €155M
- **FFO (2021)** = €882M - €292M - €155M = **€435M**

**Step 4: Estimate 2021 Adjusted Debt**
- Reported Borrowings (Current + Noncurrent): €1,096M + €9,513M = €10,609M
- Leases (Current + Noncurrent): €58M + €115M = €173M
- Pension Deficit: €3M
- Hybrid Debt (50% of Perpetual Subordinated Bonds of €506M): €253M
- Less Eligible Cash & Equivalents: -€5,536M
- **Adjusted Debt (2021)** = €10,609M + €173M + €3M + €253M - €5,536M = **€5,502M**

**Step 5 & 6: 2021 Ratios**
- **Adjusted Debt / Adjusted EBITDA**: €5,502M / €882M = **6.24x**
- **FFO / Adjusted Debt**: €435M / €5,502M = **0.079 (7.9%)**

**Step 7: Estimate 2022 Adjusted EBITDA**
- Profit From Operations Before Impairments (EBIT): €429M
- Amortisation Expense: €299M
- EBITDA = €429M + €299M = €728M (Matches reported Gross Profit of €728M).
- Plus Dividends Received from JVs and Associates: €284M
- **Adjusted EBITDA (2022) ≈ €1,012M**

**Step 8: Estimate 2022 FFO**
- Adjusted EBITDA: €1,012M
- Net Cash Interest Paid = Interest Paid (€329M) - Interest Received (€47M) = €282M
- Cash Taxes Paid: €82M
- **FFO (2022)** = €1,012M - €282M - €82M = **€648M**

**Step 9: Estimate 2022 Adjusted Debt**
- Reported Borrowings (Current + Noncurrent): €877M + €10,776M = €11,653M
- Leases (Current + Noncurrent): €64M + €120M = €184M
- Pension Deficit: €2M
- Hybrid Debt (50% of Perpetual Subordinated Bonds of €508M): €254M
- Less Eligible Cash & Equivalents: -€5,130M
- **Adjusted Debt (2022)** = €11,653M + €184M + €2M + €254M - €5,130M = **€6,963M**

**Step 10 & 11: 2022 Ratios**
- **Adjusted Debt / Adjusted EBITDA**: €6,963M / €1,012M = **6.88x**
- **FFO / Adjusted Debt**: €648M / €6,963M = **0.093 (9.3%)**

**Step 12: Classify the Year-on-Year Credit Trend**
- **Signal 1 (Leverage):** 6.88x - 6.24x = **+0.64x**. Since this is ≥ +0.2x, the leverage signal is **Deteriorating**.
- **Signal 2 (Cash-flow coverage):** 0.093 - 0.079 = **+0.014 (+1.4 percentage points)**. Since this falls between -0.03 and +0.03, the cash-flow coverage signal is **Stable**.

*Conclusion:* Adjusted Debt increased significantly (~€1.46B rise in Net Debt due to higher borrowings and depleted cash) far outpacing the moderate ~€130M growth in EBITDA, leading to materially weakened leverage. When one signal is Deteriorating and the other is Stable, the aggregate framework rules stipulate overriding the Stable signal and adopting the directional shift. 

<answer>Deteriorating</answer>