Looking Ahead: Scenario Ranges for TEU Growth
A transparent stress-test of long-range container throughput assumptions for the Ports of Savannah (GPA) and Charleston (SCPA). These are scenario ranges (not point forecasts) built from the same baseline TEU inputs and a shared modeling structure.
Why this page exists.
Long-range port plans often present one “expected” outcome. This page presents multiple plausible ranges instead—because
assumptions (rail conversion, landside constraints, capacity delivery timing, competition, and disruption cadence) do the real work.
If a forecast is wrong, it’s usually because the assumptions were never stress-tested in public.
Executive Summary
What was done.
A single, structured forecasting prompt was used to evaluate long-range container throughput for the Ports of Savannah (GPA) and Charleston (SCPA).
The same historical TEU baselines, scenario structure, and modeling logic were provided to four independent AI models (ChatGPT, Gemini 3, Claude, and Grok)
to test how sensitive long-range outcomes are to execution, capacity, landside constraints, competition, and disruption risk.
Download the full model outputs (PDF)
PDF
Each model used the same baseline TEUs and the same scenario structure. PDFs are provided for full transparency.
Model Charts
Method note.
The prompt was designed to prevent “best-case storytelling.”
Each AI model was required to:
- Use the same historical TEU baselines
- Present multiple scenarios instead of a single forecast
- Explicitly identify which assumptions drive outcomes
- State what must occur for high or low outcomes to materialize
Below are two chart sets (ChatGPT + Gemini 3). Claude’s contribution is used for governance-style conditions and leadership questions, with full Claude output linked above.
Model A — ChatGPT
Port of Savannah (GPA). Scenario band outlook to 2045 (ChatGPT).
Port of Charleston (SCPA). Scenario band outlook to 2045 (ChatGPT).
Model B — Gemini 3
Port of Savannah (GPA). Scenario band outlook to 2045 (Gemini 3).
Port of Charleston (SCPA). Scenario band outlook to 2045 (Gemini 3).
Cross-Model Synthesis — Where the forecasts converge
The table below summarizes what each model implies for total container throughput in 2035 and 2045. Midpoints reflect the center of each model’s Base scenario band; ranges span Disruption (low) through High outcomes. These are not blended averages — they are shown side by side to highlight agreement and divergence.
| Model | Port | 2035 Midpoint (Range) |
2045 Midpoint (Range) |
|---|---|---|---|
| ChatGPT | Savannah (GPA) | ~9.0 M (6.8–11.2) | ~11.5 M (7.8–15.5) |
| Charleston (SCPA) | ~4.0 M (3.1–4.8) | ~5.0 M (3.7–6.5) | |
| Gemini 3 | Savannah (GPA) | ~9–10 M (7–12) | ~12–14 M (8–18) |
| Charleston (SCPA) | ~4.0 M (2.8–5.5) | ~5.9 M (3.8–9.0) | |
| Claude | Savannah (GPA) | ~9.0 M (6.8–11.2) | ~11.5 M (7.8–15.5) |
| Charleston (SCPA) | ~4.0 M (3.1–4.8) | ~5.0 M (3.7–6.5) | |
| Grok | Savannah (GPA) | ~9.0 M (6.5–12.0) | ~13.0 M (8.0–18.0) |
| Charleston (SCPA) | ~4.0 M (2.8–5.5) | ~5.9 M (3.8–9.0) |
What this comparison shows is not four different “answers,” but four variations on the same conditional reality.
Across independent models, the midpoints cluster within a relatively narrow band, while the ranges widen primarily due to execution risk rather than uncertainty about demand. In every case, outcomes near the high end require timely delivery of capacity, meaningful rail conversion, and sustained landside fluidity. Outcomes near the low end emerge when those conditions slip or when disruptions compound over time. The implication is straightforward: long-range TEU projections are best understood not as predictions, but as stress tests of whether critical operational assumptions are likely to hold.
Across independent models, the midpoints cluster within a relatively narrow band, while the ranges widen primarily due to execution risk rather than uncertainty about demand. In every case, outcomes near the high end require timely delivery of capacity, meaningful rail conversion, and sustained landside fluidity. Outcomes near the low end emerge when those conditions slip or when disruptions compound over time. The implication is straightforward: long-range TEU projections are best understood not as predictions, but as stress tests of whether critical operational assumptions are likely to hold.
What assumptions do the most work
- Rail conversion and inland throughput: Effective utilization depends on rail share and intermodal reliability, not just berth capacity.
- Capacity delivery timing: Expansions only affect throughput if delivered on schedule without chronic productivity loss.
- Landside constraints: Drayage, gate systems, and corridor congestion often cap throughput ahead of terminal limits.
- Competition and carrier routing: Jacksonville, Norfolk, or NY/NJ network shifts can change market share sooner than most plans assume.
- Disruption cadence: Recurring trade shocks, labor disruptions, and weather events have cascading, multi-year effects on throughput ranges.
What must be true (conditions, not promises)
High-case outcomes require
- On-time delivery of key capacity expansions with minimal productivity loss.
- Significant rail/inland throughput scaling backed by binding Class I commitments.
- Limited competitive diversion and stable carrier routing.
- Demand conditions that avoid persistent compression of containerized imports.
Disruption-case outcomes occur when
- Capacity expansions slip and landside constraints become enduring.
- Trade friction and supply-chain shocks recur frequently.
- Carriers reroute volumes toward more fluid gateways over multiple seasons.
- Weather or corridor failures reduce effective utilization repeatedly.
Questions port leadership should be able to answer
For GPA leadership (Savannah)
- Does your 2035 plan assume 50%+ rail share, and what commitments support it?
- If expansions slip 2–3 years, what is the revised TEU range and downside plan?
- What share is assumed for Jacksonville/Norfolk cargo by 2035?
- At what throughput does Garden City utilization become binding?
- Which leading indicators would trigger a capital plan rebaseline?
For SCPA leadership (Charleston)
- What rail conversion percentage is assumed for 2035 and how is it secured?
- If key phases slip, what fallback capacity and market-share plan exists?
- What TEU level makes the drayage corridor binding, and which fixes are fully funded?
- What market share loss is assumed if competitors gain fluidity faster than Charleston?
- Which leading indicators would trigger a capital plan reset?
Notes.
Charts and PDFs are presented side by side for transparency. The purpose is not to claim certainty about 2045,
but to force the underlying assumptions into the open so that public planning can be evaluated and stress-tested.