Transport mode parameters

Road grades

Maintenance and demolition are percentages of the recorded build cost; maintenance is charged annually, spread monthly. Adding lanes multiplies cost and capacity:

Build cost = base cost × distance × lane multiplier × terrain factor. The terrain factor ranges from ×1.0 over flat ground to ×5.0 across extreme elevation change; water crossings add a separate bridge or tunnel cost on top.

Grades E, R, N and P can be tolled (E and R start tolled by default). A tolled link costs 10% more to maintain and is treated as 10% more saturated for congestion, so it reaches congested conditions earlier than an equivalent free road.

Railway grades

Track cost multipliers: 1 track ×1.0, 2 tracks ×1.9, 4 tracks ×4.5. A station is charged once per settlement and grade — extending from an existing same-grade station is free at that end.

A railway’s binding service limit is its daily train-path slots, shared by all operating lines using the link:

Train ferries host 6 round trips per day. Link capacity everywhere else in the model — including the saturation map — is derived from these same slots: a full timetable of maximum-length (60-car) trains counts as 100%.

Rail operating lines

Directional monthly capacity = cars × per-car capacity × daily round trips × 30. Rolling stock is bought with cash when the line opens and is recorded as a depreciating asset.

Automatic fare stances

Fares are automatic: the stance sets the band, utilization moves the fare within it, and above 85% utilization a break-even floor phases in so busy balanced and commercial lines cover their operating cost. Stance changes take effect at the next quarter.

Water routes and ports

Operating cost = $500,000 fixed per month + $45 per km per sailing × 30 days. The fixed part continues while a route is suspended. Frequency is 1–30 sailings per day; capacity is held per direction. Passenger and cargo fares are per-distance rates you set yourself (0–10 each), with a suggested value offered alongside.

Port terminals (three levels each)

Upgrading a terminal costs the price difference to the next level. Ports charge handling fees of $2 per passenger and $12 per cargo unit, and pay a congestion surcharge that grows quadratically above 100% utilization.

Ferry links: a car ferry costs $30M + $100K/km and behaves as an N-grade road (480 PCU, 20 km/h); a train ferry costs $60M + $200K/km and behaves as S-grade rail (300 PCU, 30 km/h).

Airports and air routes

One daily round trip consumes two movements at each endpoint. Upgrading an airport costs 80% of the build-cost difference. Seats per flight follow the lower of the two endpoint grades: 80 / 150 / 210 for passenger services, 60–170 seats plus 6–18 cargo units for mixed, 18 / 36 / 60 units for cargo.

Route setup costs $500,000 per km, with no distance limit. Airline operations are private; the public account receives a flat $35 charge per completed air journey (transfers do not multiply it) and pays airport maintenance of 1.8% per year (2.4% for hubs).

Air service is organized as airport-pair markets, each holding six independently scheduled buckets — passenger, mixed and cargo, in commercial and government-subsidized variants. Schedules are requested in whole weekly round trips and are limited by the lower endpoint grade, both airports’ shared movement budgets and, for subsidized service, the authorized cap and available fund.

Asset accounting

An overhaul bill equals one full interval of depreciation, spread evenly over the window that follows each anniversary of the build month. Interval and window move together, so every mode bills the same monthly intensity — an airport's longer 15-year cycle changes its rhythm, not how hard each month bites. Depreciation and the overhaul bill are both measured against what the asset would cost to build today: each asset records the construction price level of its own build year, and the current level is divided by it. Renewal restores book value up to that replacement cost, which in a nation whose construction costs have risen sits above the original purchase price. Road and rail earn no book-value return; only water and air assets pay the small monthly asset tax shown.

National Income bands

National Income is the band shown in the HUD and the My Country panel. It is decided by national GDP per capita alone — not by the development score, and not by revenue — and it sets the loan interest rate, the government grant rate and the income-sensitivity of several costs and recommended charges. A nation can hold a high development score and still sit in a low income band, or the reverse.

The grant rate is applied before the service and accessibility adjustments described in Where public money comes from; the earned share never falls below 30% of it.

Loans

Rates follow the National Income band in the table above. Terms: 5, 10, 20 or 30 years, amortized monthly; existing loans keep their agreed rate. Borrowing limit = the principal whose monthly payment, added to the payments already owed, reaches 80% of the trailing 12-month net operating cash flow — computed for the selected term and rate, then rounded down to a whole million. Neither GDP nor asset book value backs borrowing. With no full year of ledger history, a smaller fallback based on the current government grant applies; with net operating cash flow at or below zero, the limit is zero. When the fund cannot cover the next payment, debt restructuring extends outstanding loans up to a capped maximum term, paid for in additional interest and forgiving no principal.

The traffic model’s units

• The model month is 30 days (720 hours).
• Capacity is measured in passenger-car units (PCU): one passenger movement = 1 PCU; one cargo unit = 2.5 PCU on roads, 2 PCU on rail.
• Congestion compares assigned flow with a peak-equivalent monthly allowance (180 design hours per month); the absolute monthly throughput and billing ceiling uses the full 720 hours. See Travel demand, traffic and capacity.
• Each direction of a link has its own capacity; billing counts movement in both directions.

Cost indexing to the economy

Construction and operating costs scale with the nation’s trailing 12-month GDP per capita, relative to a $10,000 base. The multiplier rel = trailing GDP per capita ÷ 10,000:

A wealthy nation therefore pays up to about 2.5× base rail construction and 3× base rail operating costs, while road construction never rises above 1.45×.

Related reading

• What your transport network costs — the whole-life cost model these numbers feed.
• Transport lines and map styles — how grades appear on the map.