How the France carte grise calculator is verified
Inputs
| Input | Field | Type |
|---|---|---|
| Puissance fiscale (CV) | fiscalCV | number |
| Région | region | string |
| Tarif si « Autre » (EUR / CV) | customRate | number |
The formula
Each derived value below is computed by the Valem engine from the expression shown, in this order. Nothing else runs — there is no hidden code path.
| Derived value | Field | Formula (JSONata) |
|---|---|---|
| Tarif régional (EUR/CV) | regionalRate | ($s := region; $s = 'IDF' ? $const.rateIDF : $s = 'ARA' ? $const.rateARA : $s = 'OCC' ? $const.rateOCC : $s = 'BRE' ? $const.rateBRE : $s = 'NOR' ? $const.rateNOR : customRate) |
| Taxe régionale | taxeRegionale | $round(fiscalCV * regionalRate, 2) |
| Frais fixes (gestion + acheminement) | fraisFixes | $round((fiscalCV >= 0 ? $const.redevanceGestion + $const.acheminement : 0), 2) |
| Coût carte grise | total | $round(taxeRegionale + fraisFixes, 2) |
Rates and thresholds
The expressions above read these as $const. They are the figures the annual refresh replaces, so they live as data rather than being written into the formulas — which is what makes a year-on-year change a one-line diff instead of an edit to arithmetic.
| Constant | Value |
|---|---|
redevanceGestion | 11 |
acheminement | 2.76 |
rateIDF | 68.95 |
rateARA | 43 |
rateOCC | 58 |
rateBRE | 60 |
rateNOR | 60 |
Test vectors (3)
Every case is executed against this model on each build, by the Java engine and independently by a JavaScript one. A mismatch of a single cent fails the build, so the page cannot ship advertising a figure the model no longer produces.
Case 1 — C1 5 CV at 51 EUR/CV
given fiscalCV | 5 |
|---|---|
given region | autre |
given customRate | 51 |
expect taxeRegionale | 255 |
expect fraisFixes | 13.76 |
expect total | 268.76 |
Case 2 — C2 7 CV at 51 EUR/CV
given fiscalCV | 7 |
|---|---|
given region | autre |
given customRate | 51 |
expect taxeRegionale | 357 |
expect total | 370.76 |
Case 3 — C3 5 CV en Île-de-France — le tarif régional le plus élevé de France
given fiscalCV | 5 |
|---|---|
given region | IDF |
expect regionalRate | 68.95 |
expect taxeRegionale | 344.75 |
expect total | 358.51 |
Sources
- Coût de la carte grise — service-public.fr · checked 2026-08-02
- Malus écologique — service-public.fr · checked 2026-08-02
Check it yourself — and reuse it
The whole model as JSON — inputs, outputs, formulas, vectors and sources in one re-runnable document.
This model is published under CC BY 4.0: use it, adapt it, build on it, with attribution. The licence covers the model — the expression of each rule and the arrangement of the catalog. The rates and thresholds are law, and nobody licenses those; the sources above are where they come from.
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