Audit of the traffic forecasting model for the Paris 2024 Olympic and Paralympic Games

The reception of Paris 2024 Olympic and Paralympic Games represents an unprecedented logistical challenge for the Île-de-France transport network.
In order to assess the capabilities of the system and to size the necessary resources, a multimodal traffic forecasting model was developed to simulate flows related to spectators, delegations, media and daily travel.

Explain was requested by Île-de-France Mobilities To drive a independent audit of this tool, in order to validate its methodological principles and the robustness of the results.

The mission was structured around four main components:

1. Model structure analysis
   • Study of the scope, modeling hypotheses and demand structure.
   • Verification of the consistency between the databases used (surveys, ticketing, attendance scenarios).
2. Control of scenario hypotheses
   • Critical analysis of supply hypotheses (capacities, schedules, modal complementarity).
   • Assessment of reliability conditions according to periods (JO, JOP, post-event).
3. Recalibration and sensitivity tests
   • Verification of demand calibrations and intermodal flows.
   • Analysis of the sensitivity of the results to the variation of the assumptions of attendance and mode of access.
4. Recommendations and improvement of the model
   • Identification of points of vigilance and proposals for methodological adjustments.
   • Elaboration of a detailed audit report accompanied by an executive summary for decision makers.

Explain's work has made it possible toensure scientific and operational compliance of the model and to strengthen trust between the various institutional actors (IDFM, COJOP, RATP, SNCF, Regional Prefecture).

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The purpose of the audit was to secure the use of the model in the decision-making process linked to the management of mobility during the Games.
The specific objectives were to:

• Check the structural and behavioral coherence the traffic model;
• Identify the potential discrepancies or biases in the hypotheses and results;
• Suggest concrete methodological improvements and hierarchical;
• Strengthen the transparency and traceability modeling in a context of national challenges.

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The intervention ofExplain allowed Île-de-France Mobilities to have a independent and reasoned evaluation of the reliability of the JOP 2024 model.The findings contributed to secure operational decisions and to better coordinate actions between transport operators and state services. The audit methodology also served as internal reference for the validation of future planning models from IDFM.

This mission illustrates the ability toExplain to intervene on projects with a high national challenge, by mobilizing its expertise in modeling, evaluation and methodological audit.The audit of the traffic model of Paris 2024 Olympic and Paralympic Games made it possible to guarantee the scientific robustness and transparency forecasts, essential conditions for the success of an event of this magnitude.