System

Operator-queued system: {{entity:New Tyne Crossing Transport Appraisal System}}, a decision support system for evaluating options for a new crossing of the River Tyne in northeast England. This is a digital/analytical system operating within the DfT Transport Analysis Guidance framework, covering multi-modal demand modelling, traffic microsimulation, economic appraisal, environmental impact assessment, geospatial analysis, data management, and appraisal reporting. The system classified as {{hex:40A53B59}} — Synthetic, Intentionally Designed, Processes Signals/Logic, System-integrated, Rule-governed, Compositional, Normative, Temporal, Digital/Virtual, Institutionally Defined, Regulated, Economically Significant, and Ethically Significant. Status: scaffolded with 7 subsystems, 21 requirements, 15 trace links, and 2 diagrams.

Decomposition

Seven subsystems reflect the real functional architecture of a UK transport appraisal system for a major scheme:

• {{entity:Transport Demand Modelling Subsystem}} ({{hex:40B53358}}) — four-stage variable demand model with mode choice, consuming NTEM/TEMPro growth and Census JTW data
• {{entity:Traffic Microsimulation Subsystem}} ({{hex:40F53308}}) — junction/corridor-level Paramics/VISSIM-class simulation for 5-8 route option corridors
• {{entity:Economic Appraisal Engine}} ({{hex:40B53358}}) — WebTAG-compliant BCR/NPV computation with wider economic impacts per TAG Unit A2
• {{entity:Environmental Assessment Subsystem}} ({{hex:40A53B59}}) — air quality (DMRB LA 105), noise (LA 111), carbon (TAG A3), BNG (Environment Act 2021)
• {{entity:Geospatial Analysis Platform}} ({{hex:40E53159}}) — GIS-based constraint mapping, route option corridor analysis, OS MasterMap/LiDAR integration
• {{entity:Data Acquisition and Management Subsystem}} ({{hex:40A53358}}) — ATC/ANPR data collection, ETL pipelines, data quality assurance per TAG M1
• {{entity:Appraisal Reporting Subsystem}} ({{hex:40A57B59}}) — AST generation, five-case business case documents, distributional impact tables

The data flow is pipeline-shaped: Data Acquisition feeds the Demand Model, which feeds both Microsimulation (turning counts) and Economic Appraisal (time savings). Microsimulation feeds Economic Appraisal (journey time reliability) and Environmental Assessment (speed-emission profiles). Geospatial Analysis feeds Environmental Assessment (receptor locations, constraints) and Reporting (route plans). Economic Appraisal, Environmental Assessment, and Geospatial Analysis all feed into Reporting for AST and business case production.

flowchart TB
  DAM["Data Acquisition and Management"]
  TDM["Transport Demand Modelling"]
  TMS["Traffic Microsimulation"]
  EAE["Economic Appraisal Engine"]
  ENV["Environmental Assessment"]
  GEO["Geospatial Analysis Platform"]
  RPT["Appraisal Reporting"]
  DAM -->|Traffic counts, OD matrices| TDM
  TDM -->|Turning count matrices| TMS
  TDM -->|Time savings matrices| EAE
  TMS -->|Journey time reliability| EAE
  TDM -->|Traffic flows and speeds| ENV
  GEO -->|Receptor locations, constraints| ENV
  EAE -->|BCR, NPV, monetised benefits| RPT
  ENV -->|Environmental impact scores| RPT
  GEO -->|Route plans, constraint maps| RPT

Analysis

The {{entity:Economic Appraisal Engine}} shares 31 traits with the {{entity:Data Acquisition and Management Subsystem}} and 30 traits with the {{entity:Clinical Data Integration Subsystem}} from the hospital patient monitoring decomposition. This cross-domain parallel with clinical data integration is notable — both systems consume heterogeneous data sources, apply domain-specific regulatory validation rules, and produce auditable analytical outputs for decision-makers. The {{entity:Spatial Database}} from the emergency dispatch system also shares 30 traits, confirming the geospatial processing archetype across transport, emergency services, and environmental domains.

The environmental assessment subsystem received the same hex code ({{hex:40A53B59}}) as the parent system — both are rule-governed, institutionally defined, regulated analytical frameworks. This ontological similarity is correct: the environmental assessment is itself a self-contained appraisal system within the broader transport appraisal.

Requirements

Eight stakeholder requirements capture the real stakeholder landscape: DfT as funding body ({{stk:STK-NEEDS-001}}), statutory environmental compliance ({{stk:STK-NEEDS-002}}), public transparency ({{stk:STK-NEEDS-003}}), multi-modal assessment policy ({{stk:STK-NEEDS-004}}), distributional equity ({{stk:STK-NEEDS-005}}), analytical auditability ({{stk:STK-NEEDS-006}}), forecast robustness ({{stk:STK-NEEDS-007}}), and geospatial constraint coverage ({{stk:STK-NEEDS-008}}).

Thirteen system requirements derive from stakeholder needs with full traceability. Key examples: {{sys:SYS-REQS-001}} (BCR computation with current TAG Data Book values), {{sys:SYS-REQS-002}} (variable demand with six-mode choice), {{sys:SYS-REQS-003}} (microsimulation within 2km at 1-second timestep), {{sys:SYS-REQS-004}} (NO2/PM2.5 dispersion at 200m receptors), {{sys:SYS-REQS-006}} (10% Biodiversity Net Gain per Environment Act 2021), {{sys:SYS-REQS-012}} (lifecycle carbon with monetised values). All 21 requirements have verification method and rationale set. Lint returned clean with zero findings; zero orphan requirements.

Next

The next session should begin component-level decomposition of the {{entity:Transport Demand Modelling Subsystem}} — it is the highest-priority subsystem because every other subsystem depends on its outputs (time savings feed economic appraisal, traffic flows feed environmental assessment, turning counts feed microsimulation). Components will include the trip generation module, trip distribution/gravity model, mode choice model, highway assignment engine, and public transport assignment engine. Subsystem requirements, interface definitions, and verification entries will follow.