## 2 Fundamentals and Terminology
### Automotive Lighting System Development Stages
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Gate** & **REQ_01_Lighting_Behavior** & **REQ_02_Fault_Response** & **REQ_03_Response_Time** \\ \hline \multirow{4}{*}{G10} & Define DT validation objectives for lighting: response time, beam compliance, system interaction & Identify fault detection timing and CAN signaling as critical diagnostic objectives & Define maximum acceptable ECU lighting response delay (200 ms) \\ \hline \multirow{4}{*}{G20} & Structure the DT to modularly include lighting elements, sensor emulation, and ECU logic & Include diagnostic logic for LED/sensor fault injection in the DT model & Include timing paths and latency estimators in the DT \\ \hline \multirow{4}{*}{G30} & Test early DT behaviors like auto-on under concept scenarios (e.g., entering a tunnel) & Evaluate error response through simulated fault injection scenarios & Evaluate logic-to-actuator delay through timing simulation in the DT \\ \hline \multirow{4}{*}{G40} & Verify lighting control software in virtual conditions through DT-CAN message simulation & Simulate fault detection logic for various LED/sensor failure cases & Verify latency in signal propagation using SiL \\ \hline \multirow{4}{*}{G50} & Assess real-time lighting system response with DT connected to hardware & Inject real-time faults and confirm ECU detection via HiL interface & Measure actual sensor-to-actuator delay on the HiL bench \\ \hline \multirow{4}{*}{G60} & Link lighting requirements to test cases validated in the DT simulation framework & Trace fault detection events against expected fault model behavior & Document timing conformance with the requirement across configurations \\ \hline \multirow{4}{*}{G70} & Use real measurements to adjust lighting model for beam intensity and distribution & Adjust DT to simulate varying fault severities (LED, power) & Calibrate model delays using real timing logs \\ \hline \multirow{4}{*}{G80} & Simulate real-world events (fog, night driving) to test lighting safety and robustness & Create composite scenarios: LED fault + communication error during fog driving & Inject environmental load (fog, temperature) and measure response time \\ \hline \multirow{4}{*}{G90} & Enable detection of lighting faults (LED failure, delay) via integrated analytics & Enable predictive analytics for fault detection and failure prediction & Predict delay risks using historical timing anomalies \\ \hline \multirow{4}{*}{G100} & Verify DT behavior against lighting compliance regulations (e.g., UNECE) & Confirm diagnostic flow meets regulatory and OEM safety requirements & Validate conformance to latency standards (e.g., ISO), if applicable \\ \hline \multirow{4}{*}{G110} & Automatic lighting validation through DT in CI pipeline post-software updates & Run fault regression tests using CI-integrated DT model & Integrate timing benchmarks into nightly CI validation \\ \hline \multirow{4}{*}{G120} & Monitor headlamp performance live using DT telemetry and support OTA updates & Enable real-time fault status tracking and analytics via cloud telemetry & Enable real-time latency tracking during fleet testing \\ \hline \end{tabular}
\end{table} 
Table 1: Lifecycle validation of a lighting system requirement across DT development gates. form. During integration phases (G40-G50), it enables both virtual (SiL) and real-time (HiL) testing, ensuring that software logic and physical subsystems respond appropriately to various input conditions. From G60 onward, the DT becomes essential for maintaining traceability and realism. It links specifications to concrete test cases, incorporates real-world calibration data, and is capable of executing complex scenario-based tests (e.g., fog, curves, night driving). Advanced features such as predictive diagnostics (G90) and standards compliance simulations (G100) further extend its value.