FTTI from simulation, not assumption

Client & context

The safety concept for AstaZero's Test Robot — equipment that physically drives autonomous trucks on a closed proving ground — needed defensible Fault Tolerant Time Interval (FTTI) figures for the vehicles under test.

The problem

FTTI is a cornerstone of any ISO 26262 timing argument: how long the system can tolerate a fault before a hazard occurs. Estimating it by engineering judgement leaves the weakest link in an otherwise rigorous safety case — an assessor can challenge every number.

What I did

• Built a simulation tool computing FTTI for vehicles on a closed proving ground.
• Modelled vehicle dynamics and failure-response timing per ISO 26262 — fault occurrence, detection, reaction, and transition to the safe state.
• Used the simulation results directly in the Test Robot safety concept, replacing assumption-based timing budgets with computed evidence.