Design a Redundant Railroad Crossing
Company: Zipline
Role: Software Engineer
Category: System Design
Difficulty: medium
Interview Round: Onsite
Design a safe and redundant control system for an at-grade railroad crossing used by road vehicles and pedestrians.
The system should detect approaching trains, warn road users, lower and raise gates, handle failures safely, and support monitoring and maintenance. Discuss requirements, architecture, sensors, actuators, control logic, redundancy, failure handling, and validation.
Quick Answer: This question evaluates competency in safety-critical system design, covering requirements analysis, redundancy and fault-tolerance, sensor and actuator integration, real-time control logic, and monitoring and maintenance considerations.