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Tesla·Machine Learning Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Tesla ML engineer screen, one coding problem focused on physics-based safety logic. Pretty niche for an ML role but I guess autonomous driving means you need to think in real-world units, not just tensors.

Questions Asked (1)

Q1

Write a function in Python that decides whether a vehicle should brake immediately, given current speed, distance to obstacle, maximum deceleration, and reaction time. Return the braking decision, when braking starts, and the expected stopping distance.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

The physics tripped me up more than the code did.

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AI HintsAI Generated

Suggested Approach

Clarify the physics model first: constant deceleration after a reaction time delay. Then derive the stopping distance formula and implement a function that returns a tuple with the decision, braking start time, and stopping distance, handling edge cases like zero speed or negative values.

Pro tip: Mention that in real autonomous driving, sensor latency and actuator delays are critical, so the reaction time parameter should be configurable and validated. Also, consider using SI units consistently and document assumptions.

1. Clarify requirements and assumptions

Ask about units, whether deceleration is constant, and if the obstacle is stationary. Confirm that reaction time is the delay before braking starts.

2. Derive the stopping distance formula

Compute distance traveled during reaction time (speed * reaction_time) and braking distance (speed^2 / (2 * max_deceleration)). Sum them for total stopping distance.

3. Implement the function

Write a Python function that takes speed, distance_to_obstacle, max_deceleration, and reaction_time. Return a tuple: (should_brake, braking_start_time, stopping_distance).

4. Handle edge cases and validation

Check for non-positive speed, negative inputs, or zero deceleration. If speed is zero, no braking needed. If deceleration is zero, cannot stop.

5. Test and discuss trade-offs

Provide test cases (e.g., just enough distance, too close). Discuss real-world factors like sensor noise, varying deceleration, and safety margins.

Key Points to Mention

  • Physics of stopping distance: reaction distance + braking distance
  • Formula: stopping_distance = speed * reaction_time + (speed^2) / (2 * max_deceleration)
  • Decision logic: brake if stopping_distance >= distance_to_obstacle
  • Braking start time: reaction_time (assuming immediate decision)
  • Edge cases: zero speed, negative inputs, zero deceleration
  • Real-world considerations: sensor latency, actuator delays, safety margins

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.