AV Stopping Distance Calculator

Calculate total AV stopping distance — system latency travel plus braking distance — and the minimum forward detection range your sensor stack must achieve for safe emergency stops.

UDHY Tools / AV Stopping Distance Calculator

⚙️ Input Parameters

Vehicle Speed (km/h)

System Latency (ms)

Full pipeline: sensor→actuator

Deceleration (m/s²)

AV: 4–8 | Emergency: 8–10

Road Friction (μ)

Dry: 0.7 | Wet: 0.45 | Ice: 0.1

📊 Results

🛑

Enter speed, latency, and road conditions to compute minimum stopping distance and required detection range.

Total Stopping Distance

—m

Distance during latency window—

Braking distance—

Friction limit (max safe decel)—

Deceleration status—

Required sensor detection range—

Why Stopping Distance Defines Your Sensor Range Requirement

What This Calculates

Total stopping distance is the sum of two phases: travel at full speed during system latency (sensor capture → inference → planning → CAN bus → actuator), and the physical braking distance limited by tyre-road friction. The result sets your minimum required forward sensor detection range — your LiDAR or camera must reliably detect and classify obstacles at least this far ahead.

When to Use It

Setting minimum LiDAR/camera detection range for your ODD
Evaluating whether latency improvements expand safe operating speed
Checking deceleration doesn’t exceed tyre friction limits
Adverse weather analysis (wet/ice dramatically increases stopping distance)
Regulatory safety case documentation

Formula

v_ms = speed_kmh / 3.6 d_latency = v_ms × (lat_ms/1000) d_brake = v_ms² / (2 × decel) d_total = d_latency + d_brakefriction_limit = μ × 9.81 m/s² Decel must not exceed friction_limit Detection range = d_total × 1.1

Built by Dr. Dilip Kumar Limbu · Co-Founder, MooVita · Former Principal Scientist, A*STAR · UDHY Engineering Tools

FAQs on AV Stopping Distance Calculator

1. How is AV stopping distance different from human driver stopping distance?

The structure is identical — reaction distance plus braking distance — but reaction distance differs significantly. Human reaction time averages 750ms (NHTSA), producing approximately 10m of travel at 50 km/h before braking starts. A well-engineered AV pipeline achieves 100–200ms total latency, producing 1.5–3m of reaction travel at the same speed. However, in novel or ambiguous scenarios, AV latency can exceed human reaction time if perception requires multiple inference passes or confidence thresholds are not met.

2. What is the typical stopping distance for an AV at 50 km/h?

At 50 km/h (13.9 m/s) with 150ms system latency and 6 m/s² deceleration on dry road: latency distance = 13.9 × 0.15 = 2.1m; braking distance = 13.9² / (2 × 6) = 16.1m; total = 18.2m. With 10% safety margin, the sensor stack must reliably detect obstacles at ≥ 20m. At 100 km/h with the same parameters: total ≈ 68.5m — illustrating why high-speed AV deployment requires LiDAR with 100m+ reliable range.

3. How does system latency affect stopping distance?

System latency contributes linearly to stopping distance: every additional millisecond adds (speed_ms × 0.001) metres. At 100 km/h, each 10ms of additional latency adds 0.28m. This is why AV engineers invest heavily in real-time perception — a 50ms improvement in inference time directly reduces minimum required detection range by 1.4m at highway speeds, which is a meaningful safety margin at scale.

4. What road friction coefficient should I use in safety case calculations?

Use the lowest friction coefficient your vehicle may encounter within its ODD. Dry asphalt: μ = 0.7–0.8. Wet asphalt: μ = 0.4–0.55. Wet leaves: μ = 0.3. Packed snow: μ = 0.2–0.3. Ice: μ = 0.05–0.15. If your ODD excludes icy conditions, use wet asphalt as your worst case. The friction coefficient determines maximum safe deceleration (μ × 9.81 m/s²) — specifying higher deceleration than the friction limit is a regulatory red flag.

5. How do I use stopping distance to specify minimum sensor detection range?

Your sensor stack’s minimum reliable detection range must be at least equal to stopping distance plus a safety margin (10–20% is typical). For example, at 80 km/h with 150ms latency, 6 m/s² deceleration on wet road (μ = 0.5), total stopping distance ≈ 46m. With 15% margin, minimum detection range specification = 53m. This number becomes the minimum reliability range in your LiDAR and camera sensor specifications for ODD-relevant targets under all ODD-permitted conditions.

6. What deceleration rate is typical for AV emergency braking?

AV platforms typically limit commanded emergency braking to 6–8 m/s² for passenger safety. The physical maximum on dry asphalt is approximately 8–10 m/s² (approaching tyre friction limit). Sustained deceleration above 0.8g (7.8 m/s²) degrades safety in unrestrained-occupant scenarios. For safety case calculations, always use your vehicle’s verified emergency braking deceleration from physical testing on your ODD’s worst expected surface — not the theoretical maximum.