Adaptive Cruise Control (ACC) can work in rain, but its performance, accuracy, and safety can be affected depending on the type of sensors used and the intensity of the rain.

Below is a detailed explanation of how rain impacts ACC, why problems occur, and when it is safe or unsafe to use it.

Is Adaptive Cruise Control Good in Rain?

Adaptive Cruise Control uses sensors to maintain a set speed and automatically adjust distance from the vehicle ahead.
These sensors include:

Radar sensors (most common)
Camera-based systems
Lidar sensors (in advanced cars)

Rain influences each of these differently.

1. How Rain Affects ACC Sensors

A) Effect on Radar Sensors

Radar is relatively resistant to rain, but heavy rain can cause:

Signal scattering
Reduced detection range
Inaccurate distance measurement
False detection or missed detection

Light rain: ACC usually works normally.
Moderate rain: Range decreases but still functional.
Heavy rain: ACC may warn the driver, reduce functionality, or switch off automatically.

B) Effect on Camera-Based ACC

Cameras are more sensitive to rain than radar.

Problems include:

Water droplets obstructing the lens
Poor visibility
Difficulty detecting lane markings
Inability to identify vehicles or brake lights

If the camera cannot “see,” the ACC will fail or disengage.

C) Effect on Lidar Sensors

Lidar uses light pulses. Rain can:

Scatter beams
Create noise
Reduce accuracy

Lidar struggles the most in heavy rain.

2. Vehicle Warnings and Safety Limitations

Most modern vehicles include safety notifications such as:

“ACC temporarily unavailable”
“Front sensor blocked—clean sensor”
“Reduced visibility: ACC performance limited”

These warnings usually appear when rain is too heavy for reliable sensor operation.

3. Is It Safe to Use ACC in Rain?

ACC is safe to use in:

Light rain
Short showers
Wet roads with clear visibility
When sensors are clean and unobstructed

ACC is NOT recommended in:

Heavy rain
Storm conditions
Fog combined with rain
When hydroplaning risk is high
When visibility is severely reduced

During such conditions, the system may misjudge distances or fail to detect obstacles.

4. Why ACC May Perform Poorly in Rain

Sensors get covered with water or dirt
Visibility is reduced
Road reflections confuse cameras
Detection range becomes shorter
Hydroplaning changes stopping distance
Wipers may not fully clear sensor areas
Splash from other vehicles blocks view

5. How Automakers Improve ACC for Rain

Modern vehicles use technologies like:

Heated radar sensors to minimize moisture
Hydrophobic camera lens coatings
Advanced filtering algorithms
Sensor fusion (radar + camera + lidar)
Rain-level detection to adjust ACC sensitivity

These features improve performance but do not eliminate all weather limitations.

6. Best Practices for Using ACC in Rain

✔ Reduce set speed

Helps compensate for longer braking distance.

✔ Increase following distance

More time to react if the system fails.

✔ Ensure sensors are clean

Before driving, wipe radar and camera areas.

✔ Stay alert and keep hands on wheel

ACC is not a substitute for driver attention.

✔ Be prepared for sudden ACC disengagement

Heavy rain may cause the system to shut off.

Conclusion

Adaptive Cruise Control can work in rain, especially light or moderate rain, but its performance decreases as rain intensity increases. Heavy or stormy conditions can cause inaccurate sensing or system shutdown.
Therefore, while ACC is helpful, drivers must remain attentive and use manual control when conditions become unsafe.