Auto-Dimming headlamp behaviour

[Rchalk]

I have a 2017 Edge Titanium with auto-dimming HID headlamps.  I have noticed that a lower speeds, the high-beams activate almost immediately after passing an oncoming car, but at higher speeds like 65-70 MPH, it takes almost 4 seconds.  This seems counterintuitive to me, as faster, longer visibility is more important at higher speeds.  What are your thoughts?

[Haz]

From the 2017 Edge Workshop Manual...

 

Automatic High Beams

The automatic high beam system uses an interior rear view mirror mounted camera to monitor surrounding traffic conditions and high beam usage. The camera is hardwired to the IPMA and serviced with the interior rear view mirror assembly. The IPMA communicates light information over the HS-CAN2 to the GWM then the GWM sends the information to the BCM over the HS-CAN1 .

 

The automatic high beam feature is active only when the headlamp switch is in the AUTOLAMPS position.

 

During nighttime driving, the automatic high beam system automatically turns the high beams on if it is dark enough and no other traffic is present. When the system detects an approaching vehicle's headlamps or a preceding vehicle's rear lamps, the system turns off the high beams. When the approaching vehicle's headlamps or the preceding vehicle's rear lamps are no longer detected, the high beams automatically turn back on.

 

 

Light levels measured by Image Processing Module A (IPMA) determine the Auto High Beams' on-or-off status, without any consideration of vehicle speed.

 

As you look back on your low-speed versus high-speed experiences, might there have been differences in the presence of street lighting or adjacent-to-road lighting which may be inhibiting the IPMA from actuating high beams more quickly?

 

Good luck!

 

[Rchalk]

Thank you for the detailed explanation.  However, the situation I describe is not a function of ambient lighting.  I live in a rural area, with winding, 2-lane roads, and on those I experience almost instant high-beams when I meet an oncoming vehicle.  The high-speed response is on a 4-lane divided highway, with very little traffic in the evening, so many times it is completely dark.  I am well aware of the effects of lighted signs, etc., that may mimic headlights or taillights.

 

Thinking about this, I will have to check if it is affected by traffic behind me.  I suppose a small amount of light could be reflected by the inside of the windshield, and find its way back to the camera in the mirror.

 

thanks again.