Volvo 2008 S40 Owner's Manual page 148

BLIS does not function in sharp curves.
BLIS does not function when your vehicle is backing up.
If you are towing a wide trailer, this may prevent the BLIS cameras from detecting other vehicles in adjacent
lanes.
How BLIS functions in daylight and darkness
Daylight
BLIS reacts to the shape of surrounding vehicles. The system is designed to help detect motor vehicles such as cars,
trucks, buses, motorcycles, etc.
Darkness
BLIS reacts to the headlights of surrounding vehicles. In order to be detected by BLIS, a vehicle in the blind area
must have its headlights on. This means, for example, that the system will not detect a trailer without headlights that is
being towed behind a car or truck.
WARNING
BLIS does not react to cyclists or mopeds.
BLIS does not react to vehicles that are standing still.
The function of the BLIS cameras may be affected by intense light, or when driving at night in areas where there
are no external sources of light (e.g., street lights, other vehicles, etc.). In such cases, the system may react as if the
cameras were obscured.
In both of the above mentioned conditions, a message will appear in the information display.
When driving in such conditions, the system's function will be limited or it may be temporarily switched off. See
page 161 for instructions.
When the message is no longer displayed, BLIS will return to normal function.
The BLIS cameras have the same limitation as the human eye. In other words, their "vision is impaired" by
adverse weather conditions such as heavy snowfall, dense fog, etc.
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06 Starting and driving
Blind Spot Information System (BLIS)-option
Limitations
In certain situations, the BLIS indicator light(s) may illuminate even when there are no other vehicles in the area
monitored by the system.
NOTE
If the BLIS indicator lights illuminate occasionally even when there are no other vehicles in the blind area, this does
not indicate a fault in the system.
In the event of a fault,
The following are several examples of situations in which the BLIS indicator light(s) may illuminate even when there
are no other vehicles in the area monitored by the system.
Blind spot syst. service required will be displayed.