Edge Bike Computer
The device can improve situational awareness. It is not a replacement for cyclist attentiveness and good judgement. Always maintain awareness of your surroundings, and operate the bicycle in a safe manner. Failure to do so could result in property damage, serious injury, or death.
When connected to the Varia™ RearVue 820 radar tail light, your compatible Edge® bike computer shows the vehicle column on the side of the screen when a vehicle is approaching you from behind.
An icon along the side of the screen represents a vehicle behind you. The size of the icon represents the size of the vehicle, as detected by the radar.
The vehicle icon moves up the screen as the vehicle approaches you, representing the vehicle's position relative to you.
The radar calculates a threat level based on vehicle size, speed, and lateral distance from
your path. A 
icon over the vehicle icon indicates that the vehicle is a mid-level
threat. A 
icon over the vehicle icon indicates that the vehicle is a high-level
threat.
When the radar detects a threat, the bike computer emits an audible tone and the screen shows a red or orange overlay on the sides of the screen, depending on the calculated threat level. When all threats are cleared, the bike computer emits another tone and the screen shows a green overlay on the sides of the screen.
You can configure the threat alerts within the Sensors menu on your Edge bike computer (Alert Settings).