The faster the rider goes, the brighter the Varia UT 800 will be to help watch out for those hazards at higher speeds. When connected with a compatible Edge cycling computer, GPS speed is used to automatically adjust the intensity of the headlight’s beam. At 800 lumens the Varia UT 800 is certainly bright enough at higher speeds for obstacles that may be in the path. To conserve battery life the intensity of the light is lowered at lower speeds.