Garmin Varia RearVue 820 Radar Taillight

A cycling radar tail light built for road riders who train in traffic, the Garmin Varia RearVue 820 tracks approaching vehicles up to 175 meters out and delivers that data to a paired Garmin head unit or smartphone before most riders can hear an engine. That lead time is the product's core value: instead of reacting to sound, the rider sees threat level, speed differential, and vehicle count on their display, with enough warning to hold a line or check a shoulder before the vehicle is within striking distance.

The radar sweeps a 60-degree beam within a 220-degree field of view, classifying vehicles by size and flagging those traveling at the same speed as a distinct alert — the scenario where judging a passing gap becomes unreliable. The tail light outputs up to 100 lumens in Day Flash mode with visibility to 2 km (1.24 miles), and a built-in brake light reads deceleration in real time, changing its flash pattern to signal trailing traffic when the rider is slowing or stopping. Battery life scales with mode: 24 hours in Day Flash, 15 hours in Peloton mode, 10 hours in Solid or Night Flash, and 30 hours with the light off and radar running.

At 90 grams and 98.9 x 25.9 x 43.2 mm, the RearVue 820 mounts to round, aero, and D-shaped seatposts via a quarter-turn mechanism and connects to compatible head units and smartphones over ANT+ and Bluetooth Low Energy. The IPX7 water resistance rating covers submersion to 1 meter for 30 minutes, placing it above any realistic on-road weather condition and a clear step above the splash resistance typical of tail lights in a lower price bracket.