The Garmin Varia RTL515 is a bicycle radar combined with a rear light. It is the third generation of the Garmin bicycle radars and the only thing the bicycle radar does is see if traffic approaches you from behind. For example, if a car approaches you from behind, you will receive a visual warning with an audible alarm via a cycling computer or a smartphone app.
The scanner can see traffic up to 140 meters behind you and this can be anything from cyclists to cars and from buses to scooters, but also a tram on the tramway next to the bicycle path. In the last thirty meters of an approaching vehicle, the rear light flashes to warn the vehicle additionally.
In the city
In the city, there is virtually no use for such a bicycle radar that warns you about all types of traffic. He is not smart enough to distinguish between cars, scooters or bicycles. You then get too many warnings that are not relevant. Outside the city, on dikes or country roads where you share the road as a cyclist with other traffic, it is very useful and increases your safety.
Especially if you have a road bike, a mountain bike or other sporty bike where you lean forward over the handlebars for streamlining. But in theory you could also mount a mirror, right? But yes, that doesn’t look like much, let alone increase your air resistance.
The question is whether you have 199.99 euros for that. I myself am waiting for a radar to be built into an e-bike as standard. Then I have an ear for it.