- Identifies approaching cars from up to 140m away
- integrated tail light
- Easy to install on seatpost
- Seamlessly connects with Garmin and Wahoo cycling computers, as well as Garmin's Varia app (and other cycling apps) for smartphones
- Decent battery life
- A little pricey
- Charges via Micro-USB, not USB-C
I've been doing a fair amount of biking lately, and the one thing I'm always a little concerned about is that some car is going to come up behind me and take me out -- or at least sideswipe me and knock me off the road. The chances of that happening are small where I ride in rural New York, but I've had friends who've gotten hit so when I saw Garmin's rearview radars, the RTL515 ($200), which integrates a tail light, and the stepdown($150, no tail light), I thought I'd give them a shot to see if it made me feel safer -- and make me a safer rider.
I have Garmin's entry-level monochrome, and both the RTL515 and RVR315 seamlessly connect with Garmin's cycling computers, as well Wahoo Elemnt computers and iOS and Android smartphones running the Varia app. Also, Garmin says it integrates with third-party apps such as Ride with GPS to overlay your maps with rearview radar alerts (I did not try that, however).
You get mounting options for three different seatpost types, so it should fit most bikes (each of them mounted vertically to the seatpost of my Giant gravel bike without a hitch). The radar is easy to remove for charging -- it charges via Micro-USB, not USB-C -- but keep in mind that also makes it easy to steal if you leave it on your bike unattended. Battery life for RTL515 is rated at 16 hours with the light in day-flash mode and 6 hours with it in solid mode. The lightless RVR315 offers up to 8 hours of battery life.
When a car is approaching you from behind, it shows up on your computer as a small icon -- essentially a round blip -- on the side of your screen. And it can identify multiple cars approaching and show them on the screen with their appropriate spacing. It can "see" cars up to 153 yards (140 meters) away. With a smaller computer like the Edge 130, you do have to regularly glance down at the screen to see the cars coming. But often I would see them before I heard them, allowing me to move over to the edge of the road to give them more room to pass me.
My brother-in-law is a more serious biker than I am, and I had him try out the RVR315 because he already had a tail light. He was riding on New Jersey roads that had a lot more cars on them. The radar integrated seamlessly with his Wahoo bike computer and he was impressed that it indeed picked up multiple cars as they approached. "Each time I went on a ride with it, I definitely felt safer." His computer showed little car icons; the larger the screen, the easier it is to be alerted.
If you have your phone mounted on your handlebars and are using the Varia app, along with the car graphic you also get a tone and vibration alert. However, a lot of people prefer riding with a dedicated cycling computer rather than a phone.
Some people have mirrors on their helmets to spot cars behind them. A mirror is certainly a good safety feature, but the radar can potentially spot a car coming toward you before you see it in your mirror, so the radar would still be additive. I know people who use both and like the increased ability to see what's coming up from behind them.
Obviously, if you own a tail light already, there's no reason to spend the extra $50 on the RTL515 unless you want an integrated solution. At $200, the RTL515 is a little pricey, but it's a really nice little accessory that does make you feel safer while biking.