Despite being available for over a decade, on-bike radar units have only recently gained widespread acceptance by road and gravel cyclists. There are great reasons for riders embracing radar: These devices are lightweight, very effective, and help ease anxiety on rides. I began using a radar taillight late last spring and haven’t ridden on the road without one since.
Radar systems provide you with warnings of vehicles approaching from behind on rides. The taillights on many devices can be set to blink or illuminate brighter when an approaching vehicle is detected, which helps notify drivers of your presence. While a radar does not create a force field or protective bubble around you and your bike, it gives you some time to react and move from the lane.
There are many radar units currently available, and we’ve tested a dozen of them in real-world riding conditions. Some of them work very well, while a few others aren’t worth buying. However, a Garmin Varia is often the radar device our editors grab when they head out for a ride.
Best Overall Radar
Benchmark Radar Light
Radar Camera
Varia Radar Systems
Garmin is the OG of the cycling radar market. And more than ten years after launching the first on-bike radar, Garmin‘s units remain the benchmark against which other brands’ devices are judged.
After acquiring iKubu‘s Backtracker radar concept, Garmin launched the Varia RTL500 in 2015. It updated the Varia to a vertical configuration (RTL510) three years later, and later added Bluetooth connectivity and a mobile application in 2020 (RTL515).
Garmin’s latest radar—the RearVue 820—has quickly become our go-to choice.
When used with a Garmin computer, the new 820 can track vehicle size and location.
In 2022, Garmin introduced a radar taillight with an integrated camera (RCT715). The same year, Cannondale also partnered with Garmin to create the SmartSense system on the Cannondale Synapse endurance road bikes. (SmartSense is also used on some models of the Synapse updated in 2025.)
This year, Garmin introduced the RearVue 820. It’s the company’s biggest refresh to the Varia radar platform in a decade. Along with USB-C charging, improved battery light, and a brighter taillight flash, the highlights of the new 820 are same-speed tracking and vehicle size detection. These are unique features not found on other brands’ radar systems.
Garmin currently offers four Varia cycling radar systems (plus an electric bike-specific device) priced $100 to $400. Each works extremely well, but which device is best for your riding needs and budget?
The Varia RCT715 features a built-in camera,
Varia RTL515
Pros
- Great performance for the price.
- Solid vehicle detection and tracking.
Cons
- Micro-USB changing.
This is our benchmark on-bike radar. Overall, the RTL515 works very well. Weighing only 72 grams, it consistently detects and tracks vehicles up to 140 meters away. While the 515 taillight’s flash isn’t as intense as the Lezyne Radar React or Trek Carback radars, it still offers plenty of visibility—up to 1.6 kilometers—for most rides.
The downsides to the 515 are its lack of USB-C charging and mediocre battery life, which means you get fewer rides per charge than Wahoo’s Trackr Radar.
Buy the Varia RTL515 if…
You’re on a budget but want a proven and dependable cycling radar.
Varia RearVue 820
Released earlier this year, the RearVue 820 is a phenomenal radar unit. Its claimed detection range (175 meters), visibility (2 kilometers), maximum flash (100 lumens), and battery life (15 hours on low) are among the best in the category. At 88 grams, it’s slightly heavier than the RTL515. But unlike that device, the 820 has USB-C charging.
However, it’s the 820’s advanced features that really distinguish it from the 515—and from all other premium radars on the market. Leading the list is same-speed vehicle tracking. Unlike other radar systems, this feature continuously tracks vehicles when they slow down behind you in traffic or to pass on narrow or winding roads. It’s a great feature that you cannot really appreciate until you experience it; then it’s hard to go back.
Two other advanced features are vehicle size detection and lane detection. Again, these are excellent features that are hard to ride without trying. Unfortunately, both features only function with Garmin’s newer x40 and x50-series computers.
Buy the Varia RearVue 820 if…
You want the best radar unit currently available, and cost is not a concern.
Varia RCT715
The 715 is Garmin’s radar taillight with an integrated camera. The 715’s radar functions the same as the RTL515. However, due to the camera, the 715 is double the weight (148 grams) and has a shorter battery life (5 hours on low). Due to the extra weight, the RCT715 also uses a proprietary mount.
At $400, the 715 is a pricey radar. The rear-facing camera is a bonus, particularly when paired with the forward-facing Varia Vue camera light ($550). It’s a great combo for some riders (such as commuters) as it enables them to record and document instances of driver aggression or poor cycling infrastructure.
Buy the Varia RCT715 if…
You need a built-in camera and are ok with added weight and shorter battery life.
Varia RVR315
