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    • So what’s the big deal? There are plenty of safety accessories like flashing tail lights and high visibility apparel on the market. They work by making it easier for drivers to spot you on the road, but do nothing to let you know there is a car behind.

      Sure, you can buy a rear mirror and mount in on yourhelmet. But they don’t work well for triathlon and TT training, where you ride with your head low.

      What about a rearview camera with a small screen on the handlebars? That sounds complicated. I’m not aware of any wireless options lasting over few hours. Besides, could you even tell there is a car 140 meters behind hidden under the shadow of a tree? That is why I like the simplicity of a radar solution.

    • Here is how the radar works:

      When Garmin RTL 510 is paired to a Garmin bike computer (in my case its with Garmin Edge 1030) a small icon appears in the upper right corner of the screen. It is visible in every mode. This way a car can’t sneak up on you while you change settings.

      When the radar detects a car approaching (only from behind) it displays a small strip on the right or left side of the screen (configurable). The strip shows each car as a dot moving closer to a stationary dot at the top of the screen, which represents you. 

      Depending on how fast the car is approaching relatively to your current speed the sides of the screen show a slight orange or red glow. It is very subtle, but effective. Orange for incoming. Red - incoming fast!

      Once the last car passes, the radar takes a second to confirm that there aren’t any more cars and glows green. The road is clear so the strip with dots disappear. As soon as it detects another incoming car, the strip with dots shows up again and the process repeats.

      What about audible alerts of incoming cars? Yes, there are 2 styles of alerts: single-beep and multi-beep. On busy roads I turn off audible alerts, but on rural roads I turn on multi-beep, which is nice and loud.

    • How accurate is this radar detection system?

      I tested it on a busy stretch of the coast highway, riding from Santa Cruz to Pescadero in California, and back. Over a 70 mile, 3.5 hour ride it didn’t miss a single car.

    • The route is a part of the Ironman 70.3 Santa Cruz race course. It is a fast 55 mph (88 km/h) divided highway, with most cars cruising at speeds of 65 mph (105 km/h) or faster. The ride on Highway 1 is unnerving. Imagine being stuck in a wind tunnel going North and setting a world speed record going South. All that plus cars. 

    • The radar did show a few “ghost” cars that never materialized, but there could be many reasons for it. When going around a turn, a car behind you disappears field of view behind the bend only to reappear again on a straightaway. The radar can only see what you can see.

      In other cases a car behind turns into an intersecting road or into a parking lot. They are no longer a threat and thus off the radar. 

      There was one time when the radar showed 2 dots instead of 3. Turns out there was a car drafting behind an RV and it was completely invisible until the last few seconds, when it turned into 3 dots. If I looked back I wouldn’t have seen that car anyway. 

    • If you are sold on the concept here is what you are getting in the box:

      - Garmin Varia RTL 510

      - Quarter turn mount and a rubber adapter for a round or aero seat post.

      - Two micro-USB sync & charging cables.

    • I hacked together a semi-permanent and much more secure mount by using a spare K-Edge Garmin handlebar mount. It also makes it look more integrated with the bike.

    • How heavy is this flashy anchor?

      Garmin RTL 510 weighs 71 grams. Mounted with an adapter it weighs 105 grams.

    • Is it worth the money?

      For me, yes. Sure $199 is not cheap, but its worth it. I wouldn’t bother to write a review if I wasn’t convinced that this device can save lives. It makes me feel much safer on the road. A warning with a few precious seconds to spare can make a huge difference. There are things in life not worth saving money on, this is definitely one of them.

    • TLDR: I love my Garmin RTL 510

      1. It alerts me of up to 3 cars behind as far as 140 meters - 82 bike length behind. You’ve read that right. I confirmed it on the road.  

      2. It has really bright LED even in daylight. Garmin claims it is visible up to a mile away in daylight. I think it is close to that. 

      3. It lasts between 6-15 hours depending on the mode. When connected to Garmin computer it alerts me if the battery is low.

      4. It is plug-n-play setup if you already own a Garmin computer and it is fully integrated at the software level. When active, the radar is visible on all screens (even in settings) and hides away when there are no cars around.

      5. It beeps, flashes and shows me dots for each car. How fast those cars are coming and how far they are behind. 

      If you have this radar system, I’d love to hear from you with your experience. If I missed anything and you have more questions, please ask them here. 

      Ride on and be safe out there.

    • I share your concern for sharing the highway with high speed vehicles ( only a few of them are cars in my neighborhood, many are large trucks where I ride somedays - dump trucks, 18 wheelers, flat bed trucks etc ) and most of them are courteous and move into the other lane, but every now and then, they don't move all the way into the other lane and force me to move onto the shoulder to feel safer, which may or may not be smooth, or even paved. While most are courteous, as you and I both know, it only takes one, who is not, to leave you with a very bad day; so I am very interested in the RTL 510. I have been looking for one of the very bright red LED taillights I see riders sporting these days.

      Unfortunately, the cost for this system is not $199, because you also need a Garmin bicycle computer which seems to run ~$400-$800 bucks or so.

      But I did find a Garmin RTL 510 tail light bundle on Amazon for $299 which includes the very same RTL 510 radar taillight AND a coordinated display for the handlebars which shows the vertical display of your Garmin bike computer. I am happy with my current bike computer, and a Garmin GPS 520 would be a nice upgrade, but I ride more than just one bicycle so..... I think I will order the RTL 510 system for my bike.

      Great review, thanks so much. 🙂

    • But I did find a Garmin RTL 510 tail light bundle on Amazon for $299 which includes the very same RTL 510 radar taillight AND a coordinated display for the handlebars which shows the vertical display of your Garmin bike computer. I am happy with my current bike computer, and a Garmin GPS 520 would be a nice upgrade, but I ride more than just one bicycle so..... I think I will order the RTL 510 system for my bike.

      I'm so "locked in" to the Garmin eco-system that I failed to consider other head units like Wahoo. Thank you so much for contributing and doing further research for non-Garmin options!

    • I bought this today because I tend to trust Amazon itself, and I have never had an issue with returning something that was not as I expected or wanted or whatever. Interestingly, I could not find this item with the pictured Garmin display on the Garmin website even after looking around for at least 15 minutes, so I have some concerns - but it should be here tomorrow or Sunday, so I'll report back my opinion when I see it.

      As far as I can tell, the Garmin RTL 510 taillight does not integrate with the Wahoo head units , but that's a WAG based on looking at Wahoo's website, not a confirmed known fact for me.

      On the Amazon image I posted, it looks like the display is a Garmin display that ONLY displays the radar display seen on the Edge head units. Again, I will know more by tomorrow.

    • I’ve often thought about buying this but never have because I have wondered what it would be like on the busy roads I ride on. Does it get distracting? Do you think it makes you ride safer/at the end of the day, aren’t we usually riding as far over to the right as possible?

    • Good find. I'll probably buy that bundle too, depending on what you find out. I've been hit 4 times on my bike, most recently yesterday. 3 were harmless but one sent me in a heli to Stanford emergency with a fractured skull that the docs said most people would not have survived.

      My concern is this only tells me that they are coming for me, which I already know. What I want to know is are they going to hit me — should I veer into the ditch? I knew the guy yesterday was approaching from behind, I just didn't know he was going to sideswipe and send me to off the road.

    • On busy roads I would recommend turning off audio alerts. It doesn’t get visually distracting, but excessive beeping definitely gets you.

      There are many roads where the right shoulder is too narrow or non-existent. Those stretches are particularly stressful. You can’t really turn your head back too much or else there could be something on the road. The radar gives you that reassurance, so you don’t need to look back as much.

    • I received my Garmin RTL 510 bundle package this morning from Amazon, and it does, indeed, contain both a radar tail light, and the displayed wireless handle bar display that shows the radar signal movement as seen on the Edge head units.

      Here is a picture of my box I received this morning, and there are 2 devices - tailight and display within it. I did open it and check.

      I haven't even mounted it yet. Way Cool!!

    • I mounted my units this morning, and like you, I think, I have some reservations about the mounts. I may have to look into aquiring a mount like you did, if I can purchase one sperately somewhere.

      The rubber band mounts are easy to attach - or to remove, as well - and I worry a bit about long term durability, and general security, from brigands, and vibration and gravity. The "rubber bands" are really high strength Ethylene Propylene Diene Monomer bands, only available from Garmin, but still.... Not as secure as real bolts and screws, but perhaps cheaper, and certainly, easier to attach quickly without tools.

      The light/radar unit mounts are REALLY designed for vertical seat posts - but I have a mountain bike with a small bag on a luggage rack that doesn't offer me a way to use the seat mount post, so I have attached the light/radar unit to one of the 1 cm diameter supports of the luggage rack beside the rear wheel, extending up from the rear axle. We'll see how that works in the next few days. I am unwilling to remove the pack from my luggage rack as I am carrying other stuff to use as I travel about.

    • On last night’s ride I was more conscious about how I might use it and one scenario is looking over my shoulder for cars before merging across lanes. I never feel 100% confident about that.

      The scenario is i’m In the bike lane of a 4-lane road (two in each direction) when I want to cross over 2 lanes to get to a left turn lane. I look over my shoulder but my dark glasses obscure the view a bit but especially my forward riding position limits my view. I always fear I miss seeing an aggressive driver coming in hot.

      Does this detect cars two lanes over?

    • I finally got to go riding today after a couple days of rain. My RTL 510 radar tailight bundle worked flawlessly.

      I was a bit concerned as I mounted it on the right side of my rear wheel on a luggage pannier support, whether that might compromise its sensivity or accuracy. It also tended to not be exactly vertical, but slanting downward maybe 10 or 15 degrees from vertical. If I had mounted it on the left side of the wheel, it would have been pretty close to the deraileur and the drive gears.

      Despite these concerns, it worked flawlessly, detecting cars before I could see them in my rear view mirror, and rendering them on my display until they passed me on my left. The display was very bright and easy to see and interpret in bright sunlight. Cars were detected at least 200 yards or more behind me.

      The head unit is smart too - it does not render or display cars that have passed me in the opposing lane and are driving away from me, NOR does it render vehicles crossing the road behind me at distances where it clearly sees cars approaching me. In other words, the display is "smart" and ONLY displays car/vehicles approaching me from behind me. So I don't have to interpret other false positives, Cool!

      Chris asked if it will detect vehicles two lanes over behind me as they approach on a 4 lane highway - while I did not actually evaluate this, the device was so sensitive and so precise, I am pretty certain it will detect cars two lanes to your left as you ride in the shoulder of the road. It certainly renders cars until they actually depart in front of you, so it sees them when they are directly beside you.

      I also had some concerns with the security of the mounts, but over a 30 mile ride today, they seemed to work flawlessly also. So good news all around!

      Go Garmin!! 👍🏻

    • Turns out Garmin actually makes a dedicated round post mounts that used to be included with the previous generation of the radar. Now it is sold separately.

      Garmin Seat-post Quarter Turn Mount For Varia is $20 well spent on a high quality mount vs using included rubber bands.