This Bike Gadget Is Like Having Eyes on the Back of My Head

I’ve been a dedicated road cyclist for years, racking up some 63,000 miles according to my Strava app. Like many cyclists, I sometimes suspect I got into it as much for the gear as anything else. (Running, try as it might, doesn’t have much mercantilist joy to offer beyond the shoes, which is both a virtue and a pity). Garmin’s Varia RTL515 has turned out to be my favorite, and most useful, piece of kit, keeping me safe as I ride in any sort of traffic.

I noticed with interest Garmin’s 2015 release of its Varia, a radar-equipped taillight that came after it acquired a company called iKubu that had run a crowdfunding campaign for a product called Backtracker. The idea was simple: The light would detect vehicles approaching from the rear, and warn the cyclist via their bike computer or a similar device.

But I balked. It cost $200, which seemed a lot for illumination that could be had at a fraction of the price (and I was still trying to pay off $2,000 wheels). The whole radar-warning thing seemed superfluous, as I prided myself on my ability to detect traffic out of my peripheral vision. I no more needed a Varia than I needed one of those little helmet-mounted rearview mirrors, the sort that make you look like a dentist. Plus, I lived in New York City—there was always something coming up from behind. The thing, I reasoned, would drive me nuts.

When I moved to New Jersey a few years ago, and began riding most mornings with a regular group, I noticed that almost everyone had the Varia, with its long ovular profile, blinking away on their seatposts. I soon began to see why. Unlike my previous riding staple, New York’s State Highway 9 with its massive shoulder, many New Jersey roads seemed to have little to no space to ride beyond the painted edgeline. The sound of cars, meanwhile, was often drowned out by wind or the road noise of other traffic. The increasing prevalence of electric cars means you sometimes don’t hear them at all.

And so I snapped up the third-generation Varia RTL515 and almost instantly wondered why I’d waited so long. No more constant head checks, no being spooked by “phantom” cars. As I ride, the Varia will detect—at a range, says Garmin, of up to 153 yards—a car (or cars, up to 8) approaching from behind. It issues warnings to my cycling computer, a handlebar-mounted Hammerhead Karoo 2, via Bluetooth. The screen depicts a small automobile icon moving along a “car track sidebar,” which is yellow or red depending on the speed of the approaching vehicle. It also communicates with Garmin watches, phone apps and other devices.

One hesitation had been false positives, but I’ve found the Garmin to be virtually error-free in calling out cars. It will warn of a bike, too, which is also useful. And a nice twist is that the light will also get brighter, and flash faster, as a car gets close, providing a visual heads-up to the driver.

I now feel virtually naked without the Varia. On a recent cycling trip to Japan, it was one of the first things I packed. A 4-inch sensor isn’t going to magically protect you from getting struck from behind, and I wish more cars had radar to warn their waywardly attentive drivers of upcoming cyclists. But when your pastime involves operating within a few feet of tons of heavy machinery, more knowledge feels like power.