On a straight, flat, windswept section of US 36 north of Boulder, I see a rider far ahead. At this distance, normally I might be able to make another cyclist, but the blinking red light, with an irregular low-low-bright-low pattern, is unmistakable, even from over a quarter-mile away.
The rider, whoever he or she is, is one of many cyclists these days who use rear and sometimes front lights, even in the daytime. But do these lights work as well as we think? And are the lights alone enough?
In any discussion of cyclist visibility and safety, a victim-blaming undertaking that is partly a cyclist fault he got hit if he did not lit up like a runway at O’Hare — and this should be the case. But the simple, physical fact remains that in any car-bike crash, the rider loses. So involved worth asking: how can we make sure drivers see us? The answer might lie in the way we as humans process visual information.
In a stationary world, two seconds might seem pretty fast — but a car going 30mph will travel at least 55 feet in those two seconds. Ramp the speed up to 50mph, and the car will travel a third of the length of a football field before the driver can even move his foot to the brake pedal. And considered imperative that action happens in those two seconds: a 2016 study in Sweden that measured how drivers pass cyclists on open roads found that most start to steer around the rider roughly 1.5 seconds before the vehicle reaches the rider. The math points to an unsettling conclusion: under normal conditions, if a car is coming at you and the driver tells you, he is not reacting in time to avoid a collision.
Worse, those reaction times are for the undistracted driver. Consider that it takes about four seconds to unlock an iPhone, which at just 30mph equates to almost the entire length of that football field.
Every minute we spend behind the wheel, also processing a few, maybe hundreds, pieces of information: everything from the actions of the car ahead and the angle of the sun. Much of this information is processed subconsciously, and we focus our focus largely on where we expect to see threats. One study that measured gaze behavior and reaction times among drivers at intersections found, no surprise, that drivers directed most of their attention to where they expected other cars to be. And while you might expect intersections to be the most dangerous, a surprising number of riders get hit on straight, continuing roads: about half, according to a 2012 study of 184 riders who were hit.
And while the majority of cyclists in the study attributed the crash to driver inattention, the authors, drawing on other research, underline the common refrain among drivers in these crashes: “I didn’t see him.” That study, and several others, also points out that cyclists tend to overestimate our visibility, in the daytime but especially at night. So part of why drivers see cyclists might be that they’re not looking for them, and part could be that cyclists think they’re more eye-catching than they are.
Overconfidence in our visibility is especially a problem at night when we still see almost as well as we think we do. We have two visual processing systems, explains Dr. Rick Tyrrell, director of the Visual Perception and Performance Lab at Clemson University. We have got a focal vision, which helps us see detail and recognize objects and colors; and a deeper, more primitive system called ambient vision, which helps us move about in our environments and create spatial awareness.
“At night, it doesn’t feel like a challenge to navigate a curve in a car because the ambient visual system doesn’t require much light,” he says, but the focal system is degraded which we don’t often realize until some detail we didn’t notice, like a person on a bike, seems to suddenly materialize in the front of us. Adding to that false sense of security is the fact that the stuff we do see — road signs, lane striping, and other cars— is all engineered to be highly visible at night. The result? Dr. Tyrrell says drivers consistently “overdrive” their headlights, going faster at night than they should.
Fortunately, the human visual system “is exquisitely sensitive to biological motion,” says Tyrrell. He adds that our vision is particularly attuned to identifying humans as humans, based primarily on how they move. Says a skill is engrained that it might be one of the first ones we develop: “research finds that newborns only a few hours old can recognize biological patterns” that help them differentiate people from other objects, he says.
One of Dr. Tyrrell’s research areas is human conspicuity to drivers, especially at night. Conspicuity is slightly different than visibility in that it includes an element of identification; if visibility is seeing something, conspicuity is seeing what something is, which can change how we respond to it. “If a child walks next to the roadway and you fail to recognize it as a child, you can fail to recognize that the object might move in front of you,” Tyrell says. Correctly identifying an object, rather than just noticing it, can mean the difference between a driver simply reacting, and reacting properly.
The two key factors cyclists have some control over when it comes to conspicuity are creating contrast, which helps us stand out from our surroundings; and creating a sense of motion to spur quicker recognition. Research by Dr. Tyrrell and others show that highlighting these areas of motion works best for drawing driver attention, and helps them more quickly identify the motion as human. For cyclists, that means the constantly rotating feet and knees, since our upper bodies stay stationary much of the time.
A 2004 meta-review of studies found drivers consistently recognized fluorescent colors faster, more consistently and from a farther way than standard colors. Fluorescent material reflects a non-visible ultraviolet light in the visible spectrum, making it look about 200 percent brighter in daylight than conventional colors.
No research on which color creates the best contrast, but fluorescent orange is a good pick because it is commonly used on highway safety and construction signs, and orange is rare in the natural environment.
Keep in mind that fluorescents simply work at night when there is no natural sun for the fabric to reflect. Artificial light sources like car headlights and street lamps emit UV light either. At night your fluorescent yellow reflective safety vest is no brighter than anything else in your closet.
At night, your best bet for visibility shifts from bright colors to reflective material, which shines in artificial light. Because reflective can be expensive and often impair the breathability of the garment, it is often important to be selective with placements — which brings us back to biomotion. A 2012 study by Dr. Tyrrell and other researchers found that drivers correctly identified a rider wearing a reflective news 67 percent of the time; the rate jumped to 94 percent when ankle and knee reflectors were added.
Dr. Wood and Tyrrell’s study says address only ankle and knee reflectors but he says that if you have to choose, prioritize the lower-body reflective material. “A jacket has no movement, so a driver could see it as a road sign,” says Trek Product Designer Kurt Heggland. “When you put reflective material in places that move, you become more recognizable.” Also, reflective material higher up on the body may not capture and reflect as brightly from light sources like car headlights, which are directed low.
“One thing to remember is to make sure you have enough reflective material. The reflective piping on lots of garments is simply too small to make a difference,” says Dr. Tyrrell. To create contrast, the material must be large enough to draw attention and pop out of the background. For comparison, the minimum ANSI recommendation for reflective material on the road workers’ apparel is 155 square inches, equivalent to a 10×15 square patch.
And forget your wheels. “Reflective sidewall tires are more effective than clothing in some cases,” says Trek’s Michael Browne. They are distinctly different from other reflective elements that, when riders see them, they instantly recognize them as belonging to a bike.
Because they convey both brightness and a sense of motion, flashing lights work well even during the day. A 2012 study in Denmark found riders with so-called “permanent running lights” had a 19 percent lower “multi-party” crash rate than a control group without running lights.