Is brighter better when it comes to lighting up at night or in low light? And what effect does your light have on other road users? Simon Vincett investigates.
“Thanks for highlighting the need to point lights at the road!” reads one comment on a recent Ride On Lights test. “I live in the CBD but work 20km outside of the city, so my commute goes in the opposite direction to most people. Every second bike coming towards me has high-powered lights pointed straight in my face, leaving me completely blind for a couple of seconds. It’s hard to describe what a disorienting and dangerous experience that is, especially on dark bike paths!”
“I have to disagree,” replies another. “Bright lights are a necessity for all year riding. The see-me only lights are just dangerous. They get lost in the background of car lights and side street lighting. I pass many cyclists here in West Oz on PSPs [shared paths] with their bright lights flashing or steady. I haven’t a problem with them. Just look straight ahead where you’re going and they don’t blind you. I have around 1000 lumens of light on my bike and on unlit streets or poor weather conditions I’m wanting for more. Cars have bright lights so why can’t bicycles?”
There’s wide variation between different riders’ approaches to riding in the dark and their reasons for their practices. The comments above are just two representing the opposing sides of the ‘brighter is better’ debate in bicycling lighting.
Motor vehicle regulations in Australia govern acceptable lighting for car and trucks but not for bicycles, while in Germany the vehicle regulations code (StVZO) covers lighting for bikes. But in the absence of such regulations in Australia, Ride On turns to science.
Someone uniquely placed to judge night-riding best-practice is Professor Joanne Wood from the School of Optometry and Vision Science at the Queensland University of Technology. Wood has led a number of studies investigating how visible bike riders think they are compared to how visible they actually are to other road users.
She says most people fail to take into account the amount of adaption needed in the dark, and what a huge difference this makes to how well you can see at night.
“Generally speaking drivers are not dark adapted, or their level of adaption is not very good, because they are being exposed to on-coming headlights quite a lot more than the cyclists meaning a lot of readjustment for their eyes.
“The cyclists, in comparison, have not been exposed to as much light (headlights) and they are dark adapted to a greater extent, so they can see much better than the car drivers,” Wood says.
It takes minutes for our eyes to adapt between light and dark environments—think of going into a movie theatre out of midday sunlight and how long it takes to be able to see with confidence. Full adaption to that situation takes approximately 30 minutes for a healthy person under 40 years old, though adequate partial adaption comes much faster.
“You [may] think that brighter is better but really it’s better that a cyclist is recognised as a cyclist so that the motorist can give them a wide berth.”
The contrast of light and dark in the road environment at night requires our eyes to cope or adapt to vastly different levels of light in a short space of time. It’s a situation that is neither wholly dark nor completely bright and it pushes the human visual system to its limits.
It’s something Philip Grove, a senior lecturer with the School of Psychology at the University of Queensland, is aware of on both a scientific and personal level as a bike rider.
Grove says in a road user’s visual system there are actually two systems that work in concert: the photopic (cones), which is the system that works in bright daylight and is responsible for colour vision, and the scotopic (rods), which is the system that kicks in at low light levels.
“The glare and the dazzling is a result of being exposed to light that is brighter than what the eyes are adapted to in a given situation. In the city where you have quite a bit of overhead lighting the ambient luminance is sufficient that those bright lights aren’t as dazzling as they might otherwise have been if you were riding on a dark bike path out in the suburbs.”
As a bike commuter himself, Grove is familiar with the issues of bright bike lights and says some things make the effect of bright lights worse, such as mounting them on your helmet.
“The dazzling is worst when the light is shining right in along your line of sight—right into your eyes,” says Grove. “The potential for that to occur from a helmet-mounted light is much greater than from a handlebar-mounted light because the light is free to move around with the riders head. If they happen to be looking you right in the face then they’re going to be shining that light right into your eyes,” he says.
“Now that the technology has come to the point that you can strap a really tiny light to your bicycle that’s quite powerful I think there are going to have to rules about having to aim your lights below the line of sight of on-coming cyclists.”
Another factor is the variation of visual ability between individuals. “It’s definitely the case that people have different abilities to see in the dark,” says Wood. “Some people complain a lot about night time vision and other people don’t. People have different pupil sizes and the size of your pupil determines how much light goes into the eye.”
Ageing brings inevitable decrease in visual ability, even in individuals with 20/20 vision.
“As you get older your pupil size gets smaller,” says Wood, “so you’re going to get less light in the eye. And your capacity to adapt to light and dark gets worse as you get older, particularly over the age of 50. So a lot of differences in ability to see at night are actually more to do with the ageing process as well as people getting eye diseases that affect the way their visual system works.”
While the regulators grapple with changing technology, they should also be thinking about roadways and their use at night.
“Night-time driving is very challenging and the crash risk is higher. While a lot of the technology allows us to see quite well at night we don’t see as well as we think—there’s a tendency for us to over-drive our headlights. We drive too fast and we’re not aware of the fact that there are lots of other things happening on road systems that aren’t bright and we can’t see very well, like vulnerable road users, animals on the road and the like. Realistically we need more time to be able to respond and, therefore, we need to slow down. And that’s true of cyclists as well as drivers.”
Woods says there is a “misperception in the riding community that brighter is better.”
“On the whole you’d have to say that very bright lights aren’t necessary because there’s a certain level of brightness that you need to see because cyclists are dark-adapted anyway from cycling in lower light levels.
“You [may] think that brighter is better but really it’s better that a cyclist is recognised as a cyclist so that the motorist can give them a wide berth. There are lots of bright things in the road environment. We need cyclists and pedestrians to be recognised as vulnerable road users so that the motorists avoid them.”
This concept of being recognised as a bike rider is called perspicuity and it represents a step beyond just being visible. To this end Wood recommends riders wear reflective strips. This is based on experiments of which visibility aids used by bike riders were most effective as reported by car drivers in a controlled situation.
“It’s clearly more important that riders wear reflective strips on the moveable joints of the ankles and knees because that movement pattern is recognisable and we found that it made a huge difference to the distance at which the on-coming drivers could recognise that a cyclist was present. It has to be on a moveable joint because that creates what we call biological motion, which is that signal of human movement so we know it’s a person,” Woods says.
“It doesn’t even have to be very high-grade reflective. We used standard, 5cm wide strips that you can get on a roll and attach to clothes.”
In the meantime as the bike-path arms race continues unregulated, Philip Grove offers a couple of items of advice to deal with blinding lights. “Avert your eyes,” he says. “Don’t look at the light. If you can, change your head height. If necessary, ride on more well-lit roads and paths.”
Illustration by Karl Hilzinger
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