Between making ourselves visible and actually being seen there are a number of other factors at play. Understanding the steps in being seen, recognised and reacted to by a car driver can help us think more proactively about how we dress, light up our bikes and position ourselves.
Many of us will be familiar with the phrase SMIDSY – sorry mate, I didn’t see you. The stats are that in 44% of collisions either of the parties did not see the other and in 21% there was a failure to appreciate the speed of the other vehicle.
Making yourself as visible as possible by lighting up your bike like a Christmas tree and wearing bright colours is one thing, but it takes work on the driver’s part to actually ‘see’ you and importantly asses, react and respond to what is being seen. So what is going on for the car driver?
The first step is the driver has to see or perceive that there is something they need to react to. The pool of light from a dipped beam headlight is generally in the 56 to 60m bracket. At 30 mph that distance would be covered in slightly over 4 seconds. At 60 mph it follows that the distance would be covered in 2 seconds. Tests undertaken by Sussex Police (among others) indicate that a person in predominantly dark clothing (a darker shade of grey) will be likely to be perceived at 24-26m while white or bright clothing increases that to 45m. These numbers are important as in that short space of time a lot needs to happen in the brain of the driver.
Reaction time is the space between perceiving the hazard and doing something about it. Most of the studies into reaction time have come up with a real world figure of between 1.5 and 2 seconds, this is used as the basis for crash reconstruction by the Transport Research Laboratory (TRL) and the Institute of Traffic Accident Investigators (ITAI).
What does that mean in terms of distance? For example, a car travelling at 60 mph, the national speed limit which applies on the majority of rural roads, will travel further than the length of a football field in 3.5 seconds.
Using a really quick reaction time, from perception to doing something about it, the car’s travelled 38m of 132 feet. Then it has to slow down or stop.
At 30mph, the predominant limit in urban areas it’s still 66 feet (four and a half car lengths), or almost 20m before the brakes go on and any avoidance is begun. Reading these figures in conjunction with the ones above show how much can happen in the little time which there is for a driver to react.
However visible you are, the driver’s eye sight and brain still has work to do for you to be perceived and seen in limited amount of time. The ‘relaxed’ (or fatigued) focal distance of the human eye is between 11 to 13m. That’s where most of us are looking, most of the time. Looking further requires an actual input. Objects not directly in front of us are also harder to see as visual acuity reduces by up to 70% at only a small deviation away from the central field of vision, which is 5 degrees from the central axis. So part of the perception reaction process is likely to involve rotation of the head, movement of the eye and re-focusing.
That’s quite a lot to happen in the ‘thinking distance’ so anything that we can do to allow us to be seen sooner is going to help. It’s also important to remember that at night, without artificial lighting the visual acuity is reduced to approximately 5% to 10% of the daylight vision.
Be seen, sooner
By making sure we can be spotted from further away, we are giving a driver more time in which to react. White or bright clothing can be seen from nearly twice the distance of black or grey. It is also accepted that movement helps draw attention against other ambient lighting, especially in urban areas, so put lights and reflectors on parts of your bike that move, such as pedals and wheels.
Ensure your clothing and lights allow 360-degree visibility, so you can be seen side on as you cross in front of a side road. Put your rear lights at varying height and make sure they are not obscured by your rucksack or clothing. Think about your road positioning, especially when performing a manoeuvre as objects not directly in front of us are harder to see.
Being highly visible is not the same as being seen, as anyone who has heard the SMIDSY line will know and as we have shown above there are a lot of human factors involved. Even though you are decked out in lights and bright colours from head to toe there is no guarantee that the driver has actually registered you through the flak of other competing distractions upon the driver’s attention: dealing with the inevitable driving tasks (risk situations) and the processing of information from legitimate vehicle systems and their in-car entertainment, navigational devices and mobile phones. To help ourselves stay safe on the roads we need to maintain our own levels of alertness and perception and not make assumptions, especially at junctions, that we have been spotted.