Does Hi-Viz Really Make No Difference?

One of the longest-running debates in cycling is about high-viz clothing.  Ultimately it’s your choice what you wear when you go out cycling and you probably make an educated decision based on the type of roads you are cycling on, the weather, and lighting conditions.

The debate is often polarised though with some advocating as much high-viz as possible and others saying they don’t want to look like construction workers or bin-men.  There have been some studies in the past that seem to indicate that high-viz isn’t as effective a solution as most would naturally assume and this week a new one was published.

The new study from the University of Bath says that ‘there is little a rider can do, by altering their outfit or donning a high-visibility jacket, to prevent the most dangerous overtakes from happening’.  This very narrow focus on overtaking clearances has already been reported as showing ‘you’re not safer if you wear high-vis in the daytime’ which is clearly not what is being said.  We delved a little deeper into the report to see what they actually found.

Firstly, whilst the study tries to eliminate as many variables as possible by limiting the study to one route with one rider and at similar times of day (which also limits the scope of the study), it really only tells us the reactions of drivers to different clothing choices of one rider on one route. This doesn’t really allow us to make generalisations about drivers elsewhere, despite having a high number of overtakes recorded (>5,000).

The authors have acknowledged that the rider might have behaved differently when wearing different outfits because he anticipated different reactions or felt more vulnerable, but they argue that he attempted to ride the same each day. Commuting times were staggered to avoid the same motorists with the argument that you want to test the reactions of as many motorists as possible, not just the ones that travel along the same road every day at the same time.  The average cycling speed was measured at 12.4mph on the flat, not exactly rapid but not very slow either and not indicative of a novice.  As long as the speeds were held constant for each type of clothing then bias would be removed from the experiment.


The study found that 1-2% of drivers passed less than 50cm away from the rider, regardless of what he was wearing, however, when it came to those who passed less than 75cm away from the rider, there were observed differences. For example, for three of the outfits (‘Novice’ ‘High Viz’ and ‘Police’), only 4-6% of drivers passed less than 75cm away from the rider, compared to 8-9% for the ‘Racer’, ‘Commuter’ and ‘Polite’ outfits (with 2 out of 3 of these not involving high visibility and the other one could potentially have an antagonistic message).  A passing distance of between 50 and 75 cm is actually quite close, especially at speed and is far outside the bounds of normal behaviour (fewer than 1 in 10 drivers pass this close).  Defining ‘dangerous’ as less than 50cm rather than less than 75cm completely changes the outcome of the research.

As the study was based on previous research which found that drivers passed closer to those wearing a helmet or taking the lane (thought to be because these riders were thought to be more experienced), the hypothesis was that certain types of clothing would make the rider look more experienced and therefore drivers might pass closer. This didn’t occur which means that at worst, the use of high-viz has no effect on a tiny minority of motorist who overtake far too close.  This seems to suggest that no matter what you do as a cyclist, there are always going to be idiots in cars who pose a danger – something just about all cyclists would attest to!

Although the results at close passing distances (50-75cm) are encouraging it is a shame that high-vis doesn’t ‘work’ in all situations.  Be thankful then that crashes involving a pedal cycle casualty where the drivers was adjudged by an attending police officer as, ‘Passing too close to a cyclist’ are only 9% of all incidents.  By far the biggest reason for crashes happening is ‘failed to look properly’, something that all humans are guilty of – driver or cyclist.  Wearing bright clothing isn’t just to stop drivers passing too close, it’s about being seen in the first place.  With the majority of cyclist-involved-collisions taking place at junctions it’s here where we need to stand out as much as possible – especially in gloomy conditions.  High-viz is one tool cyclists can use to try to make themselves more visible but nobody would suggest it’s the perfect answer in all circumstances.  Just because it fails to make a difference in some extreme cases doesn’t mean it should be discarded completely.