Fitting Childseat To Bicycle Increases Overtaking Distances By Motorists (No Child Required), Finds Study

A new study has found that those cyclists who ride with childseats attached to the rear of their bicycles are given more room by motorists. Ditto for towing child-carrying trailers.

The Belgian-lead study has been published in the latest issue of Transportation Research. Researchers—using dummies rather than real children—examined whether motorists identify and classify the cyclists they see ahead of them.

In many collisions, motorists claim they were not aware of the cyclists they hit. Two-wheelers have an acronym for this supposed inattention from motorists: SMIDSY, “sorry, mate, I didn’t see you.”

This new study, like a number of similar previous ones, appears to show that motorists can often see cyclists perfectly well, but that some cyclists are overtaken more closely than others, suggesting that some motorists—either consciously or unconsciously—give more space to those cyclists they deem to be more worthy of protection.

“Drivers of motorized vehicles adapt their overtaking manoeuvre when they overtake cyclists transporting a child, keeping greater and therefore safer lateral clearance distances,” concludes the latest study, conducted by, among others, Toon Ampe of Vrije University in Brussels.

One of the study’s co-authors is British psychologist Ian Walker who has been studying “close pass” overtakes of cyclists for many years. His much-cited 2007 study found that bare-headed women cyclists were afforded greater passing distances by motorists than helmet-wearing male cyclists. That study, like the new one, used bicycles equipped with cameras to measure passing distances.

In his 2007 study Dr. Walker recorded data from 2,500 drivers who passed him on the roads close to his workplace, the University of Bath. Half of the time he wore a bicycle helmet and half of the time he didn’t. The results showed motorists tended to pass him more closely when he rode wearing a helmet. 

Furthermore, he found that the greatest overtaking distance was given when he sported a long brunette wig to fool motorists into thinking he was a bare-headed female cyclist.

“Wearing a bicycle helmet led to [motor] traffic getting significantly closer when overtaking,” concluded Dr. Walker at the time. Along with an Australian statistician he replicated the study in 2018 with similar findings.

The new study adds the fact that motorists appear to be able to identify child-carrying devices fitted to bicycles, and they modify their behavior when approaching cyclists so equipped.

(No child is required to be sitting in the child seat or trailer for the application of the safety benefit—many cyclists have anecdotally reported that they receive wider overtakes even after dropping their children at daycare or similar.)

“[The study] feeds into the evidence that overtakes [of cyclists by motorists] must be, to some degree, the product of thought,” Dr. Walker told me by email.

“It might be unconscious or not, but predictably across several studies, changing the rider’s appearance alters behavior by motorists.”