The most likely collision involving a cyclist is being struck by a motorist who is turning into, or out of a junction (Stone & Broughton 2003).
However, collisions from behind from an overtaking motorist are disproportionately more dangerous (McCarthy & Gilbert 1996, Stone & Broughton 2003, Transport of London, 2005). In addition the sense of close passing vehicles is a significant disincentive to cycle (Guthrie, Davies & Gardner 2001, Parkin, Wardman & Page 2007).
Walker (2007) used ultrasonic sensors to measure the distance left by motorists as they overtook cyclists in 2 UK cities. He found less space was left if the cyclist was closer to the centre-line, and if they were wearing a helmet. More space was left if the cyclist looked female (replicated by Florida Dept. of Transport, 2011).
Long vehicles (buses and HGV’s) on average passed closer (Walker 2007, Parkin & Meyer 2010), and caused disproportionately more collisions (Pai 2011).
The average overtake distance increase during the day, with evening peak time overtakes substantially more distant than morning peak time overtakes (Kim et al 2007).
In Australia, the Queensland Transport Market Research found 20% of motorists admitted to not moving over for cyclists. Males, under 30 were the least likely to move over.
The only outfit associated with a significant change in mean passing proximities was the police/video-recording jacket. The 'Polite Notice' top experienced much closer and more aggressive passes. Motorists are responding to the warning that their actions are being recorded, and / or noticing the word 'Police'.
It is reassuring that motorists are able to modulate their behaviour (i.e. close passes are not simply carelessness), but the motives for this modulation is concerning. Assistant Chief Constable Alan Featherstone commented that “video footage is the most successful way of securing a conviction against those who flout the law” (www.PoliceWitness.com).
The only outfit associated with a significant change in mean passing proximities was the Police/ Camera jacket. The ‘Polite Notice’ top experienced closer and more aggressive passes. Contrary to predictions, drivers treated the sports outfit and the ‘novice cyclist’ outfit equivalently, suggesting they do not adjust overtaking proximity as a function of a rider's perceived experience. Notably, whilst some outfits seemed to discourage motorists from passing within 1 metre of the rider, approximately 1-2% of overtakes came within 50 cm no matter what outfit was worn. Even the Police / Camera top lost significance at this distance. This suggests there is little riders can do by altering their appearance, to prevent the very closest overtakes. The researchers suggest that infrastructural, educational or legal measures are more promising for preventing drivers from passing extremely close to bicyclists. The threat of legal comeback (in the Police/Camera vest) was the only thing that made any difference in this study.
Police Witness.com is a UK police endorsed scheme to encourage motorists to protect themselves and their vehicles by the use of personal video.
The Transport Research Lab studied overtaking distances in 1979, and found the average gap to be 179cm. In 2014, Bath University measured 5690 overtakes. They found that for the same area of England as studied in 1979, the average gap had reduced to 113cm. This could be due to busier roads or decreased levels of cycling. The average motorist is less likely to have cycling experience, and therefore less understanding of a cyclists needs.
The same study found that dressing a rider in outfits signalling different levels of experience did not alter the space left by motorists. This included, amongst others, lycra clad “pro’s”, vests with “Novice rider” emblazoned, commuter cyclists, a high viz top with “Police” and “Camera Cyclist”, suggesting the journey was being videoed and a high viz top saying “Polite notice, please slow down”.
'Approximately 1-2% of overtakes came within 50 cm no matter what outfit was worn.'
'Every time I see an adult on a bicycle, I no longer despair for the future of the human race' – H.G. Wells