Walker, I. (2006). Overtaking bicycles in the UK: Cars versus white light-goods vehicles. PHILICA.COM Observation number 10.
Overtaking bicycles in the UK: Cars versus white light-goods vehicles

Ian Walkerconfirmed userThis person has donated to Philica (Department of Psychology, University of Bath)

Published in transpo.philica.com

Observation
White light-goods vehicles (LGVs) are a common feature of British roads. Although to the best of our knowledge there has been no research on the stereotypical image of “White Van Man”, a key characteristic must be a casual disregard for other road users. If this is true, it would be particularly serious for the more vulnerable classes of road user.

The author rode a bicycle fitted with a highly accurate ultrasonic distance sensor in the UK cities of Salisbury and Bristol in May and June 2006 and recorded over 2,500 instances of motorists overtaking. Here we specifically compare the data from white LGVs to the data from black cars. Black cars were chosen for the comparison because the number of observations in the dataset was almost the same as the number for white LGVs (although this nicety was hardly necessary as the results below barely change if all car colours are combined).

The mean proximity of overtaking black cars was 1.36 m (SD=0.37) whereas the mean proximity of overtaking white LGVs was 1.26 m (SD=0.35). In other words, white LGVs on average passed 10 cm closer to the experimenter’s bicycle than black cars across all the overtaking incidents recorded. This difference is statistically reliable, t(376)=2.69,p=.007 (two-tailed, performed on the square-roots of the overtaking proximities to correct for skew).

The data showed very similar distributions with a simple shift in means between the two groups of vehicles. Whether this shift is the result of personality factors, vehicle factors (systematic difficulty judging width), or social factors is a question for future research. Potential social factors could include a macho subculture, time pressures associated with driving for work, or the relative anonymity provided by a (usually unmarked) white LGV (for a discussion of anonymity and public behaviour see Festinger et al., 1952, and several subsequent decades of social psychological research).

Observation circumstances
This Observation is part of a much larger study being completed at the time of writing which systematically assessed several factors affecting how motorists overtake cyclists. This research was funded by the UK Engineering and Physical Sciences Research Council. The instrumented bicycle was constructed by Jeff Brewster.

References
Festinger, L., Pepitone, A. & Newcombe, T. (1952). Some consequences of deindividuation in a group. Journal of Abnormal and Social Psychology, 47, 382-389.

Information about this Observation
Peer-review ratings as of 09:14:57 on 26th Sep 2017 (from 3 reviews, where a score of 100 is average):
Originality = 226.71, importance = 268.99, overall quality = 251.79

Published on Thursday 15th June, 2006 at 15:49:52.

Creative Commons License
This work is licensed under a Creative Commons Attribution 2.5 License.
The full citation for this Observation is:
Walker, I. (2006). Overtaking bicycles in the UK: Cars versus white light-goods vehicles. PHILICA.COM Observation number 10.

Peer review added 22nd September, 2006 at 08:05:08

A very interesting research. The next what coluor is the sfest one? Maybe safe overtaking is affected by colour or the shape of the bicycle? Nice search for the road police department. What about the colour clothing of the bicycle driver? There is a bit anxiety about the standart deviation (SD). Is it in meters or centimeters? From the statistically point of view the distance is the same with the probability of 90%. But this only a standart deviation. Im actually a physicist, but the subject of the search concerns me anyway. So. it will very interesting to read something about the psychology on the road.

Author comment added 22nd September, 2006 at 08:28:40

To clarify review #1, the standard deviations are in metres, so 0.35 = 35 cm. This is quite a lot of variance, as I think we would expect for a real-world behaviour with many factors influencing it. Nevertheless, the distributions were still sufficiently distinct to reject the null hypothesis that they were drawn from the same overall population, so the effect was quite notable.

Peer review added 19th January, 2007 at 15:26:56

What is the width of a typical white van as opposed to the width of a typical black car?

To overtake the bicycle will require the van or car driver to move closer to the center of the road and hence closer to oncoming traffic. The margin of safety that exists between the overtaking vehicle and the on-coming traffic depends on a number of variables but in general terms the van driver will have a smaller margin than the car driver because vans are wider than cars.

The van driver will be more unwilling to move outwards than the car driver not least because the driver would perceive the danger to themselves of a head-on collision as being more serious than hitting a bike going the same direction!

Martin Nicholson
Daventry UK




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