Anything which might encourage drivers of motor vehicles to control their exasperation at the antics of their fellows is to be taken seriously. According to a report in Nature for September 2, the habit of switching lanes without necessity is prompted by an illusion. The action arises from the impression reaching the driver that cars in an adjacent lane are travelling faster than his own, something that appears to be anathema to the majority, and productive of hazardous reactions. Estimates of relative speed are false because more time is occupied in being overtaken by other drivers than in overtaking them.
In computer simulations of two lines of traffic with identical characteristics apart from a variation in the gaps in traffic, it appeared that reducing the frequency with which a driver glanced at the adjacent lane from once every second to once every two seconds reduced the impression of a speed difference. Drivers respond to the illusion that the adjacent lane vehicles on a congested road are moving faster than the observer's car even when both lanes are travelling at the same speed because vehicles that are moving fast spread out and those that are moving slowly pack together. Drivers look forwards rather than backwards, so that vehicles which are overtaken are quickly lost to sight whereas those which overtake are conspicuous for longer. Moreover, drivers are more likely to interest themselves in the next lane if they are moving slowly and therefore relatively idle. The illusion takes an added significance as the distance travelled by vehicles increases much faster than the amount of roadway made available.
I am not sure that I should care to try to explain this to a fuming driver labouring under the impression, true or false, that everyone else is travelling faster than himself and therefore denting his precious ego.