Home > Human Factors history and studies > Nagoya Experiment – drivers are bad followers

Nagoya Experiment – drivers are bad followers

When we are asked to follow another car at a constant speed we tend to make little variations in speed rather than driving at a constant speed. Those variations can initiate brake reactions in drivers following us, and then drivers following them – a wavelike proceed of the brake reaction that can initate a traffic jam for no reason. Mathematical this behaviour is can be described similar to a damper, two waves influencing a third wave. One wave describes the acceleration/deceleration of the lead driver, another wave the acceleration / deceleration of the following driver, those both waves influence the acceleration / deceleration of the traffic behind those cars (described by the third wave). How easy and fast, within a couple of seconds, that can happen you can see in the video below. The study behind the video was conducted by Prof. Sugiyama from Nagoya university. Drivers were asked to drive in a roundabout with constant speed, following other drivers. There occur traffic jams for no reason after a couple of seconds.

Connected car technology might be able to limit the proceeding of traffic jam shockwaves such as in the video by informing drivers about variations in traffic seconds before the drivers notices a behaviour change in their lead cars (e.g. Fuchs et al.). Such system feedback might be “too late” to help drivers driving directly behind the lead vehicle as the lead car’s system needs time to recognise and communicate the braking event to the other cars, but it could help the driver behind that car. Another variable to consider is how drivers react to such a system feedback, if the system feedback could / should include guidance for the response – e.g. recommending the driver to decrease to a certain speed to keep in flow to avoid too harsh braking. Harsh braking might result in the next shockwave and should be avoided. Research in car-following behavior is not new, e.g. Ranney discusses car-following models in his paper from 1999 or by Panwai et al. in 2005, rather “rediscovered” in course of higher automated vehicles and connected cars.

Another interesting aspect is the personal distance that a driver prefers and keeps to other cars for hisher feeling of safety. It is something indivdual, depending, e.g. on personality and driving style. However, in dense traffic drivers maybe forced to keep smaller distances. The driver needs to satisfice between the safety levels that the he/she wants to keep and getting with the traffic, e.g. if the traffic density is high and the driver would keep a longer safety distance to the car in front this longer gap could be used by other drivers to move in. IF the safety distance is reduced, does this then influence how drivers react to braking of a lead vehicles? How would they react if the system provides a suggestion for a certain speed, would they follow the suggestion?

Source:
New Scientist

Fuchs et al.

Ranney
Panwei and Dia

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