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Nudges in a simulated real-life road exit

The road in front of you may look real, and it actually is. Only simulated. This makes it possible to evaluate infrastructure nudges on a real location without actually venturing out into real life.

It is totally possible you will get something of a déjà-vu experience when driving around in this simulator. Only a few trees differ from a real-life location, which is the exact location where this nudge is to be tested in real life later on.

IKA in Aachen built a complete model of the surroundings to be able to make a lot of tests on the real location without actually rebuilding anything or potentially bringing anybody into danger.

And indeed, the simulator assured that none of the 54 test persons were in any danger. Except in danger of being tricked. The participants did not know that they were about to be nudged, as this could have affected the results. Instead, they were told that the test was about distraction, and were given a distracting task to do while driving. Naturally, this task was designed to end just before the nudge appeared. Additionaly, they were also told to go speeding at 100 km/h up until they felt it necessary to slow down in order to stay safe. Such an approch may seem rather odd, but it is because this particular nudge is only active when the driver is speeding, and aims to reduce their speed. Stefan Ladwig from IKA describes the situation.

“We don’t want to slow down drivers who already are driving safely. This is why we will use lamps to nudge them, as lamps can be turned on when somebody is speeding and turned off when somebody is driving safe”.

And in order to get enough data from the simulator study, all drivers were turned into speeders and therefore encountered the nudge. Or actually, they encountered the nudges, in plural. Two different variants of light nudge were used, both based on rows of lights being placed on the roadsides. The first variant simply consisted of every fifth lamp being lit, whereas the second involved the light travelling towards the driver in 50 km/h. This movement is believed to create an illusion of travelling at a higher speed. And it seems to work.

Both nudges reduced the average speeds by a couple of meters per second and made the drivers brake earlier, without having them devote all their attention to the nudge. And just as expected, the moving lights were most effective. The speed reduction is significant, but less than what was expected. Anna-Lena Köhler from IKA explains why this could be.

“The simulator has a wide field of view to all sides, even in the rear mirrors. But it is always fixed to the ground and does not move. Maybe people did not feel that the situation was that dangerous, and did not slow down as much as they would in real life”. But actually,  too large speed decreases may not be good either. “Of course, we do not want people to just hit the brake and stop on the motorway exit. Now the light seems to guide them more safely through the exit,” Anna-Lena Köhler says.

And to make people feel safe and comfortable with the nudge is a top priority. A second part of the simulator study was more focused on driver acceptance. It showcaseed different colours of the lights and made the drivers rate them. Red and orange were found to be the pick. There was initially an idea of having the lights glow red when speeding, and then changing them too a positive green when the drivers reached the desired speed, but this was found to be detrimental. The drivers actually associated the colours with traffic lights, and believed that green lights meant they should speed up again. Quite the contrary to what it actually should mean.

It is not yet known exactly why the nudges work, or if they would work in more complex driving situations, such as having screaming children in a car. Topics like this will be addressed in further studies yet to come. Both that and the studies made provide invaluable input to the development process; input that would have been impossible to get without a simulator. But naturally, it is not only the results from the simulator that count in the end. It is the results from real life. And this light nudge is actually soon to be put up for tria. So soon we will all get to know how it adds up in the real world.