Home
YOU YUAN

中文

Emergence in lane changing

Every car changes lanes in whatever way is best for itself, and the whole road ends up slower. This was my PhD problem. Right now I'm looking at the lane changes that are rare but have large effects.

TYPE
Traffic flow research
STATUS
Ongoing; the new results are not published yet
WHEN
2016 to now

The problem

A driver changes lanes to get ahead a little. But the gap they move into was the safety distance the car behind had been keeping. That car has to brake, the car behind it brakes too, and the slowdown travels back car by car (fig. 1). One car gains, a line of cars pays for it. When traffic is dense this is happening all over the road, and the road as a whole slows down.

One lane change and the slowdown that travels backBEFOREINTO THE GAPSECONDS LATERslow truckthe car that wants outthe car behind has to brakebunched up, and the slowdown keeps moving backdirection of travel

FIG. 1 · After one lane change

A sketch, not data. The car with the dashed box is the one changing lanes.

Nobody is directing any of this. Each car is only making the choice that is best for itself, and the combined result is bad for everyone. My PhD work was on exactly this: why it happens, and how to correct it.

What I'm doing now

Now I'm looking at the other end of it. The vast majority of lane changes are ordinary; the ones with large effects tend to be the rare few kinds. Rare means scarce in the data, and models don't learn them well. First I want to work out what kinds of rare lane changes there are, and how each kind happens.

Where it stands