In relation to multiscale modelling, a category of problem that receives a good amount of attention is understanding how collective (group) movement arises from movement rules defined at the individual level. For example, the direction of each individual’s next move might depend on where that individual’s nearest neighbours are. What type of rules are necessary for the group to stay together? If the group stays together, what does the collective movement look like (directed or meandering)?
Some nice examples are:
What type of individual movement rules are needed to produce a Sheep cyclone?
Bonus question: How close together do the parallel walls (relative to the car width) need to be?