"NaSch" means the Nagel-Schreckenberg-model. It's a traffic simulation published by the 2 physicists Kai
Nagel and Michael Schreckenbergin 1992.
It gaves the first explanation for "traffic jam out of nowhere".
The cells represents in the NaSch-model a street of equal sections.
This cells are empty or contains a car with a defined, discrete speed.
The speeds are one of six different values (from 0 upto 135 in steps of
27 km/h). The initial state is given by random. You can define the
density of cars under menu item "options"(15% is default).
A car accelerates, if it has enough empty cells in front and maximum
speed isn't reached. A car slowed, if it has less cells in front.
Additional there is an unmotivated slowing by a part of the cars. The
amount of unmotivating slowing cars is defined by the "dawdle factor",
which you find in options too.
state
representing
0
cell of street without car
1
car speed 0 km/h
2
car speed 27 km/h
3
car speed 54 km/h
4
car speed 81 km/h
5
car speed 108 km/h
6
car speed 135 km/h
Driving direction is left to right, the timing sequence is top-down.
You can see: traffic jam moving to the left, though the cars moving to
the right.
More information you'll find in the related Wikipedia entry.