WHAT IS IT? ----------- This project is a more sophisticated of the basic StarLogo model 'traffic'. Much like traffic, this model demonstrates how traffic jams can form with two lanes, and how drivers can react by changing lanes, although this often does little to solve their problem. Again, no centralized cause may be responsible for the slowdown of traffic. HOW TO USE IT ------------- Click on the SETUP button to set up the cars. Click on DRIVE to start the cars moving. The STEP button performs the all the drive functions, for just one tick of the clock. The NUMBER slider controls the number of cars on the road, and C-TYPES determines their appearance. The LOOKAHEAD slider controls the distance that drivers look ahead (in deciding whether to slow down or change lanes). The SPEEDUP slider controls the rate at which cars accelerate when there are no cars ahead. The SLOWDOWN slider controls the rate at which cars decelerate when there is a car close ahead. The DELAY slider determines the time delay between clock ticks. Slow down the simulation to watch the behavior of certain cars more closely. THINGS TO NOTICE ---------------- Traffic jams can start from small "seeds." Cars start with random positions and random speeds. If some cars are clustered together, they will move slowly, causing cars behind them to slow down, and a traffic jam forms. Even though all of the cars are moving forward, the traffic jams tend to move backwards. This behavior is common in wave phenomena: the behavior of the group is often very different from the behavior of the individuals that make up the group. Just as each car has a current speed and a maximum speed, each driver has a current patience and a maximum patience. When a driver decides to change lanes, he may not always find an opening the the lane. When his patience expires, he tries to get back in the lane he was first in. If this fails, back he goes... As he gets more 'frustrated', his patience gradually decreases over time. When the number of cars in the model is high, watch to find cars that weave in and out of lanes like this. EXPLORATIONS ------------ * What could you change to minimize the chances of traffic jams forming, besides just the number of cars? What is the relationship between number of cars, number of lanes, and (in this case) the length of each lane? * Try to create a 'traffic-3 lanes', 'traffic-4 lanes', or 'traffic-crossroads' model. * Note that the cars never crash into each other- a car will never enter a patch or pass through a patch containing another car. Remove this feature, and have the turtles that collide die upon collision. What will happen to such a model over time? STARLOGO FEATURES ----------------- The turtles/cars use SPEED-AT to find out the value of the SPEED variable for other turtles/cars. Each turtle has a shape unlike the turtles from other StarLogo models. Each patch size is 8 by 8 pixels, instead of the standard 4 by 4. StarLogo uses SETSHAPE to alter the shapes of turtles. You can, using the toolbar, create your own turtle shapes or modify existing ones. It should be relatively straightforward to modify the code of 'traffic-2 lanes' to include your own shapes.