What could you change to make traffic jams move forward rather than backward? What could you change to minimize the chances of traffic jams forming? Can you explicitly encode these into the model? ![]() The asymmetry between acceleration and deceleration is a simplified representation of different driving habits and response times. Try giving different rules or ACCELERATION/DECELERATION values to some of the cars. In reality, different vehicles may follow different rules. Is the rule presented here realistic? Are there other rules that are more accurate or represent better driving strategies? Try other rules for speeding up and slowing down. At what point does the flow "break down"? EXTENDING THE MODEL What happens to the flow? Gradually increase DECELERATION while the model runs. Which variable has the greatest effect? Do the patterns make sense? Do they seem to be consistent with your driving experiences? Look for patterns in how these settings affect the traffic flow. In this model there are three sliders that can affect the tendency to create traffic jams: the initial NUMBER-OF-CARS, ACCELERATION, and DECELERATION. This is typical of traffic flow models.Įven though both ACCELERATION and DECELERATION are very small, the cars can achieve high speeds as these values are added or subtracted at each tick. Notice that the default settings have cars decelerating much faster than they accelerate. Notice not only the maximum and minimum, but also the variability - the "jerkiness" of one vehicle. The speed of a single car (turtle 0), painted red so it can be watched. The fastest speed of any car (this doesn't exceed the speed limit!) The plot shows three values as the model runs: 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. If some cars are clustered together, they will move slowly, causing cars behind them to slow down, and a traffic jam forms.Įven though all of the cars are moving forward, the traffic jams tend to move backwards. Traffic jams can start from small "seeds." These cars start with random positions and random speeds. How much slower it goes than the car in front of it is controlled by the DECELERATION slider. When a car sees another car right in front, it matches that car's speed and then slows down a bit more. The ACCELERATION slider controls the rate at which cars accelerate (speed up) when there are no cars ahead. Note that they wrap around the world as they move, so the road is like a continuous loop. Set the NUMBER-OF-CARS slider to change the number of cars on the road.Ĭlick on GO to start the cars moving. HOW TO USE ITĬlick on the SETUP button to set up the cars. No "centralized cause" is needed for a traffic jam to form. ![]() The model demonstrates how traffic jams can form even without any accidents, broken bridges, or overturned trucks. Each car follows a simple set of rules: it slows down (decelerates) if it sees a car close ahead, and speeds up (accelerates) if it doesn't see a car ahead. This model models the movement of cars on a highway. You can also Try running it in NetLogo Web If you download the NetLogo application, this model is included.
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