Data was collected from an observation station on GA-400, a toll road just north of Atlanta.

The traffic flow at this location is illustrated in the figure on the following page. The orange

observations on the figure represent the field observations and the curve (in blue) represents

a fitted equilibrium model.

a) Label and determine the following: free-flow speed, jam density, capacity, optimal

density, and optimal speed.

b) Use the estimated free-flow speed and jam density to construct Greenshield's model:

i. Write the mathematical equation of the model and derive the other two pairwise

relationships.

ii. Draw the corresponding curves implied by Greenshield's model. You may draw

on top of the existing plots or create new ones.

iii. Compute capacity, optimal density, and optimal speed according to Greenshield's

model.

iv. Check the computed capacity against the capacity on the curves that you draw

and determine if they match.

c) Comment on how the two models compare in terms of fitting the empirical data. Based

on the notes, can you determine the model represented in blue?