33.3. Calibration of Greenshield’s Model

Try these first

1. 1.

   What is free flow speed?

   Hint

   Think about the speed limit on an uncongested highway.

2. 2.

   Define jam density.

   Hint

   What happens when cars line up back to back?

3. 3.

   What does free flow speed represent?

   • The speed in congested conditions
   • The maximum speed in ideal traffic
   • The minimum speed on highways

   Hint

   Think about what happens when traffic is uninterrupted.

4. 4.

   True or False: Jam density can be defined as the density of vehicles at full congestion.

   • True
   • False

   Hint

   What happens when cars are bumper to bumper?

5. 5.

   A traffic study collected the following speeds and densities: (10 km/h, 150 veh/km), (20 km/h, 200 veh/km), and (30 km/h, 100 veh/km). Use linear regression to find a and b coefficients.

   Hint

   Focus on organizing your data first before plugging into the formulas.

6. 6.

   If your calibrated model predicts a free flow speed of 50 km/h and jam density of 250 veh/km, calculate the maximum flow rate.

   Hint

   Remember to apply the formula for max flow appropriately.