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Speed Estimation Techniques

Speed Estimation Techniques. Mathematical Equations A simple relationship between speed and flow. Linear, logarithmic, exponential, power, polynomial, conical and etc Mathematical equations do not incorporate link operational characteristics. Standard BPR based on volume/capacity ratio.

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Speed Estimation Techniques

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  1. Speed Estimation Techniques

  2. Mathematical EquationsA simple relationship between speed and flow Linear, logarithmic, exponential, power, polynomial, conical and etc Mathematical equations do not incorporate link operational characteristics.

  3. Standard BPRbased on volume/capacity ratio

  4. METRO Updated BPR based on volume/capacity ratio

  5. Davidson-Akcelik Modelbased on queuing theory for v/c<1 Delay parameter Free flow travel time Degree of saturation or v/c

  6. Akcelik Modelbased on queuing theory for v/c>1 Delay parameter Time Period of Analysis Degree of saturation or v/c Free flow travel time Capacity (vph)

  7. Van Aerde Modelbased on Kinematic Car-Following Model for v/c<1 Basically it is a quadratic equation only for v/c<1 which has four parameters of free flow speed, speed at capacity, capacity, and jam density.

  8. The Issue of Capacity Reach Most of the models work well for v/c smaller than 1. As soon as v/c gets closer to 1 the difference between models gets larger. For v/c greater than 1, some models do not work at all and some others have large differences. So we should separate the relationship into two regimes of v/c<1 and v/c>1. However for planning applications, any improved equation must be a monotonically decreasing/increasing and continuous function for the equilibrium assignment process to arrive at a unique solution.

  9. The Issue of Capacity Reach Therefore for v/c greater than 1, queuing theory should be incorporated. Akcelic model is the only one that is based on queuing theory and thus, is the only model that properly predicts speed for v/c>1 conditions. Akcelik paper(s) should be reviewed to learn about his methodology in using queuing theory.

  10. The Issue of Capacity Reach Theoretically queuing theory can be used to predict speeds but using loop detector data to study the relationships between travel time and flow based on queuing theory may be challenging. Why? Because the volumes used in traffic assignment algorithms represent demand while the volumes detected by loop detectors do not represent demand. A spatiotemporal method should be used to incorporate queuing theory in order to calculate the queuing delay.

  11. Questions • Paper (e), page 113, figure 3, how they calculated travel time based on the queuing theory? • Literature suggested to remove all the data came from congested times because of the volume problem of loop detectors that do not represent demand and therefore real travel time. Is it right?

  12. What To Do: Pilot StudyPlot similar graphs from other papers using some data

  13. What To Do: Pilot StudyPlot similar graphs from other papers using some data

  14. What To Do: Pilot StudyPlot similar graphs from other papers using some data

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