CE 572 - Intersection Traffic Operations
Spring 2007

Website of the day:
Berkeley Highway Laboratory

Objectives for today:

• to learn how to interpret data and relate results to traffic signal timing and traffic flow/operations

Topics:

• Review results of Assignment 3 from last time
• Begin group work for Assignment 4

Assignment 4
This assignment will be due at the beginning of class on Thursday, February 8th (electronically to me by noon and with copy in class).  You will complete this assignment working in the following teams.  Each team has the same assigned direction (2 or 4) and lane type (TH or LT)

• Team 1: Ochoa, Amin
• Team 2: Perez, Chipman, Taylor
• Team 3: Rahman, Ekhator
• Team 4: Guo, Madrigal
• Team 5: Nayak, Sekulic

Prepare your work in an Excel document with one page for each of the seven questions. All answers should be complete but as brief as possible. The supporting charts should be included. One assignment should be submitted per group. Data from each group member should be used in preparing answers.

Answer the following questions based on the data that you and your team members have generated in Assignment 3.

1. Did you observe any lane changing behavior in your time-space plots?

2. How do you determine whether a vehicle is part of the queue; what criteria can you use to make this determination?

3. How do you explain the variation in headway by LocalY? Do you data conform to your expectations? If not, why not? Do you see any differences between the first several headway measurements and later measurements? If so, can you explain these differences?

4. Based on your observations in Q3, prepare a theoretical curve that represents the change in headway vs. distance upstream from the stop bar. Prepare a brief discussion explaining the basis for this curve.

5. Explain the basis for the variation in mean headway by position in queue. Why is this variation important to understand, when you consider signal timing? Based on your assessment, prepare a general curve that shows this theoretical variation.

6. How does your estimate of the saturation headway compare with the HCM ideal value of 1.9 seconds? Propose factors that would cause differences between your estimate and the HCM value.

7a. Select the time interval in your data set with the largest number of vehicles in queue. Using the time-space plot (LocalY vs FrameID), focus in on the following two spatial and temporal ranges: Space: 10’ downstream of the stop bar to 100’ upstream of the stop bar. Time: 1 sec before movement of the first vehicle in queue to the departure of the last vehicle in queue at a point 10’ downstream of the stop bar.

7b. Select the X and Y axis ranges Major distance unit: 25’ Minor distance unit: 1’ Major time unit: 10 Minor time unit: 1

7c. Show gridlines, so that 1’ and 0.1 second grids are visible on your chart.

7d. Prepare a graphic showing the detection zone status (either occupied or unoccupied) for two detection zone lengths (22’ and 66’). Prepare brief comments on the results, particularly on the relationship between detection zone length and unoccupancy time.

Class notes:
Written notes
Slides

Questions on today's class:
1. After running the VB code on the unsorted data, it generated a category labeled case. What are these values?
Response: The case number was a programming aid for me as I was developing the code.  It doesn't have much meaning other than that.

2. Aren't Q4 and Q5 more or less the same? What exactly is required?
Response: Question 4 addresses the change in headway for one vehicle as it progresses toward the stop bar, while question 5 addresses the differences in headway at the stop bar for different vehicles (according to their position in queue).  Both are of interest.