TRAFFIC CONTROL DEVICES

Excessive delay is becoming a problem at many intersections in Mythaca, especially near the Mythaca State University campus. The Mythaca County staff has recently obtained a pair of video tapes that show vehicles approaching and entering an intersection near another university campus. We would like you to help us determine the relationship between delay calculated two different ways:

• Observing individual vehicles on video tape
• Using the estimation method in the SNotes, pages 2.3.1-2.3.4

(signed) Jon D. Fricker
Mythaca County Engineer

1. (10 points) Traffic Control Devices (TCDs). A pedestrian and bicycle trail leading to and from the Celery Bog Nature Center, as planned, must cross Lindberg Road about 625 feet east of a crest vertical curve. (The crossing would be located at the west edge of the Purdue Golf Course, just east of 1600 Loindberg Road.) The crest V.C. is severe enough (G1=0%, G2=-2%) that hikers/bikes and motorists cannot see each other until an eastbound vehicle has reached the crest of the hill. The speed limit on this part of Lindberg Road is 40 mph, but many vehicles are driven at 50 mph. Using the "Signman" Web Site as your resource, select the TCD(s) that should be placed on the EB approach to the hiker/biker crossing for EB drivers to see. Identify the TCD(s) by the letter-number code that appears to the right of each TCD displayed by "Signman". (Example from SNotes page 9.1.3: Right turn advance warning sign = W1-1R; Left turn warning sign would be W1-1L.) In addition, where (i.e., distance from the crossing, distance from the roadway edge, height of sign) should the TCD be placed? Explain why you chose the TCD(s) and the location you did.
   
   
2. (15 points) Phases and Intervals in Traffic Signal Timing Using the prescribed format, create a Traffic Signal Timing Diagram for the intersection of Stadium Avenue and Northwestern Avenue for any day and time of day you choose. Note: You will have to add extra columns for each movement that has its own signal phase, such as the "NB-WB LT Veh" approach on NB Northwestern.
   
   
3. Computing Vehicle Delay from Direct Observation of Individual Vehicles (DOIV). From the Instructional Media Center in HIKS, check out the video cassettes with Shelf Numbers IM522VC ("Upstream") and IM523VC ("Stop bar") For a guide to viewing the video tapes, click here.)
   • A. (15 points) Beginning at the start time assigned to your group, record the key events associated with the first 40 EB vehicles on the "stop bar" video that enter the intersection (with the intention of turning left). Record these events in a spreadsheet, as shown in the attached example. (A version that looks more like a spreadsheet will be posted on the solutions board.)
   • B. (10 points) In your spreadsheet, carry out the calculations for the three rightmost columns in the data sheet. In addition, what is the average delay experienced by the 40 vehicles?
   • C. (5 points) When the spreadsheet is completed, email it in a readable form to "fricker" and attach a hard copy to your report.
   
   
4. Estimating Vehicle Delay by Periodic Observation (PO). Use the method on SNotes pages 2.3.1 to 2.3.4 and an interval of 15 seconds, estimate the delay experienced by the 40 vehicles that you observed in the DOIV problem above. If your 40 vehicles do not span a time period of at least 2 minutes and 30 seconds, extend your observations on the video tape as necessary.
   • A. (10 points) Submit a photocopy of Figure G-10 (SNotes 2.3.4), as you used it in your analysis. Explain clearly how you defined and determined the V(s) value at each time interval.
   • B. (10 points) What is the average delay experienced by the 40 vehicles according to the PO method? How does this value of delay compare with the value found by the DOIV method?
   
   
5. (15 points) Time Space Diagrams (TSDs). The signals at the intersection of Stadium Avenue and University Street are currently "traffic actuated", If they were to be converted to "pretimed" operation, it would be wise to coordinate these signals with those at Northwestern. Assume that the G+Y time allotted to The Stadium approaches at University will be the same as at Northwestern. Do the calculations and draw the corresponding TSD that shows the best offset for these two signals, such that as much E-W traffic as possible can have both lights be green and (b) the speed limit on Stadium is not exceeded. What is the value of the offset?