Homework 2 (HW 2) w/ #2 revised / Due: Mon. 15 September 2008
TRAFFIC FLOW DATA
· You will be permitted to submit this HW with one or two other CE361 students. If the HW is submitted by more than one student, the signatures of those students must appear at the top of the front page of the materials submitted. By their signatures, the students certify that (a) they approve of what is being submitted, (b) they will accept the same grade that is awarded for the HW, and (c) each student is responsible for having the HW content available at a subsequent test.
· For every problem, identify the problem by its number and name, be clear, be concise, cite your sources, attach documentation (if appropriate), and let your methodology be known. Points may be deducted.
· “FTE” = Fundamentals of Transportation Engineering, the textbook for CE361.
1. (10 points) Mr. Posey’s letter. (link) What is the minimum number of vehicle speeds to record to determine the 85th percentile speed on South 24th Street? For E, use 1 mph. For standard deviation S, use the largest value found by Darren in FTE Table 6.15.
2. Occupancy and density from loop detectors. A loop detector with an effective length of 7.0 feet is actuated for 4.8 percent of a one-hour study period. During this time, 632 vehicles were detected by the loop. Their mean speed was 63.2 mph and their mean length was 18.24 feet.
A. (10 points) Convert the apparent occupancy rate to the actual occupancy rate.
B. (10 points) What was the density (vpm) on the roadway during the occupancy measurements?
3. (45 points) Speed-Flow-Density relationships. Do FTE Exercise 2.40, but use the data emailed to you.
4. The road to Shreveport. It is 343 miles (552 km) from New Orleans to Shreveport. Normally (according to mapquest.com), it takes 5 hours and 21 minutes to drive this distance. On the Saturday before Hurricane Gustav reached the Louisiana Coast, it took one woman 25 hours to drive that distance. Although not all segments of I-10 and I-49 between New Orleans and Shreveport are the same, let us choose one ten-kilometer segment of I-10 in Ascension Parish (2 lanes each direction) and treat it as representative of the entire trip. (If we can analyze one segment, we can analyze any other.) The Ascension Parish Engineer says the Greenshields equations shown below are adequate representations of the traffic flow on the 10-kilometer segment we are studying. Note: The equations use metric distances.
(2.13) ; (2.19) ; (2.18)
A. (10 points) Under normal conditions, what is the mean speed of the trip to Shreveport? What is the corresponding traffic density and flow rate on the 10-kilometer segment, according to the Greenshields equations?
B. (10 points) On the pre-Gustav trip to Shreveport, what was the mean speed? What would be the corresponding traffic density and flow rate on the 10-kilometer segment, according to the Greenshields equations?
C. (5 points) Do all the values you calculated make sense? (Are any suspicious?)