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CE 2710
Introduction to Transportation Engineering
Homework 8
due Wed November 04
Question 1 - Directional Distribution

  • Calculate the directional distribution of traffic on the east-west highway shown in the image in the attached link.   Assume that the number of vehicles shown in each direction is proportionate to the traffic flow during the peak hour for traffic.  Report the results as the proportion of traffic in the peak direction.

  • Two roads carry 1000 vehicles/hour in the peak hour.  The directional distribution is 0.7 on road A and 0.6 on road B during the peak hour of travel.  Which of the two roads, A or B, will be the most congested during the peak hour?

  • Road X connects two towns, one of which is completely residential and the second consists only of businesses.  Road Y also connects two towns but in this case both town are mixed use.  Which of these two roads, X or Y, would have a higher directional distribution in the peak hour?  Why?

Question 2 (corrected)
  • Estimate the traffic concentration in both directions on the roadway shown in the image from Question 1.  If the average speed in the east-west direction is 20 mph and 35 in the west-east direction estimate the traffic flow per hour in each direction.  (This question requires you to estimate distance along the road.  This will take some creativity! Each lane should be treated seperately.)

  • A permanent count station on I-84 in Tolland shows that a total of 11 million vehicles traverse this roadway each year.  Calculate the AADT for this stretch of road.

Question 3 - Design Hour Volume
  • Two new roads are being designed.  Both roads, T and R, are expected to each carry traffic volumes of 10,000 vehicles per day.  Road T is expected to have average fluctuation in traffic volume over the course of the year, while Road R will have more than average fluctuation.  Assume that the design hour is taken as the 100th busiest hour of the year.  Use the AASHTO graph given in the images for HW 8 file to estimate the % of traffic in the design hour as a percentage of the AADT.  Calculation the design hour traffic for both of these roads. 

  • Repeat the above calculations using the 20th busiest hour of the year as the design hour.

  • Which assumption, using the 20th or the 100th busiest hour, would result in the design of a larger road way?

  • How many hours in the year would there be less traffic than in the design hour If the 20th hour is used as the design hour?

Question 4


  • Estimate the design hour volume (DHV) in the design direction for a new road given that the estimated AADT = 25,000, and the directional split is 0.60:0.40.  Use the 60th hour as the design hour and estimate the relationship between AADT and design hour using the AASHTO chart given in the images for HW 8 file.  Assume that the line for average conditions applies to this new road.

  • Based on the DHV calculated above determine the number of lanes that should be provided in each direction to carry this traffic at a LOS E.  What is the design hour service volume (DHSV) in this case?

The maximum volume for each level of service on this type of road is given below.

LOS C 290, LOS D 780, LOS E 880, LOS F >880

  • Would you need to provide more lanes or less lanes if a LOS C is used instead of LOS E.

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