CE361 Introduction to Transportation Engineering

Out:  Friday 11 October 2002

Homework 5

Due:  Friday 18 October 2002

 

HIGHWAY SAFETY AND PROJECT EVALUATION

 

Dear Consultant:

 

Traffic safety can be an emotional issue.  Identifying hazardous locations and deciding where to apply limited finds must withstand the scrutiny of concerned citizens.  In this HW, you will be asked to implement certain elements of the Highway Safety Improvement Program framework (CNotes Figure 6.4).  Please complete the exercises below completely and clearly.  You may work in a group of CE361 students not to exceed two in size.  The usual rules about signatures and labeling each problem apply.

 

 

1.       Collect and maintain data.  Each year, local law enforcement agencies supply the Mythaca Regional Planning Commission (MRPC) with crash data for roads and intersections within the County.

  1. (10 points) Crash data for the intersection of Dewey Avenue and Gustav Street for the last four years are 6, 4, 11, and 8.  The two-way ADT for the four approaches are 5846, 6163, 8862, and 6265.  What is the crash rate for this intersection?
  2. (10 points)  A 1.8-mile section of Quigley Road that connects Mythaca with a suburban development has experienced 27 crashes during the last two years.  The two-way ADT on the road section is 6410. .  What is the crash rate for this section of Quigley Road?

 

2.       Identify hazardous locations.  Use Critical Rate Analysis to determine whether the sites in Problem 1 are hazardous.

A.      (10 points) Nine intersections with characteristics similar to Dewey and Gustav had RMEV crash rates 5.9, 3.9, 3.9, 3.4, 1.5, 8.8, 7.0, 6.0, and 2.3.  Use the 95 percent confidence level and (regardless of your answer to Problem 1A) a crash rate of 6.4.  Is the Dewey and Gustav intersection hazardous?

B.      (10 points) Seven road segments with characteristics similar to the 1.8-mile section of Quigley Road had RHMVM crash rates of 57.6, 283.8, 305.1, 224.2, 54.5, 56.9, and 74.9.  Use the 95 percent confidence level and (regardless of your answer to Problem 1B) a crash rate of 231.4.  Is the Quigley segment hazardous?

 

3.       Conduct engineering studies.

  1. (5 points) Collision diagrams.  In CNotes Figure 6.6, on which dates did left-turn head-on collisions occur?
  2. (10 points) Causes and countermeasures.  What are four possible causes of left-turn head-on collisions?  For two of the causes, propose a countermeasure.

 

4.       Establish project priorities. 

  1. (10 points)  Crash Reduction Factors.  On two different sections of SR361, a particular countermeasure was installed.  The crash rates for the three years before and three years after the installation are given below.  Compute the Crash Reduction Factors for each of the two sections.

Year:

1

2

3

4

5

6

Section 39.3

50.0

50.4

55.2

45.2

41.5

39.5

Section 8.0

68.5

67.5

59.9

27.6

35.9

46.1
  1. (10 points)  Crashes prevented.  A section of road has a current ADT of 5650 and a HMVM crash rate of 71.6.  If a countermeasure with a Crash Reduction Factor of 20.9 percent is applied and ADT is expected to be 7430 ten years from now, how many crashes will have been prevented?  Assume the ADT will grow at a constant rate over the ten years.
  2. (10 points)  Project selection.  It has been determined that an intersection needs to have a traffic signal installed.  Signal A will cost $75,778 to install and $1115 per year to maintain.  Signal B will cost $86,506 to install and $950 per year to maintain.  If the signal is supposed to last ten years before possible replacement, and the discount rate is 4.6 percent, which signal (A or B) has lower Present Worth of Costs?

 

5.       Traffic Conflict Analysis.  The intersection of X and Y has not had many crashes, but “everybody knows” it is dangerous.  A team of observers went to the intersection for six hours to collect traffic conflict data.  They observed 33 conflicts among an average of 1560 entering vehicles per hour.  The 33 conflicts were categorized as shown in the table below.

Severity

TTC

ROC

1

15

15

2

14

17

3

4

1

Total

33

33
  1. (5 points) Calculate Average Hourly Conflicts and AHC per Thousand Entering Vehicles.
  2. (5 points) Calculate Total Conflict Severity and Overall Average Conflict Severity.
  3. (5 points) What is the Intersection Conflict Index for the intersection?  Does this result confirm that the intersection is dangerous?