Aims and Objectives
The highways part of the module aims to provide students with a basic understanding of highway design and construction, an understanding of the practices associated with highway route selection, the analysis of traffic flows, vehicular behavior, highway capacity and related issues of environment and sustainability.
Outcomes:
1. Discuss methods of transport planning process and highway planning strategies.
2. Apply and evaluate methods of analysis of highway traffic and signalized intersections.
3. Evaluate the principles of highway alignment, and carry out geometric design and intersection designs, including environmental aspects.
Introduction:
The road network of any city is its lifeline and the evaluation of their performance is very necessary for future traffic planning, design, operation and maintenance. Traffic congestion is the common problem of most urban area in Oman; most of the roads are congested.
The following project should be solved individually. In the project, students will have hands-on experience in discussing methods of transport planning process, evaluate methods of analysis of highway traffic and signalized intersections, and carry out geometric design and intersection designs.
Data:
Each student will have his own data that is given in the attached "CourseWork Project-Data" Excel sheet.
Transport Planning and Geometric Design of Highway
1. Task I
The AASHTO publication A Policy on Geometric Design of Highways and Streets provides the standards for geometric design of highways. It is planned to construct a rural collector highway between Muscat and Nizwa in in an area of rolling terrain.
1. Describe the three categories of information about the characteristics of the area of a proposed highway location that can be assembled in the office prior to any field survey activity.
2. To determine the ADT on the road, the data was collected as shown below on a Tuesday during the following.
Table 1: Traffic volume at specific time
|
7:00-8:00 a.m.
|
8:00 -9:00 a.m
|
9:00-10:00a.m
|
10:00-11:00 .m
|
11:00 -12 noon
|
|
150
|
120
|
130
|
50
|
20
|
3. In this situation, determine the following design values.
i. Minimum design speed
ii. Recommended lane width
iii. Preferable shoulder width
iv. Right of Way
v. Maximum grade
I. Determine the minimum length of a crest vertical curve and sage vertical curve if the grades are
Table 2: grades for the curve
|
Up fill grade
|
Down fill grade
|
|
+4
|
-2
|
Consider the following for the sage vertical curve criteria :(a) Stopping sight distance,(b) Comfort
(c) General appearance
2. Task II
1. Determine the free flow speed, density, and level of service for an urban freeway segment between Muscat and Al Batina.
Table3: Traffic characteristics of the Segment.
|
Traffic volumes (two-way)
veh/h
|
Trucks
%
|
Terrain
|
PHF
|
Number of lane in each
direction
|
Lateral clearance
|
Ramp density
|
Composition of driver population
|
|
4000
|
10%
|
Level
|
0.95
|
3
|
3 m
|
4/1.5 mi
apart
|
Familiar
driver.
|
3. Task III
1. You have been hired as a consultant to a medium-sized city to develop and implement a procedure for evaluating three alternatives to replace an existing two-lane highway with a four-lane highway that will meet current design standards are proposed. The selected alternative will provide a more direct route between two towns that are 12.0 miles apart along the existing highway. With each alternative operating speeds are expected to be at or near the design speed of 60 miles per hour. Develop the scores for each alternative and recommend a preferred alternative for development. The following scoring method, developed by the transportation oversight board, is to be used
Table 5: Ranking and Weights for Each Objective
|
Evaluation
Criterion
|
Performance Measure
|
Weight (%)
|
|
Mobility
|
Travel time of shortest travel time alternative divided by
travel time of alternative i
|
25
|
|
Safety
|
Annual reduction in number of crashes of alternative i
divided by highest annual reduction in number of crashes among all alternatives
|
25
|
|
Cost- effectiveness
|
Project development cost of least expensive alternative (in $ per mile) divided by project development cost of
alternative i (in $ per mile)
|
20
|
|
Environmental impacts
|
Area of wetlands impacted of least-impacting alternative divided by area of wetlands impacted by
alternative i
|
15
|
|
Community impacts
|
Number of business and residences displaced by least impacting alternative divided by number of businesses
and residences displaced by alternative i
|
15
|
The following information has been estimated for each alternative by the planning staff:
Table 6: Estimated Values for Measures of Effectiveness
|
Property
|
Alt. 1
|
Alt. 2
|
Alt. 3
|
|
Cost of development
|
$10,900,000
|
$18,400,000
|
$16,900,000
|
|
Length
|
11.2 miles
|
9.8 miles
|
10.1 miles
|
|
Annual crash reduction
|
10
|
17
|
19
|
|
Business
displacements
|
3
|
4
|
5
|
|
Residential
displacements
|
4
|
3
|
3
|
|
Wetlands impacted
|
1.5 acres
|
3.9 acres
|
3.9 acres
|
2. Write a short report for a comparative evaluation of the impacts of the project on Social and Natural Systems
1. Task I
2 Intersection Design
a. Describe the different principles involved in the design of at-grade intersections and the different types of at-grade intersections. Also, give an example of an appropriate location for the use of each type.
b. A minor road intersects a multilane divided highway at 90° forming a T intersection. The speed limits on the major and minor roads are 55 and 35 mi/h, respectively.
- Design the minimum sight distance required for a single-unit truck on the minor road to depart from a stopped position and turn left onto the major road. Discuss additional consideration should be given to the sight distances computed for the design vehicle crossing the intersection.
- For the design determine the sight distance required by the minor-road vehicle to safely complete a right turn onto the major road.
- Discuss the changes if the intersection is an oblique intersection with an acute angle of 35°.
Table 7: characteristics of the intersection
|
Major Road ml/hr
|
Minor Road ml/hr
|
Type of vehicle
|
Angle
|
|
55
|
35
|
Single unit truck
|
35°
|
2. Task II
1. Design a suitable signal phasing system and phase lengths for the intersection using the Webster method. Show a detailed layout of the phasing system and the intersection geometry used for the geometric and traffic characteristics shown below.
Table 8:The geometric and traffic characteristics of the intersection
|
Approach (Width)
|
North (56ft)
|
South (56 ft)
|
East (68ft)
|
West (68ft)
|
|
Peak hour approach
volumes
|
|
|
|
|
|
Left turn
|
133
|
73
|
168
|
134
|
|
Through movement
|
420
|
373
|
563
|
516
|
|
Right turn
|
140
|
135
|
169
|
178
|
|
Conflicting pedestrian
volumes
|
900
|
1200
|
1200
|
900
|
|
PHF
|
0.95
|
0.95
|
0.95
|
0.95
|
Assume the following saturation flows:
Table 9: The saturation flow of the intersection
|
Through lanes veh/ln/h
|
Through and right lanes veh/ln/h
|
Left lanes veh/ln/h
|
Left and through lanes
veh/ln/h
|
Left, though, and right lanes
veh/ln/h
|
saturation flow rates
%
|
|
1600
|
1400
|
1000
|
1200
|
1100
|
10
|
2. If saturation flow rates that are 10% higher. What effect does this have on the cycle length?
3. Task III : Evaluating the Alternatives
1. A two-lane minor street crosses a four-lane major street. If the traffic conditions are as given, determine whether installing a traffic signal at this intersection is warranted.
- The traffic volumes for each eight hours of an average day (both directions on Major Street) total 400 veh/h. For the higher volume minor-street approach (one direction only), the total is 100.
- The 85th-percentile speed of major-street traffic is 43 mi/h.
- The pedestrian volume crossing the major street during an average day is 450 d/h during each any four hours.
- The number of gaps per hour in the traffic stream for pedestrians to cross during peak pedestrian periods is 52.
- The nearest traffic signal is located 137 m from this location.
Note:
- This submission should include full solutions including calculations for each of the problems presented. All solutions should clearly state any assumptions, clauses, tables, figures and formulas used.
- All the design should be clearly illustrated.
- You must have citations from reputable journals, articles, books, etc. in your paper. this is considered of great importance in the quality of your report and hence your mark
Report Format
- Number of pages: Maximum 15 pages including references list and the appendix (if any).
- Line spacing: Generally use 1.5 x line spacing.
- Start with the title page (including your name) or student number as requested.
- It is preferable to place figures within the text rather than group them at the end of the report.
- Give a sequential number to all figures (Fig. 1, Fig. 2, Fig. 3, etc.)
- Add a brief, informative caption to the figures.
Guidelines:
Follow the guidelines mentioned below during writing your case study:
- The report should have a Title Page. Title Page should contain the following information.
- Use page numbers
- Use your own words on writing, Times New Roman font size 12
- Heading should be with Font Size 14, Bold, Underline
- Use Diagrams and Examples to explain your topic.