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.
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. For a 4.5 mi two-lane highway segment in level terrain in Muscat. Determine the PTSF If
Table3: Traffic characteristics of the Segment.
|
|
Traffic volumes (two- way) veh/h
|
Trucks %
|
RVs%
|
PHF
|
directional split
|
no-passing zones
|
|
|
1100
|
10%
|
7%
|
0.97
|
60/40
|
40%
|
|
|
2. Estimate the ATS for.
Table4: Geometric characteristics of the Segment.
|
Speed
|
lane width
|
shoulder width
|
access point
|
|
56
|
11
|
3
|
12
|
3. Compute: LOS, v/c, veh-mi in peak 15 min and peak hour, and total travel time in peak 15 min.
4. Describe the traffic characteristics associated with the LOS for your two-lane highways.
5. Using the previous data, determine PTSF and ATS in the peak direction if northbound volume = 1000 veh/h and southbound volume 600 veh/h.
6. Finally determine the level of service of a two-lane section if a passing lane 1.5 mi long is added. The passing lane begins 0.75 mi from the starting point of the analysis segment.
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
|
Annual reduction in number of crashes of alternative i divided by highest annual reduction in number of crashes among all alternatives
|
20
|
|
Environmental impacts
|
Annual reduction in number of crashes of alternative i divided by highest annual reduction in number of crashes among all alternatives
|
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
2 Intersection Design
Task I
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. Three designs have been proposed to improve traffic flow at a major intersection in a heavily traveled suburban area. The first alternative involves improved traffic signaling. The second alternative includes traffic-signal improvements and intersection widening for exclusive left turns. The third alternative includes extensive reconstruction, including a grade separation structure. The construction costs, as well as annual maintenance and user costs, are listed in the following table for each alternative. Determine which alternative is preferred based on economic criteria if the analysis period is 20 years and the annual interest rate is 15%. Show that the result is the same using the present worth, equivalent annual cost, benefit- cost ratio, and rate-of-return methods.
Table 9: Cost and Benefits for Improvement Plans with Respect to Existing Conditions
|
Alternative
|
Capital Cost ($)
|
Annual Maintenance Cost ($)
|
Annual User Cost ($)
|
Salvage Value ($)
|
|
Present condition
|
0
|
15,000
|
500,000
|
0
|
|
Traffic signals
|
440,000
|
10,000
|
401,000
|
15,000
|
|
Intersection widening
|
790,000
|
9000
|
350,000
|
11,000
|
|
Grade separation
|
1,250,000
|
8000
|
301,000
|
0
|
2. You are asked to develop and implement a procedure for evaluating the previous project, write a short report describing your proposal and recommendation as to how the city should proceed with this process.
3 Parking Design
1. Briefly describe the tasks should be included in a comprehensive parking study for your college campus, describe how you would perform each task and the way you would present the data collected.
2. Select a parking lot on your campus. For several hours, conduct a study of the lot using the methods described in this chapter. From the data collected, determine duration, turnover, Occupancy, Parking capacity, and Efficiency. Draw a parking accumulation curve for the lot.
3. Select a parking lot on your campus (specify with illustration), calculate total number of Cars that park between 8 a.m. and 4 p.m or 4:00pm to 8:00 pm.
I. Calculate the percentage of these cars that park for an average of 2 hr, 4hr, 6hr, and 8hr.
II. Determine the space-hours of demand at the lot.
III. If 10% of the parking bays are vacant on average (between 8 a.m. and 12 p.m.) at the parking lot, determine the number of parking bays in the parking lot. Assume an efficiency factor of 0.85.
IV. MEC is planning an expansion of her lot to provide adequate demand for the following 5 years. If it has been estimated that parking demand for all categories will increase by 5% a year, determine the number of additional parking bays that will be required.
Table 10: percentage of parking demand and parking bay
|
% of parking bay
|
parking demand %
|
|
10
|
5
|
Attachment:- Highway and transportation engineering.xlsx