0

Centennial

Transportation Extension of the SR-241 Toll Road

Engineers:

Alireza Behbahani

Megan Hanrahan

Sarah Kevorkian

Kevin Kirk

Chosita Sribhibhadh

1

Executive Summary

The transportation engineers at Centennial Transportation were charged with the task of

designing a two lane highway extension of the toll road SR-241 that would connect it to SR-74,

the Ortega Highway. This extension, approximately 4 miles long, would span along the Cota de

Caza mountainous terrain. In order to devise the desired design that would allow a converging

path joining the 241 and 74 corridors, it was necessary for the specific safety and design

standards of Caltrans and AASHTO to be satisfied while producing the project plan. It was also

important to take into consideration the environmental impacts of this freeway which would span

along untouched nature inhabited by many forms of wildlife. The challenge before us was to

meet standards, please nearby residents, environmentalists, and future travelers of the road all

while keeping construction cost and time at a minimum to increase efficiency. A more detailed

description of the design standards that we went by is given in Chapter One of this report.

The five skilled engineers that worked on this project started off by discussing

environmental concerns. It would have been easiest just to construct the highway along the path

with the most consistent elevation, but we wanted to take into consideration the surroundings of

the highway that residents use every day. Once we factored in the surrounding area of the

highway, we were then able to choose a path connecting the corridors. This straight path was

then connected with horizontal curves. The lengths and radii of these curves was set by safety

standards of the design speed of seventy miles per hour. The highway extension has many

horizontal curves since it goes out of its way to try and not disturb nature and wildlife habitats as

much as possible. Horizontal curves are discussed further in Chapter Two of this report.

The next task at hand for the team was designing vertical curves. Since our highway goes

through mountainous terrain and changes grade and elevation often, it was necessary to make

sure that the ride was as smooth as possible for drivers, as well as safe. In order to ensure this,

fifteen vertical curves were put in place along our highway. In placing these vertical curves, it

was necessary to ensure that they were all contained within horizontal curves for good design

practice and it was necessary to make sure that cut and fill levels of earthwork were relatively

even. More about the vertical curves in the highway extension can be found in Chapter Three of

this report.

Superelevation is an extremely important factor in ensuring the safety of drivers along the

highway. Banked roads help make horizontal curves more safe by reducing sliding friction. This

is especially important since the highway design speed is relatively high. Because of the need for

superelevated roads, much time and care was put into calculating superelevation transition

lengths of the important stations along our curves. The full list of superelevation transition

calculations can be found in Chapter Four of this report.

The last step in the design of our highway was choosing the proper pavement design.

Several different combinations of materials were available for selection, but it was important to

choose the right combination that had the least cost. All thicknesses were calculated from

AASHTO safety standards and all prices were calculated from those given in the project

description. A more detailed description of the pavement design chosen for the freeway

extension is given in Chapter Five of this report.

In the end, through the careful planning of the highway extension, construction time and

cost were minimized, while safety and environmental protection were maximized.

2

Table of Contents Page number

Chapter1: Overview of Design

Section 1.1: Summary……………………………………………………………. 3

Section 1.2: Alternate Designs…………………………………………………… 4

Section 1.3: Selection of Optimal Design………………………………………... 4

Chapter 2: Horizontal Alignment

Section 2.1: Design Criteria…………………………………………………….... 5

Section 2.2: Design Methodology……………………………………………...… 5

Section 2.3: Summary Table………………………………………………...…… 6

Chapter 3: Vertical Alignment

Section 3.1: Design Criteria………………………………………………………. 7

Section 3.2: Design Methodology……………………………………………........ 8

Section 3.3: Summary Table……………………………………………………… 8

Chapter 4: Superelevation Runoff

Section 4.1: Selection and required lengths…………………………………….…. 9

Section 4.2 Summary Tables………………………………………………….…... 9

Chapter 5: Pavement Design

Section 5.1: Optimal Design…………………………………………………....… 14

Section 5.2: Summary Tables…………………………………………………...... 15

Appendices:

A1: Plan and Profile Views of Horizontal and Vertical Curves………………….. 16

A2: Sample Calculations………………………………………………………….. 46

3

Chapter 1: Overview of Design

Section 1.1 Summary:

In order to produce a proper highway design that would join the CA-241 and SR-74

corridors, many factors were taken into consideration. In order to reach our goal, it was

necessary to follow all Caltrans design standards and the AASHTO pavement design method.

Here we highlight some key points of the project design including components and

characteristics of the project that are vital in many, if not all, areas of the design process. A

simple, yet critical factor was the design speed of 70 miles per hour, which determined many

design features from the early stages of the project. Also, the project’s region, residing in a rural

and mountainous area, constantly changing in elevation, also dictated certain components due to

design standards. Another factor taken into consideration was the fact that the highway only

consists of two lanes, with lane widths of 12 feet and shoulder widths of 8 feet. These basic, yet

crucial, elements of the project gave us the fundamental standard to start with and allowed us to

go forth in producing a proper design.

The production of the horizontal alignment involved the implementation of tangent paths,

with minimum elevation changes using the given topographic map. The starting and ending

points match the latitude, longitude, and elevation given as well. Once completing tangent lines,

circular curves are used to connect the tangents. These circular curves follow the Caltrans

standard radii from its design speed in the Caltrans Design Manual (Table 203).

Following the creation of the horizontal alignment, the vertical alignment was created

following Caltrans design standards, taking into consideration factors such as maximum and

minimum grades for rolling terrain (Table 204.3), the algebraic grade differences (Section

204.4), Sight Distance standards (Table 201.1), and minimum curve lengths (Figure 201.4 and

201.5) depending on tangents created. Also, the design is congruent with the initial and final

grade at the BP and EP specified by the project description while crest curves length exceeding

more than half a mile were avoided. We also made sure to practice good design form by keeping

all vertical curves within horizontal curves.

In designing the superelevation runoff of the highway, we made certain to meet

AASHTO minimum standards, selecting the appropriate superelevation for the horizontal curves

from the Caltrans design manual from Table 202.2. Once the proper superelevation rate was

chosen, the proper crown runoff and superelevation runoff lengths were chosen from Figure

202.5A on superelevation transition.

Finally, considering the pavement design, we chose an optimal design following

AASHTO flexible pavement design methods and AASHTO’s standards for minimum thickness

for each layer of pavement found in the project description. We compared the cost estimate for

each design option to find the minimal pavement cost in order to efficiently execute this project.

4

Section 1.2 Alternate Designs:

While producing this project, two different sets of alignments were constructed with

varying design elements. By comparison, we were able to implement transportation engineering

judgment in order to choose between the more superior of the two possible plans.

The first of the two possible highway design options, Design A, had a total length of

27,262 feet. It contained 22 horizontal curves and 14 vertical curves. This particular design was

comprised mostly of earthwork area which needed to be filled that was much greater than the

amount of cut needed.

In comparison to the first possible design, the second design option, Design B, features a

total design length of 26,883 feet. It consists of 11 horizontal curves and 15 vertical curves. This

design provided more evenly distributed areas of cut and fill, which in nature is more efficient in

overall project production, as it not only is beneficial to the budget, but also time spent in

constructing the highway.

Section 1.3 Selection of Optimal Design:

The optimal design between the two choices, we felt, was Design B. The cost of

construction in Design A would be greater than that of the latter design, due to the fact that its

length is greater than that of Design B. Also, the fact that Design A has many horizontal curves

contributes to why it is not the primary choice in design, as having a minimal amount of curves

provides a more aesthetically pleasing environment for drivers. In addition, the overall grade

change of design A was more than the grade change produced in Design B, which contains

smoother transitions in the elevation change throughout the alignment.

In consideration of the earthwork involved in the project, it costs more to seek out soil

from other locations than to use the cut area of soil from the same project to fill the necessary

space. Design A requires a significant amount of soil to be filled, which exceeds the amount of

area cut out from the design. This would result in more time and money spent displacing soil in

order to achieve adequate results. In comparison, Design B allows for cut soil from this project to

be transported to areas close by needing to be filled, which in nature is more efficient in

earthwork costs and time spent on cut and fill.

The final factor in the decision to choose Design B, was that the initial and final grades

and elevation of Design A did not correspond to that of the project description. In Design A, the

end point elevation is not the specified elevation in the provided project description and the final

grade of +3.0% did not agree as well. Though Design A did not meet the required grades and

elevation, Design B executes these necessary factors in designing the projected highway.

5

Chapter 2: Horizontal Alignment

Section 2.1 Design Criteria:

This section outlines the design standards followed in creating the highway’s horizontal

alignment. The focus of the highway was to keep the road on the same contour line, in order to

keep the elevation difference to an absolute minimum to keep cost low. As a part of our public

outreach, the group decided to avoid building too close to a school, Tesoro High School, located

near our starting point. Due to environmental issues, the design also took into account the

location of the Thomas F. Riley Wilderness Park, located east of the planned highway. The last

restricted area was a power plant near the end point of the highway. All precautions were taken

into account and all sensitive sites will not be disturbed by this freeway design. This project

followed its own design standards, in accordance with the standards provided by AASHTO and

Caltrans. Based off of the geometric design Table 203.2 in the Caltrans Design Manual, with a

highway design speed of 70 miles per hour, the horizontal curve’s minimum radius in the

alignment is equivalent to 2,100 feet in addition to a minimum horizontal curve length of 750

feet. This planned horizontal alignment does not implement any broken back, reverse, or

compound horizontal curves.

Section 2.2 Design Methodology:

Several factors were considered in designing the highway’s horizontal alignment:

Follow the Caltrans design standards:

I. A study of the vertical profile of the land before finalizing the design

II. Minimizing cost where applicable without losing any safety factors

III. Avoiding any restricted areas

IV. Following the BP and EP latitude/longitude points given by the project guidelines

V. Keeping all vertical curves within horizontal curves

VI. Exceeding minimum curve radii

The maximum horizontal curve length of 2,100 feet was not exceeded; therefore the

earthwork’s cost was minimized. In general, horizontal curves with bigger curve lengths incur a

greater cost, compared to shorter horizontal curve lengths. Table 1 represents all the information

of the eleven horizontal curves present in our project. It was crucial that our team avoided steep

drops and great inclines in the route, as this would incur great costs by requiring large amounts

of cut and fill. The highway’s horizontal alignment consisted of curves that followed the design

standards for curve radius and length while providing the highest level of safety for the lowest

projected cost.

6

Section 2.3 Summary Table:

Table 1: Horizontal Alignment Summary

HC 7 HC 8 HC 9 HC 10 HC 11

PC [stations] 187+83.48 200+89.38 223+02.04 237+94.36 250+79.05

Elevation-PC [ft] 502.12 486.15 441.12 400.8 346.19

PT [stations] 193+08.37 203+73.26 227+97.25 250+79.05 275+05.63

Elevation-PT [ft] 495.7 481.98 429.11 346.17 260.32

Curve Length [ft] 524.9 283.89 495.22 1284.68 2426.58

Radius [ft] 2100 2100 2100 2100 2100

Central Angle

[degrees]

14.3212 7.7455 13.5114 35.0509 66.2061

Tangent Length

[ft]

263.8246902 142.1602634 248.7632243 663.1531235 1369.132077

Superelevation

Rate [ft/ft]

0.06 0.06 0.06 0.06 0.06

Superelevation

Runoff Length [ft]

150 150 150 150 150

Crown Runoff

Length [ft]

50 50 50 50 50

Superelevation

Transition Length

[ft]

200 200 200 200 200

HC 1 HC 2 HC 3 HC 4 HC 5 HC 6

PC [stations] 25+84.08 30+78.70 58+37.36 84+31.98 108+38.21 141+56.95

Elevation-PC [ft] 687.25 680.16 699.26 685.98 671.41 596.02

PT [stations] 27+43.45 40+51.78 63+78.08 98+60.81 112+08.74 155+65.26

Elevation-PT [ft] 683.81 679.83 702.45 675.62 668.87 555.49

Curve Length

[ft]

159.36 973.08 540.71 1428.83 370.53 1408.32

Radius [ft] 2100 2100 2100 2100 2100 2100

Central Angle

[degrees]

4.348 26.5491 14.7526 38.9837 10.1094 38.4241

Tangent Length

[ft]

79.7195229 495.4341518 271.8591243 743.3128475 185.7465682 731.7926234

Superelevation

Rate [ft/ft]

0.06 0.06 0.06 0.06 0.06 0.06

Superelevation

Runoff Length

[ft]

150 150 150 150 150 150

Crown Runoff

Length [ft]

50 50 50 50 50 50

Superelevation

Transition

Length [ft]

200 200 200 200 200 200

7

Chapter 3: Vertical Alignment

Section 3.1 Design Criteria:

In this project were able to designate vertical curves which coincide with standards of

both the given project as well as the corresponding rules and regulations specified in the Caltrans

Highway Design Manual. In designing these Vertical curves, grade standards were kept in mind.

Referencing to Table 204.3, which provides the maximum grades for various forms of terrain

and highways, the corresponding grade for rolling terrain is 5%. This was the maximum grade

that was allowable in the project which was not exceeded. Also, the minimum grade of 0.3% was

met, also mentioned in Table 204.3.

An important factor in geometric design standards is sight distance, consisting of both

Stopping Sight Distance and Passing Sight Distance. The Caltrans Highway Design Manual

provides Table 201.1: Sight Distance Standards which gives a list of design speeds and their

corresponding stopping sight distances and passing sight distances in accordance with

AASHTO’s standards. With a design speed of 70 mph, the corresponding stopping sight distance

and passing sight distance are 750 ft and 2,500 ft, respectively. The consideration of the passing

sight distance is particularly important in this two lane design, for section 201.2 highlights that

only in 2-lane roads would there be consideration of a passing sight distance.

Various factors are taken into consideration when designing vertical curves, including

curve length as well as sight distance which may be considered further. In order to consider the

proper curve lengths and stopping sight distance on crest vertical curves, Figure 201.4 was

utilized to take the correct precautions. It provides two equations which factor in sight distance,

curve length, and algebraic grade difference which provides us with proper curve length. Crest

curve lengths exceeding more than half a mile were avoided, following standards. Also, the

Figure 201.5 provides proper stopping sight distance on sag vertical curves and also provides a

reference for proper curve length based on specified design speeds. There are two unique

equations to sag vertical curves relating the curve length, sight distance, and algebraic grade

difference for each curve. Sample calculations for both crest and sag curves are provided;

however, one must also consider the minimum curve lengths specified in the manual.

Due to standards, specified in Section 204.4 of the manual, an algebraic grade difference

between initial and final grades of less than 2% has a corresponding minimum vertical curve

length of 200 feet. Also, in this section is a reference to minimum curve lengths in situations

where the grade difference is greater than 2 percent and with a design speed exceeding 40 miles

per hour, stating that in such situations the minimum length of the vertical curve would be 10

times the velocity. With a design speed of 70 miles per hour, the minimum vertical curve length

is 700 ft, which would override the sample calculations of curve lengths below this number. This

condition was applied to several curves as the grade difference and design speed satisfies the

requirements. Overall, the vertical alignment design was created accurately, following standards,

and agrees with the beginning and end points, as specified in the project description.

8

Section 3.2 Design Methodology:

Using the proper minimum grades and minimum vertical curve lengths, we were able to

produce a design that coincides with the Caltrans safety standards. However, this project enabled

us to practice our personal opinions as transportation engineers on design as well, particularly in

terms of earthwork. As previously mentioned, we chose a design which resulted in more evenly

distributed volume between cut and fill, which would reduce both time and monetary needs to

conclude the project. Though we used more Vertical Curves than initially intended with the

previous design, we were able to reach our goal of a more efficient project result in earthwork.

Also, we hoped to produce a corridor path that would be both aesthetically pleasing and

safe for drivers. The given project, in nature, was a challenge in producing a design in such a

terrain as the Coto de Caza mountainous area, with large elevation differences. However, we

were able to design this project under such conditions while following proper Caltrans standards.

Overall, as section 204.4 in Caltrans manual states, correctly designed vertical curves

should provide safety, comfortable driving, proper drainage, adequate sight distance, and be

aesthetically pleasing. We believe that we have complied with all of the above.

Section 3.3: Summary Table

Table 2: Vertical Alignment Summary

VC 1 VC 2 VC 3 VC 4 VC 5 VC 6 VC 7 VC 8

PVC [Stations] 26+81.74 34+91.00 44+76.55 60+00.00 70+10.75 80+85.46 121+50.00 146+64.20

PVT [Stations] 28+81.74 36+91.00 46+76.55 62+00.00 72+10.75 82+85.46 128+50.00 148+64.20

Curve Length

[ft]

200 200 200 200 200 200 700 200

Initial Grade

[%]

-2.5 -0.72 0.73 1.24 0.3 -1.25 -0.69 -3.86

Final Grade [%] -0.72 0.73 1.24 0.3 -1.25 -0.39 -3.86 -2.13

Grade

Difference

1.78 1.45 0.51 0.94 1.55 0.86 3.17 1.73

Min. Length of

Curve [ft]

200 200 200 200 200 200 700 200

VC 9 VC 10 VC 11 VC 12 VC 13 VC 14 VC 15

PVC [Stations] 170+00.00 202+21.65 224+94.09 238+42.62 255+85.69 273+56.08 285+52.07

PVT [Stations] 172+00.00 204+21.65 226+94.09 245+42.62 257+85.69 280+56.08 287+52.07

Curve Length [ft] 200 200 200 700 200 700 200

Initial Grade [%] -2.13 -1.22 -2.13 -2.84 -4.88 -3.12 0.06

Final Grade [%] -1.22 -2.13 -2.84 -4.88 -3.12 0.06 3

Grade Difference 0.91 0.91 0.71 2.04 1.76 3.18 2.94

Min. Length of

Curve [ft]

200 200 200 700 200 700 200

9

Chapter 4: Superelevation Runoff

Section 4.1 Selection and required lengths:

For this highway design there are 11 horizontal curves, all with equal radii of 2100 feet.

Referencing to the Table 202.2 in the Caltrans Design Manual, for a 2-lane conventional

highway with a curve radii between 1900 and 2199 feet, will have a superelevation of 0.06 feet

per foot when the curve is in full superelevation. Therefore all of the horizontal curves’

superelevation runoff lengths are the same and have a value of 150 feet. The curves also all have

the same crown runoff lengths of 50 feet, as well as a normal crown of 2% and a shoulder cross

slope of 5%. Curves were designed with minimum lengths to ensure that the requirements for

driver safety and comfort are achieved.

Section 4.2 Summary Table

Table 3: Superelevation Transition Summary

Left Centerline Right

Stations Shoulder

Elevation

Shoulder

Offset

Pavement

Elevation

Offset Elevation Offset Pavement

Elevation

Shoulder

Offset

Shoulder

Elevation

Curve

1

North

End

1 23+50.75 -0.64 -0.24 -0.24 -0.64

2 24+34.08 691.01 -0.24 691.01 -0.24 691.25 -0.24 691.01 -0.64 690.61

3 24+84.08 690 0 690 0 690 -0.24 689.76 -0.64 689.36

4 25+34.05 688.99 0.24 688.99 0.24 688.75 -0.24 688.51 -0.64 688.11

PC 25+84.08 687.73 0.48 687.73 0.48 687.25 -0.48 686.77 -0.64 686.61

6 26+34.08 686.97 0.72 686.97 0.72 686.25 -0.72 685.53 -0.72 685.53

South

End

6' 26+93.45 685.29 0.72 685.29 0.72 684.57 -0.72 683.85 -0.72 683.85

PT 27+43.45 684.01 0.48 684.01 0.48 683.53 -0.48 683.05 -0.64 682.89

4' 27+93.45 682.78 0.24 682.78 0.24 682.54 -0.24 682.3 -0.64 681.9

3' 28+43.45 682.01 0 682.01 0 682.01 -0.24 681.77 -0.64 681.37

2' 28+93.45 681.21 -0.24 681.21 -0.24 681.45 -0.24 681.21 -0.64 680.81

1' 29+46.78 680.43 -0.64 680.83 -0.24 681.07 -0.24 680.83 -0.64 680.43

Curve

2

North

End

1 28+45.37 680.94 -0.64 681.34 -0.24 681.58 -0.24 681.34 -0.64 680.94

2 29+28.70 681 -0.24 681 -0.24 681.24 -0.24 681 -0.64 680.6

3 29+78.70 680.87 0 680.87 0 680.87 -0.24 680.63 -0.64 680.23

4 30+28.70 680.76 0.24 680.76 0.24 680.52 -0.24 680.28 -0.64 679.88

PC 30+78.70 680.64 0.48 680.64 0.48 680.16 -0.48 679.68 -0.64 679.52

South

End

6 31+28.7 680.5 0.72 680.5 0.72 679.78 -0.72 679.06 -0.72 679.06

10

6' 40+01.78 680.18 0.72 680.18 0.72 679.46 -0.72 678.74 -0.72 678.74

PT 40+51.78 680.31 0.48 680.31 0.48 679.83 -0.48 679.35 -0.64 679.19

4' 41+01.78 680.43 0.24 680.43 0.24 680.19 -0.24 679.95 -0.64 679.55

3' 41+51.78 681.56 0 681.56 0 681.56 -0.24 681.32 -0.64 680.92

2' 42+01.78 680.7 -0.24 680.7 -0.24 680.94 -0.24 680.7 -0.64 680.3

1' 42+85.11 680.88 -0.64 681.28 -0.24 681.52 -0.24 681.28 681.52

Curve

3

North

End

1 56+04.03 695.71 -0.64 696.11 -0.24 696.35 -0.24 696.11 -0.64 695.71

2 56+87.36 696.77 -0.64 697.17 -0.24 697.41 -0.24 697.17 -0.24 697.17

3 57+37.36 697.4 -0.64 697.8 -0.24 698.04 0 698.04 0 698.04

4 57+87.36 698.04 -0.64 698.44 -0.24 698.68 0.24 698.92 0.24 698.92

PC 58+37.36 698.62 -0.64 698.78 -0.48 699.26 0.48 699.74 0.48 699.74

6 58+87.36 699.17 -0.72 699.17 -0.72 699.89 0.72 700.61 0.72 700.61

South

End

6' 63+28.08 -0.72 -0.72 -0.72 -0.72 0.72 0.72 0.72 0.72

PT 63+78.08 701.81 -0.64 701.97 -0.48 702.45 0.48 702.93 0.48 702.93

4' 64+28.08 701.84 -0.64 702.24 -0.24 702.48 0.24 702.72 0.24 702.72

3' 64+78.08 701.86 -0.64 702.26 -0.24 702.5 0 702.5 0 702.5

2' 65+28.08 701.88 -0.64 702.28 -0.24 702.52 -0.24 702.28 -0.24 702.28

1' 66+11.41 701.88 -0.64 702.28 -0.24 702.52 -0.24 702.28 -0.64 701.88

Curve

4

North

End

1 81+98.65 688.22 -0.64 688.62 -0.24 688.86 -0.24 688.62 -0.64 688.22

2 82+81.98 687.2 -0.64 687.6 -0.24 687.84 -0.24 687.6 -0.24 687.6

3 83+31.98 686.6 -0.64 687 -0.24 687.24 0 687.24 0 687.24

4 83+81.98 685.33 -0.64 685.73 -0.24 685.97 0.24 686.21 0.24 686.21

PC 84+31.98 685.34 -0.64 685.5 -0.48 685.98 0.48 686.46 0.48 686.46

6 84+81.98 684.62 -0.72 684.62 -0.72 685.34 0.72 686.06 0.72 686.06

South

End

6' 98+10.81 685.13 -0.72 685.13 -0.72 685.85 0.72 686.57 0.72 686.57

PT 98+60.81 674.98 -0.64 675.14 -0.48 675.62 0.48 676.1 0.48 676.1

4' 99+10.81 674.8 -0.64 675.2 -0.24 675.44 0.24 675.68 0.24 675.68

3' 99+60.81 674.58 -0.64 674.98 -0.24 675.22 0 675.22 0 675.22

2' 100+10.81 674.36 -0.64 674.76 -0.24 675 -0.24 674.76 -0.24 674.76

1' 100+94.14 674.05 -0.64 674.45 -0.24 674.69 -0.24 674.45 -0.64 674.05

Curve

5

North

End

1 106+04.88 672.11 -0.64 672.51 -0.24 672.75 -0.24 672.51 -0.64 672.11

2 106+88.21 671.94 -0.24 671.94 -0.24 672.18 -0.24 671.94 -0.64 671.54

11

3 107+38.21 671.83 0 671.83 0 671.83 -0.24 671.59 -0.64 671.19

4 107+88.21 671.73 0.24 671.73 0.24 671.49 -0.24 671.25 -0.64 670.85

PC 108+38.21 671.89 0.48 671.89 0.48 671.41 -0.48 670.93 -0.64 670.77

6 108+88.21 671.72 0.72 671.72 0.72 671 -0.72 670.28 -0.72 670.28

South

End

6' 111+58.74 669.94 0.72 669.94 0.72 669.22 -0.72 668.5 -0.72 668.5

PT 112+08.74 669.35 0.48 669.35 0.48 668.87 -0.48 668.39 -0.64 668.23

4' 112+58.74 668.76 0.24 668.76 0.24 668.52 -0.24 668.28 -0.64 667.88

3' 113+08.74 667.98 0 667.98 0 667.98 -0.24 667.74 -0.64 667.34

2' 113+58.74 667.61 -0.24 667.61 -0.24 667.85 -0.24 667.61 -0.64 667.21

1' 114+42.07 666.65 -0.64 667.05 -0.24 667.29 -0.24 667.05 667.29

Curve

6

North

End

1 139+23.62 604.39 -0.64 604.79 -0.24 605.03 -0.24 604.79 -0.64 604.39

2 140+06.95 601.57 -0.24 601.57 -0.24 601.81 -0.24 601.57 -0.64 601.17

3 140+56.95 599.88 0 599.88 0 599.88 -0.24 599.64 -0.64 599.24

4 141+06.95 598.19 0.24 598.19 0.24 597.95 -0.24 597.71 -0.64 597.31

PC 141+56.95 596.5 0.48 596.5 0.48 596.02 -0.48 595.54 -0.64 595.38

6 142+06.95 594.85 0.72 594.85 0.72 594.13 -0.72 593.41 -0.72 593.41

South

End

6' 155+15.26 557.29 0.72 557.29 0.72 556.57 -0.72 555.85 -0.72 555.85

PT 155+65.26 555.97 0.48 555.97 0.48 555.49 -0.48 555.01 -0.64 554.85

4' 156+15.26 554.68 0.24 554.68 0.24 554.44 -0.24 554.2 -0.64 553.8

3' 156+65.26 553.38 0 553.38 0 553.38 -0.24 553.14 -0.64 552.74

2' 157+15.26 552.07 -0.24 552.07 -0.24 552.31 -0.24 552.07 -0.64 551.67

1' 157+98.59 551.56 -0.64 551.96 -0.24 552.2 -0.24 551.96 -0.64 551.56

12

Curve

7

North

End

1 185+50.15 504.33 -0.64 504.73 -0.24 504.97 -0.24 504.73 -0.64 504.33

2 186+33.48 503.71 -0.24 503.71 -0.24 503.95 -0.24 503.71 -0.64 503.31

3 186+83.48 503.34 0 503.34 0 503.34 -0.24 503.1 -0.64 502.7

4 187+33.48 502.97 0.24 502.97 0.24 502.73 -0.24 502.49 -0.64 502.09

PC 187+83.48 502.6 0.48 502.6 0.48 502.12 -0.48 501.64 -0.64 501.48

6 188+33.48 502.22 0.72 502.22 0.72 501.5 -0.72 500.78 -0.72 500.78

South

End

6' 192+58.37 497.03 0.72 497.03 0.72 496.31 -0.72 495.59 -0.72 495.59

PT 193+08.37 495.57 0.48 495.57 0.48 495.09 -0.48 494.61 -0.64 494.45

4' 193+58.37 494.72 0.24 494.72 0.24 494.48 -0.24 494.24 -0.64 493.84

3' 194+08.37 493.87 0 493.87 0 493.87 -0.24 493.63 -0.64 493.23

2' 194+58.37 493.02 -0.24 493.02 -0.24 493.26 -0.24 493.02 -0.64 492.62

1' 195+41.67 491.6 -0.64 492 -0.24 492.24 -0.24 492 -0.64 491.6

Curve

8

North

End

1 198+56.06 488.36 -0.64 488.76 -0.24 489 -0.24 488.76 -0.64 488.36

2 199+39.38 487.34 -0.64 487.74 -0.24 487.98 -0.24 487.74 -0.24 487.74

3 199+89.38 486.73 -0.64 487.13 -0.24 487.37 0 487.37 0 487.37

4 200+39.38 486.12 -0.64 486.52 -0.24 486.76 0.24 487 0.24 487

PC 200+89.38 485.51 -0.64 485.67 -0.48 486.15 0.48 486.63 0.48 486.63

6 201+39.38 484.82 -0.72 484.82 -0.72 485.54 0.72 486.26 0.72 486.26

South

End

6' 203+23.26 452.1 -0.72 452.1 -0.72 452.82 0.72 453.54 0.72 453.54

PT 203+73.26 481.34 -0.64 481.5 -0.48 481.98 0.48 482.46 0.48 482.46

4' 204+23.26 480.5 -0.64 480.9 -0.24 481.14 0.24 481.38 0.24 481.38

3' 204+73.26 479.43 -0.64 479.83 -0.24 480.07 0 480.07 0 480.07

2' 205+23.26 478.37 -0.64 478.77 -0.24 479.01 -0.24 478.77 -0.24 478.77

1' 206+06.59 476.59 -0.64 476.99 -0.24 477.23 -0.24 476.99 -0.64 476.59

Curve

9

North

End

1 220+68.71 445.36 -0.64 445.76 -0.24 446 -0.24 445.76 -0.64 445.36

2 221+52.04 443.58 -0.64 443.98 -0.24 444.22 -0.24 443.98 -0.24 443.98

3 222+02.04 442.52 -0.64 442.92 -0.24 443.16 0 443.16 0 443.16

4 222+52.04 441.51 -0.64 441.91 -0.24 442.15 0.24 442.39 0.24 442.39

PC 223+02.04 440.48 -0.64 440.64 -0.48 441.12 0.48 441.6 0.48 441.6

6 223+52.04 439.32 -0.72 439.32 -0.72 440.04 0.72 440.76 0.72 440.76

South

End

6' 227+47.25 429.81 -0.72 429.81 -0.72 430.53 0.72 431.25 0.72 431.25

PT 227+97.25 428.47 -0.64 428.63 -0.48 429.11 0.48 429.59 0.48 429.59

4' 228+47.25 427.06 -0.64 427.46 -0.24 427.7 0.24 427.94 0.24 427.94

13

3' 228+97.25 425.63 -0.64 426.03 -0.24 426.27 0 426.27 0 426.27

2' 229+47.25 424.21 -0.64 424.61 -0.24 424.85 -0.24 424.61 -0.24 424.61

1' 230+30.58 421.84 -0.64 422.24 -0.24 422.48 -0.24 422.24 -0.64 421.84

Curve

10

North

End

1 235+61.03 406.74 -0.64 407.14 -0.24 407.38 -0.24 407.14 -0.64 406.74

2 236+44.36 404.37 -0.64 404.77 -0.24 405.01 -0.24 404.77 -0.24 404.77

3 236+94.36 402.95 -0.64 403.35 -0.24 403.59 0 403.59 0 403.59

4 237+44.36 401.53 -0.64 401.93 -0.24 402.17 0.24 402.41 0.24 402.41

PC 237+94.36 400.16 -0.64 400.32 -0.48 400.8 0.48 401.28 0.48 401.28

6 238+44.36 398.61 -0.72 398.61 -0.72 399.33 0.72 400.05 0.72 400.05

South

End

6' 250+29.05 347.9 -0.72 347.9 -0.72 348.62 0.72 349.34 0.72 349.34

PT 250+79.05 345.53 -0.64 345.69 -0.48 346.17 0.48 346.65 0.48 346.65

4' 251+29.05 343.09 -0.64 343.49 -0.24 343.73 0.24 343.97 0.24 343.97

3' 251+79.05 340.65 -0.64 341.05 -0.24 341.29 0 341.29 0 341.29

2' 252+29.05 338.21 -0.64 338.61 -0.24 338.85 -0.24 338.61 -0.24 338.61

1' 253+12.38 334.14 -0.64 334.54 -0.24 334.78 -0.24 334.54 -0.64 334.14

Curve

11

North

End

1 248+45.72 356.92 -0.64 357.32 -0.24 357.56 -0.24 357.32 -0.64 356.92

2 249+29.05 353.26 -0.24 353.26 -0.24 353.5 -0.24 353.26 -0.64 352.86

3 249+79.05 351.06 0 351.06 0 351.06 -0.24 350.82 -0.64 350.42

4 250+29.05 348.86 0.24 348.86 0.24 348.62 -0.24 348.38 -0.64 347.98

PC 250+79.05 346.67 0.48 346.67 0.48 346.19 -0.48 345.71 -0.64 345.55

6 251+29.05 344.45 0.72 344.45 0.72 343.73 -0.72 343.01 -0.72 343.01

South

End

6' 274+55.63 262.43 0.72 262.43 0.72 261.71 -0.72 260.99 -0.72 260.99

PT 275+05.63 260.8 0.48 260.8 0.48 260.32 -0.48 259.84 -0.64 259.68

4' 275+55.63 259.42 0.24 259.42 0.24 259.18 -0.24 258.94 -0.64 258.54

3' 276+05.63 258.21 0 258.21 0 258.21 -0.24 257.97 -0.64 257.57

2' 276+55.63 257 -0.24 257 -0.24 257.24 -0.24 257 -0.64 256.6

1' 277+38.96 255.26 -0.64 255.66 -0.24 255.9 -0.24 255.66 -0.64 255.26

14

Chapter 5: Pavement Design

Section 5.1 Optimal Design:

The pavement of the highway extension was designed using the AASHTO Flexible

Pavement Design Method. The cross section of the pavement design chosen, design #2, is shown

in the picture below. The surface course is made up of 5.7 inches of plant mix asphalt, with a 6

inch, cement treated base course and a 6 inch sandy clay subbase course. The objective was to

keep the cost for pavement construction as low as possible. This particular design was chosen as

the optimal design because it meets all the standards for safety and is the most affordable of all

three alternative designs. About 9,000 vehicles utilize the highway each day per lane, but only

about 720 of these vehicles are trucks that cause significant damage to the pavement over time.

The thicknesses of each section of the pavement are based on the daily axle loading of the trucks

assuming that the structural number was 4 and checking this assumption with the AASHTO

Nomograph. Because of the small percentage of trucks on the highway, it was okay to stick with

the minimum allowable thickness for the subbase layer when designing the pavement. The cost

to construct each layer of the pavement was based on the cost per volume of its individual

material. Volumes were computed from the thickness of each layer, the width of the highway

(12.2m), and the length of the entire stretch of highway (8,193.6m).

Figure 1: Cross Section of Optimal Pavement Design

15

Section 5.2 Summary:

Table 4: Pavement Design Summaries

Design #1

Materials Thickness Cost

Road Mix 17” $6,474,534

Sandy Gravel 5.5” $698,234

Sandy Clay 6” $837,881

Total Cost: $8,010,649

Design #2

Materials Thickness Cost

Plant Mix 5.7” $2,894,497

Cement treatment 6” $1,371,078

Sandy Clay 6” $837,881

Total Cost: $5,103,456

Design #3

Materials Thickness Cost

Plant Mix 7.4” $3,757,768

Crushed stone 4.2” $799,795

Sandy Clay 6” $837,881

Total Cost: $5,395,444