Highway Design Training Course Part I

Highway Design Training Course Part I
By Xudong Jia, Ph.D., PE Timothy Romine Department of Civil Engineering California State Polytechnic University, Pomona Case Study March 2012

Training Project

Structure of Training Workshop
Fundamentals of Highway Design Chapter 1 Introduction Chapter 2 CalTrans Highway Design Process Chapter 3 Design Controls and Criteria Chapter 4 Project Description Chapter 5 Horizontal Alignments Chapter 6 Profiles and Vertical Alignments Chapter 7 Cross Section design and Earthwork Chapter 8 Roadside Design Chapter 9 Conclusions

CalTrans Project Development Process
CalTrans project development process is described in the CalTrans Project Development Procedures Manual. It is tied to the legal requirements of environmental laws and regulations, engineering requirements, and CalTrans’ management approval steps. The process is depicted by a milestone chart. This chart is very important for any civil engineers who are involved in a CalTrans project from its feasibility study to the completion of construction.

System and Regional System Planning TIP Program 0. Identify Project Need Prepare a 2- or 3-page Project Proposal Report Assign a Project Manager (PM) Form a Project Development Team (PDT) PM prepares a Project Work Plan Project Initiation A

Determine Project Alternatives including no-built; Document the alternatives in Project Study Report; Approve PSR 10. Approve PSR Initiate Environmental Studies Initiate DPR & DED Circulate DPR&DED in dist. Circulate DED/Approve DPR Feasibility study of all the alternatives Listed in the PSR. Two major studies: Environmental Studies (Draft Env. Document) Engineering Studies (Draft Project Report) The Least environmentally damaging, practicable alternative (LEDPA) must be identified. B

B Conduct a public hearing; Collect comments and insert them in the analysis of the preferred alternative; Approve final environmental document; Approve the preferred project alternative Public Hearing 160. Approve FED Initiate project design to prepare Plans, Specifications and Estimate (PS&E) An environmental reevaluation is undertaken Structure PS &E and R/W mapping start concurrently with the project PS &E. Initiate PS & E (200); Geo Base Map (220); Skeleton Layout (260) C

Conduct a detailed project design on plans, quantity calculations and contract specifications; Circulate project plans : Detailed Project Design Insert the comments in the PS&E design Conduct a Safety Review Finalize PS &E Submit Project PS7E with Structure PS&E to the Office of Office Engineer of the Engineering Service Center 300 – 380: Complete Project Design D

The design work now is complete; Right of Way Certification; Funds Request Approval; Assemble the final Project documents and bidding package; Open bids and Award a contract : Prepare and Advertise Project Contract Start and finish construction according PS&E Prepare final project file : Conduct and Complete Construction Project

Key Terms and Concepts Before we start, the following key terms should be clarified: 1. ADT 2. Overcross and Undercross 3. Bridges and Culverts 4. 2-lane, 4-lane, 6-lane, 8-lane highways 5. Elements of a typical road cross section 6. Highway stationing 7. Mandatory, Advisory, and Permissive Standards

ADT Number of vehicles that pass a particular point on a roadway during a period of 24 consecutive hours averaged over a design year.

ADT What is the Unit of ADT?
Measured on One Direction or Two Directions of the road ? Present ADT is used for Resurfacing, Restoration, and Rehabilitation (RRR) projects. Future ADT is used for new construction projects. How to estimate present ADT? How to Define Future? How to estimate future ADT?

Overcross or Undercross
Adopted from

Bridges and Culverts Structures whose span > 6.1 m
are bridges. Structure Engineers are responsible for their design. Structure whose span <= 6.1 m are culverts. Highway Designers are responsible for their design

2-Lane, 4-lane, 6-lane and 8-Lane Highways

Divided and Undivided Highways
Separated roadbeds for traffic in opposite directions One Centerline and two station lines Superelevation are designed independently for curves in opposite directions Undivided Highways One roadbed for traffic in opposite directions One Centerline and One Station Line Superelevation is designed jointly for curves

Elements of a Typical Road Cross Section

Highway Stationing Stationing goes from West to East for even-number highways Stationing goes from North to South for odd-number highways Ramps associated with even-number highways are stationed from West to East. Ramps associated with odd-number highways are stationed from North to South.

Mandatory, Advisory, and Permissive
Mandatory standards are most essential to achievement of overall design objectives. Mandatory standards use the word "shall" and are printed in Boldface type. Advisory standards are important also, but allow greater flexibility in application to accommodate design constraints. Advisory standards use the word "should" and are indicated by Underlining. Permissive Standards are all standards other than mandatory or advisory, whether indicated by the use of "should" or "may“. They are permissive with no requirement for application intended.

Design Manuals Design Manuals often used in a highway project:
CalTrans Project Development Procedures Manual CalTrans HDM AASHTO Green Book Ramp Meter Design Manual AASHTO Roadside Design Guide CalTrans Flexible Pavement Rehabilitation Manual Traffic Manual CAD User Manual Highway Capacity Manual

Design Controls and Criteria
Design Controls and Criteria consist of general controls and detailed controls that are related to elements of a highway design project General Controls are Represented by the Design Designation listed in PSR and PS documents. They are ADT, DHV, D,T, and V. Detailed Controls vary from a project to another. An example control is Vertical Clearance that should be considered when undercrossing or overcrossing structures are involved.

General Design Controls and Criteria
Present ADT Current ADT DHV T V Design LOS

DHV What is the Unit of DHV?
Measured on One Direction or Two Directions of the road ? Present DHV is used for Resurfacing, Restoration, and Rehabilitation (RRR) projects. Future DHV is used for new construction projects.

How to Measure Current DHV

How to Measure Future DHV
K Value = DHV/ADT Kcurrent = Kfuture DHV future = Kcurrent * ADT future

T - Truck Volume Percentage of Trucks present in the traffic flow during the design hour It varies from project to project, normally 5-10% PCE - Passenger Car Equivalent One truck can not considered as one passenger car from the viewpoint of traffic impacts. 1 truck = 4 PCE means that one truck is equivalent to 4 passenger cars Truck volume is primarily collected from HPMS (Highway Performance Monitoring System). Projection of truck volume in future traffic flow Is challenging topic.

V – Design Speed Design speed is selected to establish specific minimum geometric design elements for a particular section of highway It is influenced principally by the character of terrain, economic considerations, environmental factors, type and anticipated volume of traffic, functional classification of the highway, and whether the area is rural or urban. Selection of the design speed for a highway project should follow Table (HDM Page 100-2) that determines design speed based primarily on the functional class of the highway. This is a mandatory requirement.

V – Design Speed A freeway design speed is 75 km/h Is it OK?
A conventional highway in rural area is 55km/h Is it OK? Design speed controls every elements of geometric design including widths of pavement and shoulders, horizontal clearances, etc. True or False A best practice in selecting design speed is to choose as high speed as feasible when a minimum design speed is met. The design speed should be same on various segments of a highway. True or False

Design Speed, Post Speed, 85th Percentile Speed
Design speed is "the maximum safe speed that can be maintained over a specified section of highway. Posted speed refers to the maximum speed limit posted on a section of highway using a regulatory sign. It is based primarily upon the 85th percentile speed when adequate speed samples can be secured. The 85th percentile speed is the speed at or below which 85% of drivers are operating their vehicles. Design Speed  Post Speed = 85th Percentile Speed

Design LOS Level of Service A, B, C, D, E, F
Guide for Selection of Design LOS Rural Rolling Rural Mountainous Highway Type Rural Level Urban/ Suburban Freeway Arterial Collector Local B B C C B B C C C C D D D D D D

Determination of Number of Lanes
Why Do We Care about of Number of Lanes? Two Methods are available for the determination of number of lanes HDM Method: Design LOS Peak Hour Traffic Volume (Design Year/Average pvplph) Urban C-E Rural C-D HCM Method

Determination of Number of Lanes
Example 1000 1600 Other Design-Related Data: 10000 K = 13% D = 65% T = 12% Growth = 4% year of base 1200 800 2002 current ADT volumes

Critical Segment: 10000 1000 10000 1600 + 1200 10000 12800 11800 Critical Segment

HDM Method Assume Peak Hourly Volume in HDM means DHV in the design year Design LOS = C Design Year for a new project is 20 years after the completion of the project: Project Finish Year Design Year 22 Future DHV = (1+ 4%) * 13% = 3944 Veh/Hour Future DDHV = 3944 * 0.65 = 2564 Veh/Hour Number of Lanes = 2564 /1400 = 2 Lanes

HCM Method Design LOS = C, Local Commuters, Standard Lane Width,
Design Speed 110 km/h, PCE = 6 Design Year for a new project is 20 years after the completion of the project: Project Finish Year Design Year 22 Future DHV = (12800* * 0.12*6) (1+ 4%) * 13% = 6309 Veh/H Future DDHV = 6309 * 0.65 = 4104 Veh/H Fhv = 1/(1+0.12(6-1)) = 0.625 Number of Lanes = 4104 /(1740* 1*0.625*1) = 4 lanes

Which One is Good? CalTrans Method : 4-Lane Highway
HCM Method: Lane Highway 8-Lane Highway is the choice The impact of tracks and buses in the traffic stream is Significant in the determination of number of lanes.

Training Project B A C Project Area

Training Project Number of Lanes Route 8: 6-Lane Freeway
Ramps: Single-Lane Ramps Laguna Canyon Road 4-Lane Highway Geometric Control Points Pt A. S 70 E, Elev: ft, Grade –1.5% (English) N ft, E ft (English) S 70 E, Elev: m, Grade –1.5% (Metric) N m, E m (Metric) Pt B S 80 E, Elev: ft, Grade –2.0%(English) N ft, E ft (English) S 80 E, Elev: m, Grade –2.0% (Metric) N m, E m (Metric) Pt C N 10 W, Elev: ft, Grade 4% (English) N ft, E ft (English) N 10 W, Elev: m, Grade 4% (Metric) N m, E m (Metric)

Training Project Design Speed: Route 8 110 km/h Ramps 40-80 km/h
Laguna Canyon Road 55 km/h Others: Cut Slope 1.5:1 Fill Slope 2:1 ROW 3 m away from catch points Design Standards CalTrans HDM AASHTO Green Book Acceptable Highway Design Practice

Horizontal Alignment Elements of Horizontal Alignment
CalTrans Standards on Horizontal Alignment CalTrans Standards Used in the Training Project Conformance Check of CalTrans Standards

Horizontal Alignment A horizontal alignment consists of a series of tangent line segments, spirals and circular curves CalTrans does not use spirals at all Tangent line segments are easy to handle. However the circular curves are Not. They affect significantly the safety considerations of a highway project and require a smooth transition from tangent segments. Circular Curve Spiral Tangent Segment

Circular Curve in Horizontal Alignment
PI BC EC R

Superelevation emax and e
Superelevation e is a cross slope to balance the centrifugal force emax is the maximum superelevation rate given a certain highway type. It varies from one highway type to another. For Example, emax = 0.10 for freeways (Page 200-9) e is the superelevation rate used in the design e is determined based on emax and R (Page 200-9) What is a standard superelevation rate of freeways and expressways with a curve radius of 400 m?

What is a standard superelevation rate of freeways and expressways with a curve radius of 400 m? emax = 0.10 from Table Page 200-9 e = 0.09 from Table Page with R = 400 m

Minimum Radius of Circular Curve
Table HDM P200-16 Given emax = 0.10 for freeways (Page 200-9) V = 100 km/h Fs = 0.12 from Page Design Speed Rmin 30 40 50 60 70 80 90 100 110 120 130 40 70 100 150 200 260 320 400 600 900 1200

Superelevation Transition
Superelevation Transition should be at the two ends of a curve It consists of crown runoff and superelevation runoff (See Page ) The superelevation runoff has its two third on the tangent and one third on the curve.

Superelevation Transition (Example)
A 400-meter radius curve is followed by a reversing curve of a 500-meter radius in a 4-lane undivided freeway. The two curves are separated by a tangent line of 100 meters. Does the design conform with the design standards? 500 m 60 m 400 m

Superelevation Transition (Solution)
500 m 60 m 400 m B A Curve: emax = 0.10 e = 0.09 given R = 400 m 2/3 Runoff = 0.67 * 99 = m B Curve: emax = 0.10 e = 0.07 Given R = 500 m 2/3 Runoff = 0.67 * 78 = m 100 m < = m No OK, What do we do now?

If the alignment is designed for 2-lane highways in mountainous terrain, ramps, collector roads, frontage roads, what do we do? Modify the rate of change of cross slope ( 4% per 20 m)

Stopping Sight Distance on Horizontal Curves

SSD on Horizontal Curves (Example)
A horizontal curve with a radius of 400 meters is designed on a two-lane highway that has design speed of 110 km/h. If the highway is flat at the curve section, determine the minimum distance a large McDonald’s billboard can be placed from the center line of the inside lane of the curve, without reducing the required SSD. Assume PIEV time of 2.5 sec and a = 3.4 m/sec2

SSD on Horizontal Curves (Solution)

CalTrans Standards on Horizontal Alignments
Horizontal Alignment should provide at least the minimum SSD for the chosen design speed at all points of the highway Curves should be designed with their radius greater than Rmin. If Rmin cannot provided enough lateral clearance to an obstruction, Figure governs. The Design Speed between successive curves should not more than 15 km/h due to alignment consistency When  < 10°, minimum curve length = 240 m When  < 0.5°, no curve is needed Compound curves should be avoided. Rshorter = 2/3Rlarger when Rshorter  300 m Larger radius curve follows smaller radius curve on 2-lane highway

The connecting tangent on reversing curves should be greater than 2/3 runoff of the first curve and 2/3 runoff of the second curve. If it is not possible, 4% per 20 m governs. A minimum of 120 m should be considered when feasible. Broken back curves are not desirable. Alignment at bridges: superelevation rate on bridge  10% Bridges should be out of 2/3 runoff of the curve at two ends.

Superelevation: 3000 m radius curve, no superelevation is needed Axis of rotation Centerline on undivided highways Left edge of ETW on ramps and f-f connections centerline on divided highways with median width  20 m median edges of traveled way on divided highways with median width > 20 m

Design Procedures of Horizontal Alignment
1. Investigate and assess the characters of the project area 2. Determine individual elements of alignment Curve Design: R min curve length and  Superelevation Runoff Arrange Tangent Segments and Curves Check Conformance to Design Standards Sight Distance

Horizontal Alignments for Training Project
The Training Project involves the design of five horizontal alignments: One for Freeway Four for Ramps

Freeway Horizontal Alignment Design
Two below PIs are given in the training project for the training project: English PI #1 X = ft, Y = ft PI #2 X = ft, Y = ft or Metric PI #1 X = m, Y = m PI #2 X = m, Y = m A and B control points in terms of direction must be considered so that the freeway horizontal alignment is consistent with alignments outside of the project. Live Demo on how to design the horizontal alignment through trial and error efforts

Freeway Horizontal Alignment

Ramps Horizontal Alignment Design
A diamond interchange is proposed for the training project Three below basic elements should be designed for each ramp: Freeway-Ramp Connector Ramp Alignment Ramp-Local Road Connector

Freeway-Ramp Connector Design
Freeway-Ramp Connectors should be designed based on Figure 504.2a, Figure 504.2b, and Figure 504.2C. Figure 504.2a Advisory standard for single-lane ramp entrance. Figure 504.2b Advisory standard for single-lane ramp exit. Figure 504.2c Advisory standard for ramp location on a curve

Single-Lane Ramp Entrance (Figure 504.2A)

Discuss control points in the figure and clarify inlet nose, 2-m and 7-m points When freeway is not on tangent alignment, select radius to approximate same degree of convergence. Live Demo on how to obtain the control points using Microstation

Single-Lane Ramp Exit (Figure 504.2B)

Discuss control points in the figure and clarify exit nose, 2-m and 7-m points, and DL distance. Minimum length between exit nose and end of ramp is 160 m for full stop at end of ramp Live Demo on how to obtain the control points using Microstation

Ramp Location on a Curve (Figure 504.2C)

Standards shown in Figure 504.2C are for both ramp entrances and exits Live Demo on how to draw the figure in Microstation

Ramp Alignment Design Design speed varies along a ramp.
Design speed at the exit nose should be 80 km/h or greater. Design speed at the inlet node should be consistent with approach alignment standards, at least 80 km/h. Design speed at the end of local road should be 40 km/h Ramp length should be greater than the stopping sight distance experienced on the ramp. Appropriate design speed for any intermediate point on the ramp is chosen based on its location in relation to the points of two ends.

Ramp Widening When do we need to widen ramps for trucks?
Ramps with curve radii of 90 m or less (outside ETW) and central angle greater than 60 degrees, the single lane ramp, and the lane furthest to the right should be widened in accordance with Table 504.3A below: Ramp Radius (m) Widening (m) Lane Width (m) < >

Ramp Length, Lane Drop, 1- or 2-lane Ramps
If the length of a single ramp exceeds 300 meters, an additional lane should be provided on the ramp to permit passing maneuvers. If additional lanes are provided near all entrance ramp intersection, the lane drop should be 2/3 WV on the right. When design year estimated volume exceeds 1500 equiv. pc/h, a 2-lane width of ramp should be provided initially.

Ramp-Local Road Connector Design
Factors below should be considered: Sight Distance, Left-Turn movements and their storage requirements, Crossroads gradient at ramp intersections, Proximity of near-by intersections A right-angle intersection is desired to meet the sight distance requirements. What is the minimum angle allowed? At-grade intersection design standards should be followed for the connector design. The ramp intersection capacity analysis should be conducted before the signalization is granted and the phasing is developed.

Angle of Intersection Is the design OK?

Corner Sight Distance Corner Sight Distance (Table 405.1 Page 400-9)
Design Speed CSD CSD = * Vmajor * 7.5 = 83.4 meters = 90 meters

Typical Connector Design

Ramp Setback Where a separate right turn is provided at ramp terminals, no free turn due to concerns of pedestrians. 60 meters should be provided. For left-turn maneuvers from an off-ramp at an unsignalized intersection, the length of crossroads open to view should be 0.278*V*7.5. Ramp setback from an over-crossing structure follows Figure 504.3J.

Ramp Setback (Figure 504.3J)

Ram Terminals and Local Intersections
The minimum distance (curb return to curb return) between ramps intersections and local intersections should be 125 meters, desirable 160 meters When intersections are closely spaced., traffic operations should be applied to examine short weave and storage lengths and signal phasing.

Ramp Intersection Capacity Analysis

Eastbound Off-Ramp Design

Eastbound On-Ramp Design

Westbound Off-Ramp Design

Westbound On-Ramp Design

Highway Design Training Course Part II
By Xudong Jia, Ph.D., PE Timothy Romine Department of Civil Engineering California State Polytechnic University, Pomona March 2012

Profiles and Vertical Alignment
Elements of Profiles and Vertical Alignments CalTrans Standards on Vertical Alignment CalTrans Standards Used in the Training Project Conformance Check of CalTrans Standards

Horizontal Alignment A vertical alignment alignment consists of a series of grade line segments and circular curves Tangent line segments are easy to handle. However the circular curves are Not. They affect significantly the safety considerations of a highway project and require a smooth transition from tangent segments. Circular Curve Spiral Tangent Segment

Circular Curve in Horizontal Alignment
PI BC EC R

Superelevation e is a cross slope to balance the centrifugal force emax is the maximum superelevation rate given a certain highway type. It varies from one highway type to another. For Example, emax = 0.10 for freeways (Page 200-9) e is the superelevation rate used in the design e is determined based on emax and R (Page 200-9) What is a standard superelevation rate of freeways and expressways with a curve radius of 400 m?

What is a standard superelevation rate of freeways and expressways with a curve radius of 400 m? emax = 0.10 from Table Page 200-9 e = 0.09 from Table Page with R = 400 m

Minimum Radius of Circular Curve
Table HDM P200-16 Given emax = 0.10 for freeways (Page 200-9) V = 100 km/h Fs = 0.12 from Page Design Speed Rmin 30 40 50 60 70 80 90 100 110 120 130 40 70 100 150 200 260 320 400 600 900 1200

Superelevation Transition should be at the two ends of a curve It consists of crown runoff and superelevation runoff (See Page ) The superelevation runoff has its two third on the tangent and one third on the curve.

Superelevation Transition (Example)
A 400-meter radius curve is followed by a reversing curve of a 500-meter radius in a 4-lane undivided freeway. The two curves are separated by a tangent line of 100 meters. Does the design conform with the design standards? 500 m 60 m 400 m

500 m 60 m 400 m B A Curve: emax = 0.10 e = 0.09 given R = 400 m 2/3 Runoff = 0.67 * 99 = m B Curve: emax = 0.10 e = 0.07 Given R = 500 m 2/3 Runoff = 0.67 * 78 = m 100 m < = m No OK, What do we do now?

If the alignment is designed for 2-lane highways in mountainous terrain, ramps, collector roads, frontage roads, what do we do? Modify the rate of change of cross slope ( 4% per 20 m)

Stopping Sight Distance on Horizontal Curves

SSD on Horizontal Curves (Example)
A horizontal curve with a radius of 400 meters is designed on a two-lane highway that has design speed of 110 km/h. If the highway is flat at the curve section, determine the minimum distance a large McDonald’s billboard can be placed from the center line of the inside lane of the curve, without reducing the required SSD. Assume PIEV time of 2.5 sec and a = 3.4 m/sec2

SSD on Horizontal Curves (Solution)

Horizontal Alignment should provide at least the minimum SSD for the chosen design speed at all points of the highway Curves should be designed with their radius greater than Rmin. If Rmin cannot provided enough lateral clearance to an obstruction, Figure governs. The Design Speed between successive curves should not more than 15 km/h due to alignment consistency When  < 10°, minimum curve length = 240 m When  < 0.5°, no curve is needed Compound curves should be avoided. Rshorter = 2/3Rlarger when Rshorter  300 m Larger radius curve follows smaller radius curve on 2-lane highway