Introduction to Roadway Design

Transcription

1 Chapter Introduction to Roadway Design 1 This chapter lays the foundation for the Roadway Design course. You examine the roadway design workflow and the completed drawing files and review the project scope, design parameters, and criteria for the roads being designed. Objectives After completing this chapter, you will be able to: Examine the roadway design workflow and the completed drawing files and review the roadway project scope, design parameters, and criteria. 1

2 Lesson: Reviewing Roadway Design Project Data This lesson lays the foundation for the Roadway Design course. You examine the roadway design workflow and the completed drawing files and review the project scope, design parameters, and criteria for roads being designed. The following illustration shows roadway data with proposed changes. Objectives After completing this lesson, you will be able to: Describe roadway design. Explain the project scope and describe the workflow for the sample roadway design project. List the design parameters and criteria for the roadway design project. Examine the completed roadway design project data in a drawing file. 2 Chapter 1: Introduction to Roadway Design

3 About Roadway Design Roadway design must address environmental, social, and regulatory requirements. Environmental requirements include local terrain and climate; social aspects include expected traffic volume, vehicle type, and impact on nearby neighborhoods; and regulatory requirements include those set by federal, state, or municipal government. Definition of Roadway Design Roadway design, as it relates to this course, is the process of creating a three-dimensional engineering model of a roadway that will be used to generate construction plan documents. Design Standards The design standards for a particular project depend upon the type of facility, the nature of the project, and the source of funding. For example, federal-aid projects are funded through the Federal Highway Administration (FHWA). In this course, American Association of State Highway Transportation Officials (AASHTO) design criteria will be followed unless otherwise specified. Safety is a prime consideration in the development of all designs. Engineering analysis and judgment must be used to determine the safety, cost-effectiveness, and social and environmental impacts of the various design elements. Lesson: Reviewing Roadway Design Project Data 3

4 Example The following illustration shows an example of a roadway project. Workflow The workflow for designing a roadway project using Civil 3D generally follows the process outlined in this section. In preparing for designing the roadway project, the project scope should be defined, and design parameters and criteria must be followed. In practice, iterations of the processes outlined in this chapter will likely be required. Good engineering practice involves evaluating the design and making modifications to or fine-tuning it when necessary. Project Scope The project scope defines the extent of work to be performed in the construction of a roadway design project. The scope of work for this project is defined as follows: 4 Chapter 1: Introduction to Roadway Design

5 STH 25 (Construction Limits Sta to ) Sta to Construct a rural four-lane divided roadway with a median ditch. The four-lane divided roadway will tie into an adjacent project south of Sta Sta to Construct a rural four-lane divided to two-lane transition. Southbound lanes will follow the existing two-lane roadway corridor. Sta to Reconstruct an existing rural two-lane roadway to replace the pavement structure, improve safety in the roadway recovery zone, improve ditch drainage capacity, and increase the stopping sight distance on the crest vertical curve south of the Pine Drive intersection. Sta to Rehabilitate an existing rural two-lane roadway to include mill and overlay pavement, improve the superelevation and cross slope of the existing pavement section, remove and replace the shoulder pavement and base course, and improve ditch drainage capacity. Pine Drive (Construction Limits - Sta to 15+00) Sta to Reconstruct the existing rural two-lane roadway to replace the pavement structure, improve safety in the recovery zone, and improve ditch drainage capacity. Pine Drive will tie into an adjacent project west of Sta and east of Sta Sta Reconstruct an intersection to improve the angle of intersection and accommodate turning movements by providing a northbound right turn lane on STH 25 to accommodate eastbound traffic volumes onto Pine Drive. A side road intersection will be removed and its access eliminated. Driveways and their intersections will not be addressed in this project. Roadway Design Workflow The following steps outline workflow for designing roads. 1. Define the coordinate system to be used on project. This system is usually specified by the client and may be changed at a later time during the project. 2. Create and evaluate the topographic base map and existing ground surface. These are generally created from a field or aerial survey. 3. Create and evaluate the existing property boundaries, such as right-of-ways, easements, and property lines. These are generally created from geospatial data, field survey of property irons, and existing right-of-way plat information. 4. Layout, evaluate, and edit the horizontal alignment. 5. Create the proposed pavement and shoulder edges, including the layout of intersections. This is generally done after creating the horizontal alignments. 6. Layout, evaluate, and edit the design profile. 7. Apply superelevation to the horizontal alignment. 8. Review the design considerations. 9. Create reconstructed roadway or mill and overlay roadway assemblies. 10. Create corridor. 11. Create and edit the intersections. 12. View and edit the corridor. 13. Compute the end area volumes. 14. Assign pay items. 15. Generate the takeoff reports. Lesson: Reviewing Roadway Design Project Data 5

6 Guidelines Keep the following guidelines in mind when designing a roadway: Prior to starting a design, identify, gather, organize, and document the design parameters and criteria that apply to the project in order to make sure they are followed correctly. It is good practice to keep the names of alignments, layout profiles, subassemblies, assemblies, and corridor regions logical and simple but also descriptive to help in identification by others or yourself at a later time. Use data shortcuts to reference alignments and surfaces from single-source drawing files to keep project team members in synch. Design Parameters and Criteria The design standards, parameters, and criteria provided in this lesson simulate some of the standard guidelines a roadway designer follows. In the United States, most design parameters and criteria for roadway design are based on the minimum values of the AASHTO guidelines. STH 25 The project design parameters and criteria for STH 25 are: The design speed is 60 MPH before Sta and 45 MPH after Sta The design traffic volume is an Average Daily Traffic (ADT) of Use AASHTO 2001 Design Standards: emax 6% Minimum Radius Table, four-lane Transition Length Table, and Crowned Roadway Attainment Method (Sta to Sta ). Use AASHTO 2001 Design Standards: emax 6% Minimum Radius Table, two-lane Transition Length Table, and Crowned Roadway Attainment Method (Sta to Sta ). Use AASHTO 2001 Design Standards: Minimum K Tables for Stopping Sight Distance, Passing Sight Distance, and Headlight Sight Distance. The proposed horizontal alignment is to follow the existing road centerline and parallel the existing right-of-way where possible. STH 25 Sta is referenced to the intersection of STH 25 and Pine Drive. Station equation is needed at Sta Back = Sta Ahead. Profile grade is 5% maximum. Ditch grade is 0.5% minimum. Mill and overlay are to extend between the existing edges of the pavement of the traveled way. Variable depth milling (1 min.) and 4 overlay are to provide 2% slopes in normal crown sections and the required cross slopes in superelevated sections. The existing shoulder pavement and base course in the mill and overlay section are to be removed and replaced with new pavement and base course. The existing ditch bottom, in the mill and overlay cut section, is to follow the sub-base daylight point offset. The ditch backslope is to extend out to daylight existing ground. The four-lane divided median width is to be Chapter 1: Introduction to Roadway Design

7 Pine Drive The project design parameters and criteria for Pine Drive are: The design speed is 30 MPH west of STH 25 and 50 MPH east of STH 25. The design traffic volume is an ADT of 40 west of STH 25 and 300 east of STH 25. Use AASHTO 2001 Design Standards: emax 6% Minimum Radius Table, two-lane Transition Length Table, and Crowned Roadway Attainment Method. Use AASHTO 2001 Design Standards: Minimum K Tables for Stopping Sight Distance, Passing Sight Distance, and Headlight Sight Distance. Profile grade is to be 8% maximum. Intersection The project design parameters and criteria for the STH 25 and Pine Drive intersection are: Maintain a normal crown on STH 25 through the intersection. The angle of intersection (Q) = 75 degrees. Use a Type A intersection on reconstructed roadways when the through highway ADT exceeds 1000 and the side road ADT exceeds 100. Use a Type B intersection at all other side road intersections not meeting Type A intersection warrants. Intersections may be used in combination or separately for any one complete intersection, depending on design traffic volumes. Standard at-grade side road Type B intersection detail Lesson: Reviewing Roadway Design Project Data 7

8 Standard at-grade side road Type A intersection detail Typical Two-Lane Cross Sections The following typical cross-section criteria are used for the reconstructed roadway of the two-lane section of STH 25 and Pine Drive. See the Cross-Section Details table for roadway dimensions and cross slopes not shown. Reconstructed typical cross section for rural two-lane roadway 8 Chapter 1: Introduction to Roadway Design

9 Typical Four-Lane Cross Sections The following typical cross-section criteria are used for the new roadway construction of the four-lane divided and transition section of STH 25. The cross-section details for the four-lane divided roadway are the same as for the two-lane roadway, except as shown. See the Cross-Section Details table for roadway dimensions and cross slopes not shown. Reconstructed typical cross section for a rural, four-lane divided roadway Cross-Section Details The sub-base daylight point offset varies in the superelevation and superelevation transition areas. Lesson: Reviewing Roadway Design Project Data 9

10 Guardrail A guardrail is required in the mill and overlay segment when the fill height is greater than 10'. Partial typical cross section with a guardrail Roadway Transition The following roadway transition detail is used between the four-lane and two-lane sections of STH 25. Standard four-lane to two-lane transition detail 10 Chapter 1: Introduction to Roadway Design

11 Exercise: Examine Completed Roadway Design Project Data In this exercise, you examine the completed roadway design project data in a drawing file. To do this, you: Examine the external references, including: Basemap.dwg Right_of_Way.dwg Proposed.dwg Examine the existing data, including: Coordinate system Ground surface data reference Right-of-way alignments Road centerline points and 3-D feature lines from a survey Examine the proposed data, including: Alignments Profiles views Assemblies Intersection Corridors Corridor surfaces Examine External References 1. Open Examine Data.dwg. First, you examine the external references to this drawing. 2. On the ribbon: Click the Home tab> Layers panel > Layer State > External References. Click the View tab > Viewports panel > Named. 3. In the Viewports dialog box, select External References. Click OK. 4. On the View tab, click Palettes panel > External References Manager. 5. In the External References dialog box, note that: Basemap.dwg contains existing aerial survey topography. Right_of_Way.dwg contains existing rightof-way alignments that are displayed using a style that denotes existing right-of-way locations. Proposed.dwg contains proposed linework, such as the edge of pavement, edge of shoulder, curb and gutter radiuses, and guard rail and end terminals. Examine Existing Data The completed exercise Next, you examine the existing data beginning with the coordinate system drawing settings for this roadway design project. 1. In Toolspace, click the Settings tab. Right-click Examine_Data. Click Edit Drawing Settings. 2. In the Drawing Settings dialog box, click on the Units And Zone tab: Examine the coordinate system data. Note that if you know the code of the coordinate system you want, in this case BarronWI-F, you can enter it directly in the Selected Coordinate System Code area. A period (.) in this box means no zone has been selected. Click Cancel. Next, you examine the existing ground surface object. Lesson: Reviewing Roadway Design Project Data 11

12 3. On the: Default. 4. In the Viewports dialog box, select Existing Ground Surface Isometric. Click OK. 5. In Toolspace, on the Prospector tab. Expand Surfaces. Right-click Existing_Ground. Click Surface Properties. 6. In the Surface Properties dialog box, click the Information tab. Change Surface Style to Contours 1 and 5 (Design). Click OK. Note that the surface is a data reference from the location where you installed your dataset files:...\reference \Surface_Existing_Ground.dwg. 7. In the drawing area, select the Existing_Ground surface. Right-click. Click Surface Properties. 8. In the Surface Properties dialog box, on the Information tab, change Surface Style to Border Only. Click OK. Next, you examine the existing right-of-way miscellaneous alignment objects. 9. On the: Existing Right of Way. 10. In the Viewports dialog box, select Existing Right of Way. Click OK. 11. In Toolspace, on the Prospector tab: Expand Alignments, Miscellaneous Alignments. Right-click RW_STH_25_LT. Click Properties. 12. In the Alignment Properties dialog box, on the Information tab, change Object Style to Existing RW. Click OK. Notice the magenta alignment object that represents the left existing right-of-way line. This alignment is a data reference from the location where you installed your dataset files:...\reference\right_of_way.dwg. The alignment is masked through the intersections and is used for controlling subassembly daylight links in corridor target mapping. 13. In the drawing area, select the magenta line that represents the left existing right-of-way line alignment object (RW_STH_25_LT). Rightclick. Click Alignment Properties. 14. In the Alignment Properties dialog box, on the Information tab, change Object Style to _No_Display. Click OK. 15. On the: Existing Features and Points. 16. In the Viewports dialog box, select Existing Features and Points. Click OK. 17. In Toolspace, on the Prospector tab: Click Points. In the item view area, examine all of the road centerline points. These points were used as best-fit points to create the STH 25 centerline alignment. Expand Sites, Site Existing. Click Feature Lines. In the item view area, examine all of the road feature lines. The feature line Exist STH 25_ETW_LT represents the left edge of traveled way of STH 25. Exist STH 25_ETW_RT represents the right edge of traveled way, and Exist STH 25_Crown represents the crown line at the centerline. These feature lines are used for controlling the mill and overlay subassembly crown and trim offsets in the corridor target mapping. Examine the Proposed Data Next, you examine the proposed data beginning with the alignment objects. 1. On the: Alignments. 2. In the Viewports dialog box, select Alignments. Click OK. 3. In Toolspace, on the Prospector tab: Expand Alignments, Centerline Alignments, STH 25, Profiles. Note that the STH 25 and Pine Drive alignments, proposed profiles, and existing ground profiles are a data reference from...\reference\alignments.dwg. These alignments and their layout profiles are used as the baselines in the corridor. Expand Alignments, Offset Alignments, STH 25_NB, Profiles. 12 Chapter 1: Introduction to Roadway Design

13 Note that STH 25_SB, STH 25_NB, and STH 25_NB_TRANS alignments and their proposed profiles and existing ground profiles are a data reference from...\reference\alignments.dwg. The other offset alignments and their proposed profiles are created with the intersection design wizard and are located in this drawing file. Expand Alignments, Curb Return Alignment, STH 25_Pine Drive-NE-Quadrant, Profiles. Note that the curb return alignments and their layout profiles are created with the intersection design wizard and are located in this drawing file. Next, you examine the profile view objects. 4. On the: Default. 5. In the Viewports dialog box, select Profile Views. Click OK. 6. In Toolspace, on the Prospector tab: Expand Alignments, Centerline Alignments, STH 25, Profile Views. Note that the profile views are located in this drawing and that they contain data referenced surface and layout profiles from...\reference\alignments.dwg. Next, you examine the assemblies. 7. On the: Default. 8. In the Viewports dialog box, select Assemblies. Click OK. 9. In Toolspace, on the Prospector tab, expand Assemblies. Right-click STH 25. Click Zoom To. 10. In the drawing area, select the baseline object of the STH 25 assembly. Right-click. Click Assembly Properties. 11. In the Assembly Properties dialog box, on the Construction tab, examine the parameters of this typical two-lane assembly. Click Cancel. Next, you examine the intersection. 12. On the: Intersection. 13. In the Viewports dialog box, select Intersection. Click OK. 14. In Toolspace, on the Prospector tab: Expand Intersections. Notice that the intersection definition is out-of-date. This indicates that the intersection corridor regions are not synchronized with the intersection object. The corridor regions are out-of-date because they were manually edited after they were created using the Create Intersection wizard. Expand Intersections, STH 25_Pine Drive, Intersecting Alignments, STH 25. Note that these offset alignment objects are created using the Create Intersection wizard and are a part of the intersection object. Expand Intersections, STH 25_Pine Drive, Intersection Quadrants, NE - Quadrant. Note that these curb return alignment objects are created using the Create Intersection wizard and are a part of the intersection object. 15. In the drawing area, select the text object of the STH 25_Pine Drive intersection. Right-click. Click Edit Curb Return Parameters. 16. In the Intersection Curb Return Parameters dialog box, click Next to examine the properties of each quadrant. Close the dialog box. 17. Press ESC. Next, you examine the corridor. 18. On the: Default. 19. In the Viewports dialog box, select Corridor. Click OK. 20. In the drawing area, select the corridor. Rightclick. Click Corridor Properties. 21. In the Corridor Properties dialog box, on the Parameters tab: Examine the parameters of the corridor. For the Int_1 STH 25 baseline, click on the regions. Notice the region shapes highlighted in the viewport of the drawing file. Click Cancel. Next, you examine the corridor surface. Lesson: Reviewing Roadway Design Project Data 13

14 22. On the: Corridor Surface. 23. In the Viewports dialog box, select Corridor Surface. Click OK. 24. In Toolspace, on the Prospector tab, expand Surfaces. Right-click STH 25 Finish. Click Surface Properties. 25. In the Surface Properties dialog box: On the Information tab, change Surface Style to Contours 1 and 5 (Design). Click Apply. On Definition tab, look at bottom view pane. Note that the surface is created from corridor STH 25. Click Cancel. 26. Close the drawing. Do not save your changes. 14 Chapter 1: Introduction to Roadway Design

15 Chapter Summary In this chapter, you examined the roadway design workflow and the completed drawing files and reviewed the project scope, design parameters, and criteria for the roads being designed in this course. Having completed this chapter, you can: Examine the roadway design workflow and the completed drawing files and review the roadway project scope, design parameters, and criteria. Chapter Summary 15

16 16 Chapter 1: Introduction to Roadway Design