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Section 4: Preliminary Schematic

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Overview

Once data collection is substantially complete, the preliminary schematic activity phase begins. This section describes developing engineering solutions to satisfy the project need. Geometric alignments and typical sections are the major engineering variables set forth. An operational analysis is performed on alternatives to determine the Level of Service (LOS) of each.

Parameters needed for final design may proceed as long as the activities don’t affect objective consideration of alternatives in the NEPA review process or cause adverse environmental impacts.

Schematics are valuable to communicate design concepts to the parties involved in project development. A geometric schematic is required for new location, added capacity project, interstate ramp relocation, control of access, or an environmental impact statement. A list of schematic requirements can be found in the TxDOT Roadway Design Manual.

Districts establish Green Ribbon Master Plans for urban corridors with populations greater than 100,000. Conceptual guidance for landscape and aesthetic enhancements are considered, as well as bicycle and pedestrian accommodation.

Preliminary geotechnical surveys are conducted, if important to the decision making process. Preliminary pavement designs are developed so that project cost estimates can be updated.

For projects requiring environmental impact statement (EIS), control of access, new location, or added capacity requires Design Division approval of the geometric schematic. If the schematic requires an Interstate Access Justification Request (IAJR), FHWA will review and approve the schematic and IAJR. All schematic approvals are considered as “pending” until NEPA is clear.

This section includes the following subsections and tasks, many of which may be performed concurrently:

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Alternative Selection

20400. Evaluate corridor alternatives

20410. Perform preliminary Level of Service analysis

20420. Evaluate route alternatives

20430. Initiate railroad coordination

20440. Identify requirements for crossing navigable waters

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Geometrics

20450. Evaluate geometric alternatives

20460. Develop typical sections

20470. Prepare Landscape and Aesthetics Assessment

20480. Develop bicycle and pedestrian accommodation

20490. Update cost estimates

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Update cost estimates

20490. Update cost estimates

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20400: Evaluate corridor alternatives

Description. A transportation corridor is essentially a linear broad band that follows a general travel flow. Influenced by logical, existing, and forecast travel patterns, it includes interconnected networks of adjacent travel modes all affected by transportation and mobility needs. Preparing corridor alternatives during preliminary design involves developing many conceptual alternatives that are feasible and reasonable in terms of construction, operation, and satisfying project goals. Corridors may be managed and serve a transportation network that carries freight, transit, cars, and alternate transportation modes by bicyclist and pedestrian. The corridor may be urban or may be a longer intercity corridor serving a variety of trip purposes. The corridor alternatives evaluation end product is a single, preferred corridor and conceptual typical sections. This preferred corridor will be carried forward to the next stage, 20420: Evaluate route alternatives.

Conceptual typical sections define basic elements including number and type of lanes (e.g., single versus high occupancy vehicle lanes), shoulders, type and range of median width, possible frontage roads, and range of offset to right of way limits. Details such as cross slopes, side slopes, pavement structure, and station limits are typically not needed to define a particular concept. The number of lanes should be based on the design year capacity needed to operate at a desired Level of Service (LOS).

Although a more formal evaluation process will follow for selecting the preferred alternative, interim screening levels may be necessary to reduce the list of alternatives to a manageable number. Screening criteria should be based on characteristic elements that differentiate alternatives.

Pertinent Project Types. New location, added capacity, or controlled access projects or projects requiring an environmental impact statement.

Responsible Party. Project manager

Subtasks.

Helpful Suggestions.

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  • Obtain traffic data early. It may take three to four months to obtain design traffic data.
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  • Early on, determine the availability and preference for base mapping such as aerial photos, USGS maps, topographic maps, or TxDOT county maps.
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  • Public involvement is a major factor in determining corridor alternatives. Plan public meeting(s) to obtain input.
    • Anchor: #YCNDMXLP
  • Establish a clear labeling or naming convention for alternatives.
    • Anchor: #FWTHKALO
  • Anticipate the need for creating options to an alternative or possible combinations of alternatives.
    • Anchor: #NUCRIDFV
  • Some evaluation criteria may be less relevant than others in the decision making process; therefore, it is important that each element is weighted if a matrix/numerical analysis is performed.
    • Anchor: #BXMRACOD
  • Doing a planning safety analysis makes safety an integrated component of the design.
    • Anchor: #AKUOQDAA
  • Keep alternatives basic in definition and avoid dwelling on details that are not significant at a conceptual level.
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  • Prepare study area map to evaluate environmental challenges.
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  • Review topography and floodplain maps to estimate whether adverse hydraulic impacts can occur.

Critical Sequencing.

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  • Request traffic data (e.g., traffic volumes) for use in defining typical sections early.
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  • Through site visits or reviewing existing data, develop a clear understanding of the study area limits as well as corridor network function before developing alternatives.

Resource Material.

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20410: Perform preliminary Level of Service analysis

Description. A planning Level of Service (LOS) analysis uses preliminary traffic volume data for the design year. Analyze the existing facility and current volumes for a baseline to compare alternate designs. After project alternatives are fully defined, including the “no-build” alternative, a planning LOS analysis can be conducted. Given a desired LOS for the design year, the typical number of lanes proposed is usually based on projected design year traffic volumes. The results combined with cost estimates may also determine cost effectiveness.

Pertinent Project Types. New construction, multilane highway reconstruction, and interstate projects.

Responsible Party. Roadway design engineer or traffic engineer

Subtasks.

Resource Material.

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20420: Evaluate route alternatives

Description. A route alternative comparison is performed within the preferred corridor to identify the most feasible and reasonable route alternatives. The evaluation process developed for selecting alternatives is typically based on criteria addressing project objectives, commitments, environmental impact, and stakeholder input. Quality, organization, documentation, and presentation of data are critical to the success and credibility of the evaluation and selection process. Thorough analyses of alternatives supports a well-defined scope, minimizes scope creep, and incremental cost effects later.

Doing a planning safety analysis makes safety an integrated component of the final design. AASHTO Highway Safety Manual (HSM) and software can provide a quantitative safety analysis of the route to identify alternate forms of intersecting traffic control and capacity improvement.

If funding authorization involves federal funds and the preliminary estimates indicate the total project cost may approach the threshold for a Value Engineering Study, contact the Design Division Value Engineering representative to discuss options. See Task 20600: Conduct Value Engineering (VE) study.

Pertinent Project Types. New location, added capacity, or controlled access projects or projects requiring an environmental impact statement.

Responsible Party. Project manager

Subtasks.

Helpful Suggestions.

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  • Obtain traffic data. It may take three to four months to obtain design traffic data.
    • Anchor: #UDQFGOHK
  • Early on, determine the availability and preference for base mapping such as aerial photos, USGS maps, topographic maps, floodplain maps, or TxDOT county maps.
    • Anchor: #PPJDXJFY
  • Public input is required. Ensure comments and concerns are addressed in route analyses. Public patronage encourages community support and goodwill.
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  • In describing alternatives, use intersecting roads or landmarks instead of stationing.
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  • Establish a clear labeling or naming convention for alternatives.
    • Anchor: #MGMBREJG
  • Anticipate the need for creating options to an alternative and possible combinations of alternatives.
    • Anchor: #PIAWGEMK
  • Some evaluation criteria may be less relevant than others in the decision making process. Therefore, it is important that each element is weighted if a matrix/numerical analysis is performed.
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  • Keep alternatives basic in definition and avoid dwelling on details that are not significant at a concept level.

Critical Sequencing. The most feasible and reasonable route alternatives must be selected before evaluating geometric alternatives.

Resource Material.

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20430: Initiate railroad coordination

Description. All work within railroad right of way (ROW) must be coordinated with the railroad owners. TxDOT may not perform work within railroad ROW without the proper agreement, liability insurance, and special provisions.

Approval for new, at grade railroad crossings is difficult to obtain. Generally, an existing at grade crossing in the general project area must be closed or grade separated so no net increase in at grade crossings results. TxDOT usually bears the burden of finding these “trade off” crossings and negotiating with third parties, if crossings are located off the State highway system.

Early coordination reduces construction time extension claims and project delivery delays, which increase project cost. Depending on the impact to the railroad, the negotiations, plans, and final agreement can take about four to 24 months. Federal Aid Highway Program projects are subject to compliance audit for railroad agreements completed prior to the project construction authorization date.

Pertinent Project Types. Projects involving rail-highway crossings, either at grade or grade separated, and all projects involving joint usage with the railroad (e.g., shared ditches).

Responsible Party. Project manager or roadway design engineer

Subtasks.

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  • District railroad coordinator should begin work early with Traffic Operations Division - Rail Safety Section (TRF-RSS), the office of primary negotiation with the rail companies.
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  • Locate all potential railroad crossings within project limits.
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  • Determine existing crossing conditions and traffic control. Investigate the need for interconnection between various signals.
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  • Identify opportunities to close or consolidate at grade crossings.
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  • Obtain a train crossing schedule from railroad owners. Inquire into major railroad line improvement plans. Obtain approval of clearances for grade separated structures.
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  • Develop recommendations for proposed rail highway crossings.
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  • Document all correspondence regarding the design of the railroad features.
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  • Task 50480: Develop Exhibit A for railroad agreements. The Traffic Operations Division - Rail Safety Section prepares and negotiates construction and maintenance agreements with railroad company.
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  • Provide railroad agreement completion date on Form 1002, page 2.

Helpful Suggestions.

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  • Consider installing new, and upgrading existing, railroad warning devices at railroad crossings within and near the project limits. Coordinate this with the railroad owner through TRF-RSS. Railroad owners are responsible for maintaining railroad active warning devices and signs.
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  • Consider interconnecting closely spaced, active railroad warning devices and highway traffic signals.
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  • Consider replacing the crossing surface and subgrade. District rail coordinators should inspect the crossing surfaces to evaluate if crossing is a candidate for the Replanking Program.

Critical Sequencing.

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  • Initial railroad coordination should be conducted before selecting a preferred alternative because railroad issues may affect final alternative selection.

Authority.

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20440: Identify requirements for crossing navigable waters

Description. The requirements for crossing navigable waters must be determined to ensure that projects are in compliance with federal regulations. All projects affecting a navigable waterway require coordination with the U.S. Coast Guard (USCG) and the U.S. Army Corps of Engineers (USACE).

Pertinent Project Types. Projects affecting a navigable waterway

Subtasks.

Responsible Party. District environmental coordinator

Helpful Suggestions.

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  • For a proposed bridge crossing navigable waterways, lights and/or signals will be required, which warn of bridge piers, caps, and beams
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  • Assistance related to bridge requirements is available from the Bridge Division Project Development Section.

Critical Sequencing.

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  • When design criteria must be met to secure a permit, coordinate this early in schematic development.

Authority.

Resource Material.

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20450: Evaluate geometric alternatives

Description. Controlling design criteria are shown on preliminary schematics. This requires developing alignments for mainlanes, ramps, crossroads, and interchanges to ensure that design controls are satisfied. The end product is a preferred alternative selection.

Design the alignments to fit constraints that were identified earlier. The preliminary hydraulic design should be reviewed so the vertical “profile” alignment will accommodate drainage structures. See Task 20560: Perform preliminary hydraulic analysis/design.

At this stage, geometric alignments should be defined enough to determine basic requirements such as required drainage structures, right of way (ROW), business or home relocations, and major utility conflicts. This information can be used in comparing alternatives, along with safety, environmental, travel efficiency and other considerations. Later, a preferred geometric alignment will be selected, and a more detailed schematic may be prepared on survey controlled base mapping.

The preferred alignment and associated geometrics, including typical section(s), will be formally labeled as “preferred” and presented to the public. Reasons for establishing an alignment as preferred must be clear and should be recorded in project files for future reference.

A list of items to show on a schematic is available in the TxDOT Roadway Design Manual .

A preliminary schematic will accomplish the following goals:

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  • Formulate design concepts for the project.
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  • Show interrelating design elements such as typical sections, bridge and drainage structures, traffic and turning data, project constraints, etc.
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  • Serve as a basis for approval, agreement on scope, design, etc., between districts, divisions, FHWA, counties, cities, and railroads, as applicable.
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  • Establish relationships between the project and environment.
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  • Define ROW and access control requirements.
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  • Act as a public information communication tool. For better public understanding of a project, a schematic may be supplemented by a physical scale model, three-dimension graphics demonstration, or computer animation. These may be needed for costly, controversial or complex projects.
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  • Serve as the guide for detailed design and plan preparation.

Pertinent Project Types. New location, added capacity, controlled access projects, or projects requiring an environmental impact statement.

Responsible Party. Roadway design engineer

Subtasks.

Helpful Suggestions.

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  • Display schematic for public view. Make the schematic as uncluttered as possible.
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  • Use enlarged drawings to show areas of a project having large amounts of detail.

Resource Material. The following table indicates where more information related to the evaluation of geometric alternatives may be found:

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Topic

Reference

Roadway design criteria

TxDOT Roadway Design Manual

Schematic checklist

TxDOT Roadway Design Manual, Chapter 1

Bridge planning

TxDOT Bridge Project Development Manual

Bridge design

TxDOT Bridge Design Manual - LRFD

Landscape and aesthetics

TxDOT Landscape and Aesthetics Design Manual, Chapter 3

Hydraulics

TxDOT Hydraulic Design Manual

Bike lane/bike trail design criteria

AASHTO Guide for the Development of Bicycle Facilities

Pedestrian Accommodation

U.S. Access Board – PROWAG

AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities

Quantitative safety evaluation

AASHTO Highway Safety Manual and software


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20460: Develop typical sections

Description. Typical sections are developed as part of selecting design alternatives. The typical section geometry should include the following information:

Design criteria for features shown on typical sections can be found in TxDOT's Roadway Design Manual, Chapter 2. If pavement design information is available at this time, it may be shown on the typical section. See Task 20510: Prepare pavement design report.

Authority.

Pertinent Project Types. All projects

Responsible Party. Roadway design engineer

Resource Material.

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20470: Prepare Landscape and Aesthetics Assessment

Description. The landscape and aesthetics assessment (LAA) identifies the issues that will affect the physical design form and detail of the project. A landscape architect should be consulted to prepare an LAA. See the Landscape and Aesthetics Design Manual, Chapter 3, Section 2, Landscape and Aesthetics Assessment.

Issues and procedures involve field observation and participation in or review of public participation venues. The goal is to maximize design flexibility. Verify if the project is in a Green Ribbon Master Plan that includes city populations greater than 100,000. A Green Ribbon Master Plan provides conceptual guidance to planning and design.

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  • Project scope
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  • Corridor inventory such as, physical properties of the project site, grades, horizontal curves and sight distance obstructions, median widths, right of way widths available, and neighborhood context
    • Anchor: #QTKPKCBP
  • Public issues from public participation process
    • Anchor: #MLUIJCSR
  • Identify assets and liabilities
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  • Sensitivity of the corridor such as established schools, neighborhoods, shopping centers, medical facilities, historical areas
    • Anchor: #BJONHHXE
  • Identify issues relating to visual perception of the transportation corridor such as materials, colors, appropriate design themes
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  • Cost sharing opportunities
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  • Gather information which assists in estimating development costs

The district or Design Division landscape architect can assist in providing guidance upon request.

Pertinent Project Types. New construction and reconstruction projects

Responsible Party. Roadway design engineer

Subtasks.

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  • If the project area is in a Green Ribbon Master Plan, observe plan policy.
    • Anchor: #MELXWHYY
  • Coordinate landscape/aesthetics plan with district or Design Division landscape architect.
    • Anchor: #UVYXRSTE
  • Obtain data on existing conditions from soil surveys and topographic surveys.
    • Anchor: #VWSGOUXE
  • Prepare concept proposal including data such as construction and maintenance costs.
    • Anchor: #SKBXMUIG
  • Consider environmental justice issues, if unusual or high-cost amenities are proposed that vary from usual TxDOT practice.

Authority.

Resource Material.

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20480: Develop bicycle and pedestrian accommodation

Description. Accommodations for bicycle and pedestrian travel should be given full consideration on all highway projects and during construction, specifically on Federal-aid projects. Where these non-motorized transportation modes are reasonable to expect, preliminary plans should be developed to include safe bicycle and pedestrian transportation accommodation.

Public rights of way and facilities are required to be accessible for all pedestrians.

Pertinent Project Types. All projects

Responsible Party. Roadway design engineer

Subtasks.

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  • Decide what accommodation type can be reasonably provided.
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  • Provide a reasonable alternative route, if an existing bicycle and pedestrian facility is being affected by proposed construction.
    • Anchor: #NEWWCULO
  • If a bridge deck is being rehabilitated or replaced on a highway, which permits bicycles and pedestrians to operate at each end of the bridge, provide safe accommodation on the replaced or rehabilitated bridge.
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  • Coordinate with public transportation providers to facilitate provision of intermodal connections.

Helpful Suggestions.

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  • Refer to local bicycle and pedestrian plans, if applicable.
    • Anchor: #ALJAWIWJ
  • Coordinate with the State Bicycle and Pedestrian Coordinator during the planning stage.
    • Anchor: #FDQJWHIF
  • Where new bicycle and pedestrian facilities are proposed, include sufficient information to explain the reasons for facility selection in the environmental effects statement.

Critical Sequencing.

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  • Include provisions for bicycle and pedestrian accommodations in the preliminary schematic.

Authority

Resource Material.

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20490: Update cost estimates

Description. Construction and right of way cost estimates, and corresponding DCIS and PeopleSoft data, should be updated periodically to reflect project changes. Any cost overruns will affect district programming of projects and should be identified as early as possible. For more information, see Task 10200: Prepare cost estimate. The cost estimates should accurately identify approved funding sources (federal, state, and local participation.) Eligible utility adjustment costs must be included in the right of way cost estimate.

If updated estimate total cost meets or approaches the value engineering (VE) threshold, consider conducting a VE Study. See Value Engineering of this chapter.

Pertinent Project Types. All projects

Responsible Party. Roadway design engineer

Helpful Suggestions.

When recalculating the cost estimate, be sure to use current unit bid prices. Consider factors such as the following:

Resources.
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