4.4 Geometric Schematic Design
Once all alignment alternatives have been fully analyzed, a recommended alternative is selected. Additional design tasks are performed to prepare the geometric schematic. The geometric schematic is submitted to the District for review through multiple milestone submittals (e.g., 30%/60%/90% or Preliminary/Final) and is submitted for final review and approval by the District and possibly FHWA (if warranted). See
for further guidance on submission, review and approval of the geometric schematic.
The completed geometric schematic may serve as the Initial (30%) milestone submittal for project development (refer to TxDOT’s
PS&E Preparation Manual
for milestone submittals) and should accomplish the following goals:- Formulate final design concepts for the project;
- Show interrelating design elements such as typical sections, intersection control; bridge and drainage structures, traffic and turning data, project constraints, etc.;
- Serve as the basis for development of the Preliminary Bridge Layout Review (PBLR) submittal (refer to TxDOT’s PS&E Preparation Manual and theBridge Project Development Manualfor more details)
- Serve as a basis for approval, agreement on scope, design, etc., between Districts, Divisions, FHWA, counties, cities, and railroads, as applicable;
- Establish relationships between the project and the environment;
- Define ROW and access control requirements;
- Act as a public information communication tool. For better public understanding of a project, a schematic may be supplemented by a three-dimensional graphics demonstration, computer animation or a physical scale model. These may be needed for costly, controversial, or complex projects; and
- Serve as the guide for the detailed design and plan preparation.
See the Schematic QC Checklist for guidance on developing the Geometric Schematic for review and approval.
The following subsections describe the preliminary engineering design tasks that are typically performed to develop the Geometric Schematic.
4.4.1 Roadway
4.4.1.1 Typical Section Optimization
Typical sections are optimized to reflect any changes to the recommended alternative and incorporate results of the Safer by Design tool (see
).
Once the recommended alternative is selected, typical sections are optimized to ensure that all design criteria is met and all desired elements are incorporated into the typical section including multimodal accommodations, clear zone, border width, utility strip, etc. Typical sections must meet the design criteria specified in the RDM and
must be developed for all roadway components
including mainlanes, frontage roads, ramps, turnarounds and cross streets.Evaluate the typical sections in accordance with the RDM’s Performance Based Practical Design methodology.
4.4.1.2 Horizontal and Vertical Alignment Refinement
Horizontal and vertical alignments are fully designed once a recommended alternative is selected. Horizontal/vertical alignments are designed for
all roadway components
including mainlanes, frontage roads, ramps, turnarounds and cross streets. All alignments must meet the design criteria specified in the RDM.Considerations in horizontal/vertical alignment design include:
- Ensure vertical clearances are met for bridge structures including bridges over turnarounds – determine if route is on the Texas Highway Freight Network (THFN (Statewide Planning Map);
- Determine if the route is part of a hurricane evacuation route (Statewide Planning Map);
- Avoid changes to ROW limits and locations of ramps shown on the schematic after DES approval review or FHWA Federal action interstate access approval; and
- Consider underground features, such as utilities, storm sewer systems and septic tank systems, when making alignment adjustments.
Changes to the horizontal and vertical alignments after a public meeting or hearing may require TxDOT to repeat the review and approval process for the environmental document and hold additional meetings/hearings. Minor adjustments to alignments may be made by the designer if the change is feasible and does not compromise project design criteria.
Substantial changes to an approved geometric schematic will require submission of the revised schematic to DES.
Coordinate any changes to the design with the District Environmental Coordinator to ensure that environmental studies and documents are appropriately updated. Some changes may warrant revisions to previously completed environmental studies. See
for more information regarding the coordination of design and environmental tasks.
4.4.1.3 Safer by Design Tools
TxDOT developed the Safer by Design tools (formerly the Safety Scoring Tools) that are used to assist designers in evaluating potential safety enhancements during project development and design.
The Safer by Design Tools incorporate quantified effects of changes in design parameters such as lane and shoulder width, horizontal and vertical curve geometry, rumble strips and clearances to objects, thereby allowing designers to examine the effects and tradeoffs involved in design decisions.
The Safer by Design tools should be used prior to obtaining any additional survey and/or SUE to ensure that ROW that may be needed for the optimized design is identified. Districts are required to document the initial and final safety score, for applicable projects, on the Form 1002, which are required with interim and final PS&E submissions.
The tool is not designed or intended to make decisions for the designer, but rather to provide an objective, data-driven aid that allows the designer to assess and evaluate how changes in design parameters can affect safety.
4.4.1.4 Bicycle and Pedestrian Accommodation Development
Per the USDOT Bicycle and Pedestrian Planning, Program, and Project Development Guidance memo: “Providing safe, accessible, comfortable, equitable, and interconnected networks for bicycling and walking creates an integrated, intermodal transportation system that provides travelers with a real choice of transportation modes. Bicyclists, pedestrians, and micromobility users have the same origins and destinations as other transportation system users. It is important for all users to have safe, accessible, equitable, and convenient access to destinations such as airports, ports, ferry services, transit stations and stops, and other intermodal facilities as well as access to jobs, education, health care, and other essential services. Transportation professionals are encouraged to plan, design, construct, and maintain transportation facilities to support complete networks, especially on urban and suburban nonfreeway arterials with posted speed limits less than 50 miles per hour (mph), or to rural arterials that serve as main streets in smaller communities”.
Where these active, non-motorized transportation modes are expected, preliminary plans must be developed to include safe bicycle and pedestrian transportation accommodation. Bicycle and pedestrian design criteria and considerations can be found in the RDM.
Considerations in the design of bicycle and pedestrian accommodations include:
- Determine if the project location is part of the TxDOT Bicycle Tourism Trials Example Network to determine design requirements for this type of facility;
- Consult local, regional and District bicycle and pedestrian plans if available (refer to the Active Transportation Plan Inventory webpage);
- Provide safe accommodations on replaced or rehabilitated bridges by providing accommodation of pedestrians or bicyclist if provided at a reasonable cost;
- Refer to TAMES/TCAP Toolbox to identify existing ADA barrier information;
- Coordinate with public transportation providers to facilitate provision of intermodal connections; and
- Where new bicycle and pedestrian facilities are proposed, include sufficient information to explain the reasons for facility selection in the environmental effects statement.
4.4.2 Additional Survey and Subsurface Utility Engineering Needs
Additional survey and subsurface utility engineering (SUE) investigations may be needed to obtain more specific field data once the recommended alternative is selected and the design elements have been optimized.
4.4.2.1 Survey
Additional survey may be needed to tie-in project-specific details including:
- Blank spots from previous LiDAR surveys;
- Existing above ground utilities;
- Existing bridge details;
- Existing drainage structure details (culverts, manholes, etc.);
- Existing driveway details;
- Existing ROW limits;
- Existing signals/pushbuttons, curb ramps, and sidewalk;
- Hydrographic survey for drainage design;
- Location of proposed geotechnical boreholes; and
- Location of wetlands.
4.4.2.2 SUE
Additional subsurface utility investigations may be needed to determine location and depth of existing underground utilities. The level of SUE investigation needed depends on the potential for utility conflicts. See
for more discussion on SUE.
4.4.3 Drainage Design
The preliminary drainage design is performed to a sufficient level of detail to determine the placement, size and performance of proposed drainage structures on a project. The proposed drainage structures are placed on the geometric schematic.
The design of these structures should provide sufficient information to determine ROW needs and/or temporary or permanent drainage easements.
4.4.3.1 Hydrology Design
A hydrologic study is performed to estimate flood magnitudes (i.e., Annual Exceedance Probability (AEP)) caused by precipitation. An analysis provides the designer with fundamental data necessary to perform preliminary sizing of drainage facilities and bridges. Data compiled includes peak runoff (discharge) and discharge hydrographs. Refer to TxDOT’s
Hydraulic Design Manual
to determine what projects require a hydrologic study to be performed and methods to use.Any previous hydrologic studies, reports, as-built construction plans, bridge inspection reports and available stream gage data should be obtained and reviewed prior to beginning the hydrologic design.
Other valuable reports to obtain include soil surveys, U.S. Natural Resources Conservation Service (NRCS) reports, as well as USGS and FEMA flood maps.
Coordinate with LGs for any type of zoning and land use maps, or specific local requirements to incorporate when performing the hydrologic design.
4.4.3.2 Hydraulic Design
The purpose of the hydraulic design is to determine the approximate elevations and sizes of cross drainage structures and to establish their effects on the roadway profile. The analysis conducted must result in an estimate of the most efficient, cost-effective drainage facilities that can accommodate the design storm.
A hydraulic analysis is required to create the roadway's preliminary profiles for all projects affecting existing drainage, including those that add a concrete median barrier to an existing facility.
The type of drainage facilities provided in the hydraulic design will be determined by the highway classification, ROW, geometry and other considerations. The primary focus at this stage is to balance traffic safety and hydraulic efficiency and to comply with any regulations such as FEMA.
Other major considerations must be determined, such as the need for large storm drain structures, detention ponds, pump stations, and other hydraulic facilities; these must be assessed for cost and ROW requirements. Refer to TxDOT’s
Hydraulic Design Manual
for specific details in performing the hydraulic design.A preliminary drainage report is developed and submitted for review by the District and DES - H&H Section. The preliminary drainage report details all of the hydrologic and hydraulic analysis and design including the scour analysis for bridge structures over streams.
4.4.4 Traffic Control Planning
Preliminary traffic control planning is needed during the development of the geometric schematic to ensure that the ultimate design is constructable. Planning for traffic control in this phase of schematic development allows for the anticipation and mitigation of potential traffic disruptions during construction.
Early planning will reduce overall project costs by avoiding delays and redesign later on during the project due to requirements that are not considered soon enough (e.g., buffer zones, edge drop-offs, temporary pavement, temporary pedestrian access route (TPAR) barrier locations, extension of drainage structures, detention areas and offsets to travel lanes). Early traffic control planning also incorporates stakeholder input for preferred alternative routes, detours and construction scheduling.
Refer to the RDM for temporary traffic control criteria
. Consult the TMUTCD and the Traffic Standards to develop the preliminary traffic control plan.4.4.5 Structures
4.4.5.1 Bridges
The location of proposed bridges must be determined early in project development. Characteristics such as limits of bridge, bent locations, and span type and lengths of bridges crossing water can usually be set with strong certainty early in project development. Planning for overpasses, underpasses and interchanges requires an iterative process to satisfy structural capability and horizontal and vertical clearance requirements between roadways and bridges.
Culverts with a total span greater than or equal to 20 feet are considered bridge-class culverts and their design must follow span bridge guidelines.
Bridge layouts can be created once horizontal/vertical alignments, typical sections and drainage design are developed. The bridge layouts are sent to the District and BRG for review. This submission is referred to as the Preliminary Bridge Layout Review (PBLR) and it typically occurs between the Initial (30%) and Detailed (60%) plans milestones (refer to the
PS&E Preparation Manual
and the Bridge Project Development Manual
for more details). Accommodations for future bridge widening should be considered during the preliminary planning. Preliminary bridge layout reviews include bridge class culverts.If the project is on or near railroad ROW, the RRD will coordinate with the specific railroad. Refer to the TxDOT.gov Railroad Design Guidelines webpage for details on design, coordination and agreements required for specific railroads.
Considerations in the preliminary planning for bridges include:
- Identify applicable Federal Emergency Management Agency (FEMA), U.S. Corps of Engineers (COE) and U.S. Coast Guard (USCG) constraints, studies required, and coordination and permits required;
- Review railroad requirements and coordinate with RRD for railroad crossings;
- Identify and determine historic age considerations and constraints;
- Identify hazardous materials issues and abatement requirements;
- Identify type, size, and location of existing and proposed bridges and document in the DSR;
- Determine vertical and horizontal clearance requirements;
- Identify utilities that will need to be removed from the existing bridge prior to construction;
- Identify potential conflicts with foundations, including existing foundations or subsurface utilities – obtain as-built plans from all structures previously constructed to determine locations of buried foundations;
- Determine load rating for bridge widening and obtain condition survey;
- Consider rehabilitation and widening of the existing structure versus replacement;
- Review proposed bridge cross sections with local public agency or railroad company when grade separation structures involve facilities not owned or maintained by TxDOT; and
- Coordinate with District TP&D to determine if Advanced Funding Agreement is in place, if applicable.
Coordinate with the District Bridge Engineer to determine District specific PBLR submission requirements. Detailed bridge design should not begin prior to approval of the PBLR.
4.4.5.2 Retaining/Sound Walls
Preliminary retaining wall locations are established as part of developing the geometric schematic. Preliminary sound wall locations are established based on the traffic noise analysis. Retaining wall or sound wall locations may be revised as the project development progresses.
4.4.5.2.1 Sound Walls
A sound wall is a structure designed and constructed to reduce the impact of traffic-related noise on nearby communities and sensitive areas. A noise study analysis must be performed to determine where noise impacts are predicted and will determine recommendations for placement of sound walls.
Considerations in the placement of sound walls include:
- Refer to the traffic noise analysis for the location and dimensions of the proposed sound wall;
- Determine if aesthetics are to be included as this will affect the design. For sound walls adjacent to residential areas and parklands, aesthetics may play an important role in developing the wall. Coordinate with planners, landscape architects and community groups early in project development;
- The placement of the sound wall often depends on existing or proposed utility lines. Coordinate early with utility owners to determine locations of existing and proposed lines;
- Determine if a berm may be effectively used to mitigate noise. It may be used with a sound wall barrier and allow for a shorter, more aesthetically pleasing wall;
- Evaluate the need for future access to adjacent property and potential openings in the wall; and
- Determine if placement of the sound wall can be made within the existing ROW (consider the design and construction of the wall footing) or if additional ROW or permanent easements are needed.
Locating retaining walls and/or sound walls will assist in determining locations of needed soil core borings for foundation design.
4.4.5.2.2 Retaining Walls
A retaining wall is a structure designed and constructed to resist the lateral pressure of soil. TxDOT divides retaining walls into permanent and temporary walls. A permanent retaining wall is designed to have a service life of 75 years, while a temporary wall has a service life of 3 years.
Considerations in the placement of retaining walls include:
- Compare retaining wall cost to bridge cost to determine height at which bridge is more cost effective (typically at 20-ft height, bridge structure becomes more feasible);
- Determine if the retaining wall also needs to act as a sound wall;
- Determine if the retaining wall will be supporting traffic lanes. If so, the design must account for traffic loading and barrier affect loading;
- Check sight distance for walls in cut sections at intersecting streets and driveways;
- Determine if street lights, overhead bridge signs, concrete traffic barriers, or traffic signs will be attached to the wall;
- Consider width of retaining wall base during construction and placement near ROW line (buried portions of permanent structures cannot be placed outside of the ROW line);
- Ensure adequate clear zone between travel lanes and the retaining wall is provided; and
- Do not place the retaining wall in a gore area.
4.4.6 Geotechnical Surveys
Preliminary geotechnical surveys can vary from simple, visual inspections to various forms of subsurface exploration, depending on information needed. Once preliminary bridge, retaining wall and sound wall locations are determined, preliminary geotechnical surveys can be performed. Preliminary geotechnical surveys are performed to guide early project layout and design and determine feasibility of the preliminary design and limitations on construction staging. Preliminary geotechnical survey can help determine if certain design options are viable. (i.e., below grade/tunnel options). Preliminary geotechnical testing also serves to determine if additional, more in-depth geotechnical testing is needed.
For large structures, preliminary geotechnical surveys form the basis for more rigorous testing. On major projects, a small number of preliminary borings must be obtained to aid in the preliminary project layout.
Geotechnical surveys for pavement design may also be needed and may include roadway pavement testing such as Falling Weight Deflectometer (FWD) testing.
Considerations for performing preliminary geotechnical surveys include:
- Consult existing as-built construction plans and District laboratory staff to obtain existing test information if available – this can assist in determining the extent of additional testing that might be needed;
- Obtain ROE prior to entering private property for geotechnical testing;
- Locate utilities prior to testing – geotechnical firms will typically do this prior to testing, however, additional coordination with the geotechnical firm and utility companies to ensure this happens should be performed; and
- Coordinate with District environmental staff for any type of hazardous soil materials in the testing areas.
4.4.6.1 Preliminary Pavement Design and Report
A preliminary pavement design is performed early in project development to ensure a viable design is generated. The pavement structure represents one of the costliest items in a typical highway project budget. The objective for completing a preliminary pavement design early is to select a pavement structure capable of carrying traffic loads safely, comfortably and with minimum physical deterioration and to ensure the project is adequately funded for the desired pavement section. Waiting to develop the pavement design often results in reduction of the pavement structure due to restricted project funding.
The cost of different pavement options should be evaluated prior to pavement section selection.
A pavement design and pavement design report are required for the following project types that are over 500 ft. long:
- New location (flexible and rigid);
- Reconstruction (flexible and rigid);
- Rehabilitation (3R) (flexible and rigid); and
- Unbonded concrete overlays of existing rigid pavements.
Each District maintains and updates a pavement design standard operating procedure (SOP). The SOP will also establish the final authority for pavement design within the District.
4.4.7 Utilities
Known utility facilities within the ROW (existing and proposed) are shown on the geometric schematic. The designer should obtain information on existing utilities from utility owners and include the location of existing utilities on the geometric schematic.
A utility layout may be prepared more easily by performing the following steps:
- Send the schematic to utility owners who do not have utility plans readily available;
- Ask utility owners to draw their utilities on the schematic with distances referenced to the ROW or other reference points; and
- Use additional SUE to identify underground utilities.
Refer to TxDOT’s ROW
Utilities Manual
for details on the TxDOT-Utility Cooperative Management Process.4.4.7.1 Potential Utility Conflicts Identification
Utility conflicts refer to physical conflicts between existing utilities and the proposed transportation facility construction. Utility conflicts also refer to utilities not complying with TxDOT's Utility Accommodation Rules (UAR), such as utilities not complying with location, cover, or clearance requirements. After developing a utility layout, the designer can determine potential utility conflicts. If geospatial data is available, a 3D model review can be performed. Knowledge of these conflicts assists the utility owners in budgeting for anticipated adjustment costs.
Early utility coordination cuts construction time extension claims and delays that increase project costs.
Considerations to avoid utility conflicts:
- Revise alignments and project features to avoid utilities when possible before requesting that the utilities be moved. Utility adjustment can be expensive and time-consuming so it must be done only when it is unavoidable; and
- Advise utility owners of potential conflicts as soon as possible.One to two yearsmay be needed to budget, design, and complete required adjustments.
For more detailed information on the utility accommodation process, see
.
It is It is important to notify utility owners of potential noise mitigation locations proposed for a project to avoid relocating utilities that could provide conflict for the proposed sound wall.
4.4.8 Traffic Design
4.4.8.1 Large Guide Signs
Large guide signs direct road users along streets and highways and are shown on the geometric schematic. Large guide signs show route designations, destinations, directions, distances, services, points of interest, and other geographical, recreational or cultural information.
Freeways and expressways use large guide signs that exceed the requirements and specifications for conventional roads. These include advance guide signs for interchange exits, supplemental signs, exit direction signs, diagrammatic signs and several other miscellaneous sign types. Refer to the TMUTCD for more information on guide signs for freeways and expressways.
Existing guide signs should be evaluated to determine if they are still applicable for the project. Based on traffic and crash data, the designer should determine the guide signs needed to increase roadway operational efficiency and safety and these signs are shown on the geometric schematic.
4.4.8.2 Preliminary Illumination Locations
Preliminary illumination locations should be developed and shown on the geometric schematic. Illumination infrastructure must meet the requirements of the American Association of Highway and Transportation Official’s (AASHTO)
Roadway Lighting Design Guide
and the TxDOT standard equipment and spacing as detailed in the standard specifications and the Highway Illumination Manual
.Electrical systems must be designed in accordance with the
National Electrical Code
. A preliminary illumination layout must be prepared showing pole locations and power sources. Also provide a layout showing the photometry and foot-candle reading.Federal Aviation Administration (FAA) requires notification of construction for above ground level structures planned near airport facilities. Refer to the FAA Obstruction Evaluation/Airport Airspace Analysis (OE/AAA) for more information and the latest required forms.
The department uses two types of illumination systems:
- Continuous illumination systems– Provides continuous lighting of main lanes, direct connectors, ramp entrances and exits, and merge and diverge areas; and
- Safety lighting systems- Provides lighting at interchanges, highway intersections, or other decision-making points of nighttime hazard. The designer determines the need for safety lighting based on geometric hazards, high crash rates, etc.
Preliminary cross-sections, locations of proposed roadside barriers, topographic maps and information on existing luminaire locations are needed before lighting plans can be developed.
Considerations in designing illumination include:
- Install lighting systems on eligible roadways where conditions warrant such installation; and
- Review illumination proposed for residential areas and minimize undesirable impacts on residences.
Determination of the eligibility of the project for illumination and compliance with warranting conditions must be initiated when preliminary illumination locations are established.
4.4.8.3 Intelligent Transportation System Needs
Intelligent Transportation System (ITS) needs should be evaluated and placed on the geometric schematic. ITS uses advanced wireless communications in vehicles and infrastructure to improve safety, mobility, and reduce environmental impact. Real–time data capture and management from vehicles (trucks, transit, cars), mobile devices, and infrastructure improves operating performance of the surface transportation system. Dynamic mobility applications make the system safer, smarter and more economical.
- Traffic Management Centers (TMC)– TMCs manage department ITS equipment. Large metropolitan areas have dedicated facilities, operators, and support staff. Smaller offices are managed by operators with other duties. A TMC works as a central facility with agencies supporting toll collection, vehicular security, enforcement, and safety.
- Dynamic Message Signs (DMS)– Controlled by the TMC. Signs inform motorists of emergency weather hazards, travel-related Homeland Security advisories, or any incidents on the highway. During non-incident times, travel time messages are displayed to assist with congestion management. They give motorists the choice to continue their route or divert to a less congested highway or street.
The District’s Transportation Systems Management and Operations (TSMO) plan should be consulted to determine which ITS elements are recommended.
4.4.8.4 Interstate Access Justification Report
An Interstate Access Justification Report (IAJR) is a comprehensive report that addresses the FHWA Interstate Access Policy Points. For access changes on all Interstates, an IAJR is required to be prepared and submitted for approval by FHWA. Based on the finalized typical sections, horizontal/vertical alignments and intersection evaluation, the need for changes to access can be determined. Regardless of funding, project delivery type (i.e., DBB or DB) or oversight, new or revised access points on Interstate highways must be approved by FHWA.
Revised access is considered to be a change in configuration even though the number of actual points of access may not change.
Generally, any new or revised access to the Interstate system will require FHWA’s review and action, including the following:
- New freeway-to-freeway interchange;
- New service interchanges providing access between a non-freeway local roadway network (arterial, collector, or local road) and the Interstate;
- Modification of freeway-to-freeway interchange configuration, for example, adding new or abandoning/removing ramps, completing basic movements;
- New partial interchanges or new ramps to/from continuous frontage roads that create a partial interchange;
- Modification of existing interchange configuration, such as adding a loop to a diamond interchange;
- Completion of basic movements at partial interchange, for example, completing a partial diamond interchange by adding a ramp;
- Locked gate access, for example, access via locked gates for emergency response;
- Access from the street network to special uses lanes, such high occupancy vehicle (HOV), high-occupancy toll (HOT) or truck only lanes;
- Relocation of a terminal of a ramp to a different local road;
- Changes in operation of managed-lane access to general-purpose access to the Interstate; or
- Relocation of a ramp gore along an Interstate mainlane. (Under some circumstances, if a ramp is shifted within the same interchange configuration, which results in ramp spacing that meets FHWA's design criteria, and/or if the interchange is reconfigured in such a way that the travel patterns change with the same number of access points, coordination would be performed with FHWA to determine if an approval through IAJR is required or some other process/coordination).
Each entrance, exit, “locked gate,” new or modified freeway-to-crossroad interchange inside a TMA (urbanized area with a population > 200,000), ramp, or access to a collector-distributor is considered an access point. FHWA must ensure there is either no or only minimal adverse effect on the operation of the Interstate facility.
“Locked gate” access points on the Interstate system are used in remote areas in special circumstances for emergency management, border patrol, utility, or maintenance forces.
Refer to TxDOT’s IAJR Engineering, Operation and Safety Analysis Standard Operating Procedure (SOP) for additional information regarding the IAJR development, submission and review process. Also refer to TxDOT’s TSAP for discussion on evaluation tools for developing the IAJR.
Early coordination between the District, DES, and FHWA is needed to ensure proper preparation, review and acceptance. IAJR approval is contingent on the quality and adequacy of the process and documentation. Preparation, review and approval of an IAJR is typically
18 months
.If a freeway is planned as a future Interstate, coordinate with DES for IAJR requirements.
All IAJRs must be submitted to DES for review prior to submittal to FHWA. Include this task duration in the project schedule.
IAJR Re-evaluation
The following primary conditions will require re-evaluation of
previously approved IAJRs
:- Change in approved IAJR design concepts:
- Due to environmental impact;
- Due to final design adjustment; and
- Due to design‐build proposal.
- Significant changes in following conditions:
- Traffic;
- Land use; and
- Environment.
- Time lapse before construction:
- If the project does not progress to construction phase within3 yearsof approval.
Final approval of access cannot precede environmental clearance/NEPA completion.
4.4.9 Railroad Coordination
All work on or within 50-ft of the railroad ROW must be coordinated with the railroad owners. Work within 500-ft of railroad ROW should be evaluated by the District Railroad Coordinator to determine if there is any impact (temporary traffic control, preemption, etc.) to the railroad.
TxDOT enters into a
Construction and Maintenance (C&M) Agreements
with railroad companies when planning construction projects which impact railroad right of way. C&M Agreements with railroad companies can take anywhere from 6 months to 2 years
or more to complete. For this reason, it is essential to begin coordination with the railroad as early as possible in the project development process.Routine maintenance projects or projects with minimal impact on railroad right of way use the Maintenance Notification Letter process (Letter Agreement) and do not require the types of agreements and plan sheets detailed in the remainder of the section.
Refer to TxDOT’s
Rail Highway Operations Manual
for more information on timelines and flow charts for obtaining a C&M Agreement on construction projects and information on the Letter Agreement process for maintenance projects.Early coordination with railroad companies is essential to reduce project delivery delays. Depending on the impact to the railroad, the negotiations, plans, and final agreement can take
4 months to 48 years
to complete. Federal Aid Highway Program projects are subject to a compliance audit for railroad agreements completed prior to the project construction authorization date.TxDOT may not perform work within railroad ROW without the proper agreements and certifications.
Add this task to the project schedule.
Approval for new, at-grade railroad crossings is difficult to obtain. Existing at-grade crossings in the project area may need to 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.
Refer to TxDOT’s
Rail Highway Operations Manual
for detailed discussion of preliminary engineering tasks associated with work near a railroad. Considerations for projects with railroads include:- Locate all potential railroad ROW within 500-ft of the project limits;
- Determine existing crossing conditions and traffic control. Investigate the need for railroad-traffic signal interconnection between various signals;
- Identify opportunities to close or consolidate at-grade crossings;
- Obtain train traffic from railroad owners. Inquire into major railroad line improvement plans;
- Obtain approval of clearances for grade separated structures - railroad preference is an overpass that will clear span their ROW at a right angle;
- Develop recommendations for proposed rail-highway crossings;
- A separate design and agreement may be needed for TxDOT utilities such as storm water, ITS, power, etc.; and
- Document all correspondence regarding the design of the railroad features.
Initial railroad coordination must be conducted before selecting a recommended alignment because railroad issues may affect final alternative selection.
4.4.10 Miscellaneous Design
4.4.10.1 Landscape
If the project is in a city with a Green Ribbon Master Plan, coordinate to implement requirements of the project. A Green Ribbon Master Plan provides conceptual guidance to planning and design in cities with populations greater than 100,000. If the project is within a plan, then ensure that the plan policies are incorporated into the design.
A Landscape and Aesthetics Assessment (LAA) is a tool for identifying landscape and aesthetic issues associated with a specific highway corridor segment. A landscape architect must be consulted to prepare an LAA. Procedures involve field observation and participation in or review of public involvement events. The goal is to maximize design flexibility. Refer to TxDOT’s
Landscape and Aesthetics Design Manual
for more information on preparing the LAA.4.4.10.2 Motorcyclist
Designers should consider the safety of motorcyclists in their development of projects. Refer to the RDM, Chapter 20 for specific guidance and motorcyclist design considerations.
4.4.10.3 Transit
Highways and streets must often accommodate transit vehicles as well as passenger cars and trucks. Refer to the RDM, Chapter 22 for specific guidance on the implementation of transit accommodations.
4.4.10.4 Wildlife Crossings
Wildlife crossings are used to mitigate environmental impacts of a project by providing animals a way to safely cross roadways. Refer to the RDM, Chapter 24 for specific guidance on the design of wildlife crossing.
4.4.10.5 Commercial Motor Vehicle Inspection Stations
The need for infrastructure improvements for Commercial Motor Vehicle (CMV) inspection stations should be shown on the geometric schematic. Determination of their location must be coordinated between TxDOT administration and the Department of Public Safety (DPS). DPS provides permanent scales, if needed, and provides operators for inspection stations.
The need for “weigh-in-motion” (WIM) detectors and locations are determined by TPP - Freight and International Trade Office. These detectors are used to gather vehicle information not for law enforcement.
Construction of new inspection stations must be authorized by TTC minute order. The District should clarify funding for the planning and design of such improvements.
Projects that serve existing inspection stations must consult DPS for needed infrastructure improvements as part of the project.
4.4.11 Design Exceptions, Waivers, Variances or Deviations
Prior to the Final Design phase of project development, the need for a design exceptions, waivers, variances or deviations should be identified.
- Design exception–required when existing or proposed design elements do not meet the minimum values of controlling criteria shown in the RDM. A design exception is not required when values exceed the minimum guidelines.
- Design waiver– required when minimum values of TxDOT’s non-controlling criteria as outlined in the RDM are not met.
- Design variance- required to be sent to the Texas Department of Licensing and Regulation (TDLR) whenever the design guidelines specified in the Texas Accessibility Standards (TAS) Public Rights-of-Way Accessibility Guidelines (PROWAG) are not met.
- Design deviation- required for projects that do not meet specified bridge vertical clearance requirements for highways on the Texas Highway Freight Network (THFN).
Form 1002, PS&E Submission Data is the official place where project design criteria are documented. Design exception/waiver/variance/deviation locations and issues are noted on this page with an approval date and authorized District signature.
An explanation of why design exceptions/waivers/variances/deviations are needed must be sent to the District design exception committee for approval.
Documentation of the Design Exception/Waiver/Variance/Deviation Record of Decision must be retained in District design exception files
. Furnish a copy of all documents to the DES when submitting the Ready To Let (RTL) plans submission.Refer to the RDM for additional information on the submission, review and approval process of design exceptions, waivers, variances and deviations.
Tasks to be performed in determining the need for design exceptions, waivers, variances and/or deviations include:
- Identify design exceptions/waivers/variances/deviations;
- Thoroughly document why design exceptions/waivers/variance/deviations are needed;
- Evaluate the safety, operational and other impacts of the proposed and alternative designs;
- Prepare design exception/waiver/variance/deviation requests;
- Process design exceptions and waivers at the District level;
- Submit Interstate design exception requests to DES Project Delivery Section (refer to the Design Exception Request for Interstate Highways TxDOT SOP);
- Submit design variance requests to TDLR for review and approval;
- Submit THFN design deviation request to DES – Project Delivery Section for review and approval;
- Document approved design exceptions/waivers/variances/deviations on Form 1002;
- Obtain District or FHWA approval of design exception/waivers/variances/deviations requests or revise schematic or plans; and
- Identify and submit additional design exceptions/waivers/deviations as the project progresses.
4.4.12 Constructability Review
Requirements for construction, including construction phasing, must be considered throughout development of the geometric schematic. Identifying constructability issues reduces change orders and delay costs and results in less inconvenience to the traveling public. Future maintenance problems may also be eliminated. Use of 3D modeling can help provide a view of construction conflicts and
may be required for FHWA FAHP projects greater than one million dollars
.A multi-disciplinary review team should conduct the constructability review as it relates to areas of maintenance, traffic, design and construction. The review team should review requirements for access and operation of construction equipment to ensure that the geometric design can be built.
Safety of the traveling public and construction workers is a primary focus of the constructability review.
4.4.13 Cost Estimate Updates
Construction and ROW cost estimates, and corresponding TxC data, must be updated periodically to reflect project changes. Typically cost estimates are updated at milestone deliverables, however, the cost may need to be updated more frequently depending on the project’s development schedule.
Any cost overruns will affect District programming of projects and must be identified as early as possible and shared with District planning/funding staff. The cost estimates must accurately identify approved funding sources (federal, State, and local participation).
Some categories of funding will require approval for changes to the estimate. Coordinate with the funding category’s funding manager prior to updating estimates.
Use TxDOT’s CCEG and CCEG spreadsheet tool to develop the cost estimate for each geometric schematic submittal. Eligible utility adjustment costs must be included in the ROW cost estimate.
If updated estimate total cost meets or approaches the VE threshold, consider conducting a VE analysis (see
.)
4.4.14 Geometric Schematic Layout Development
Typically, the geometric schematic layout is developed with multiple milestone submittals (e.g., 30%/60%/90%/100% or Preliminary/Final). The District may reduce or add interim milestone submittals as deemed reasonable.
4.4.14.1 District Review of Geometric Schematic
The geometric schematic must be reviewed by a multi-disciplinary District review team at milestone submittals. The geometric schematic is made available for review and approval according to the District’s schematic review process.
Suggested SME reviewers include, but are not limited to:
- Area Office;
- District Design;
- Drainage;
- Environmental;
- ROW/Utilities;
- Structures;
- Survey; and
- Traffic Engineering.
All review comments from the District review team should be documented and addressed in the Schematic QC Checklist.
4.4.14.2 Geometric Schematic Review with Stakeholders
Stakeholders must be kept involved throughout project development. When local entities, MPOs, and LG officials are stakeholders in a project, it is advisable to obtain their review and input on the schematic during development. The review will allow for discussion and consensus building on decisions and can be useful if project changes involve significant funding changes. The PM should ensure that all public comments are captured and addressed.
4.4.14.3 Geometric Schematic
At the District’s discretion, another public meeting may be conducted if desired. The public meeting should be conducted as described in
and
. If desired, other effective outreach methods can be conducted in place of or in addition to a public meeting. Consult with TPP - Public Involvement Section and TxDOT’s statewide
Strategic Public Engagement Guidance
.4.4.14.4 Revise Design if Needed
Based on stakeholder input from the public meeting and local entities’ review of the project, the geometric schematic design may need to be revised. If the design and/or layout is revised, the District’s review team should review the revised materials.
Ensure that all public comments are captured and addressed. Consult with the TPP – Public Involvement Section on ideas for closing the “feedback loop” with the public and stakeholders to demonstrate how the project team responded to public comments.
Substantial changes in design may require additional environmental studies and/or documentation. Coordinate all changes with the District Environmental Coordinator.
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