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HDS Instructions

The highway designer provides the draft HDS form or a waiver during the 30% design activities.  The instructions below provide guidance for completing the form.  For a more detailed discussion on the theory behind and proper use of the HDS form, see PDDM Section 9.1.3.

Project Information

  • Project Number – Provide the project number as found on the Project Management System;
  • Project Name – The project name can be found in the Project Management System.  If needed, obtain this information from the PM or HDM;
  • Location – Identify the Park/Refuge/Forest, etc.  In addition, identify the county and state where the project site(s) are located;
  • Route – Provide both the route name and route number (if you have more than 1 route on a project, click on the button that says “add another page” at the bottom of the sheet and a duplicate first page will appear.  Route names and numbers can typically be obtained from the RIP Reports for NPS and NWR projects;
  • Type of Project – Select from the dropdown menu either new construction, reconstruction, 3R (resurfacing, restoration, or rehabilitation), or other (for any other type of project);
  • Terrain – Select from the dropdown menu either level, rolling, or mountainous. Refer to PDDM Section 9.3.1.3 for additional information.
  • Description – Briefly describe the work included in the project. This description should be similar to what is shown on the Title Sheet of the plan set.  The description should state what is being changed or improved on the project.  For example, “Reconstruction of approximately 0.3 miles of Big Fork Athens Road. The road will be realigned and widened to meet County Road standards. The work includes grading, aggregate base, drainage, retaining walls, guardrails, paving, and other miscellaneous work”;
  • National Highway System - Check the box if the project is on the National Highway System (NHS).  Use the NHS Maps to verify if the project route is on the NHS;  
  • Owner/Maintaining Agency – Indicate whether the highway is on a National Forest, National Park, or another system. List the maintaining agency if different from the owner;
  • Functional System – Select from the dropdown menu using the AASHTO Green Book, AASHTO Low-Volume Roads, or Park Roads Standards manual for guidance.  If you select “National Park Roads” or “Low Volume Roads” from the list, another box will appear on the form for the selection of the functional subsystem from the Park Roads Standards or Low-Volume Roads standards.  You can also check the scoping report or confer with your HDM if you are unsure.  You can also refer to the PDDM Section 9.3.1.2 for more information. 

Traffic Data Table

See PDDM Exhibit 8.6-A for more information.

  • Current Year – Enter the scheduled project award year, not necessarily the current calendar year; 
  • Future Year – Enter the design year, typically based on roadway pavement life expectancy.  For asphalt paved roads, typically use 20 years in the future from the project award year.  For concrete pavement (PCCP), use 35 years.  For gravel-surfaced roads use 10 years.  For pavement preservation projects use 5 years.  See PDDM Section 11.2.1.1 for additional guidance.  The traffic data for the design year is projected with an assumption of 1.5 to 3.0 percent growth per year unless a more accurate projection exists;
  • Annual Average Daily Traffic (ADT) – Typically provided by Land Management Agency (LMA); 
  • Seasonal ADT (SADT) – Provide an SADT when a high visitation season exists, if data is available.  Otherwise, leave blank; 
  • Design Hourly Volume (DHV) – Provide the actual traffic count if available.  If not available, use 0.15 x SADT (or use ADT if SADT is not available).  This number should not exceed the theoretical capacity of the road;
  • Percentage Truck Traffic – This is the percentage value of trucks compared to the overall traffic.  Use the default value of 5% for urban areas and 10% for rural areas unless project-specific data is available; 
  • “D” factor – Use the default value of 0.55 unless project-specific data is available;

Design Standards

Document the source for the design standards used in the project by checking the appropriate box (refer to PDDM Section 4.4).  If more than one design standard is used, check all applicable boxes.  For FLH, the applicable design standards typically depend on the Partner agency and/or ADT of the route, as illustrated below.  Consult with your HDM if you are unsure:

  • AASHTO Green Book – Use to identify the design standards on all projects with ADT greater than 2000 unless noted below;
  • AASHTO Low Volume – Use to identify the design standards on all projects with ADT less than 2000 unless noted below; 
  • Park Roads Standards – Use only on NPS projects and only for design speed, lane width and shoulder width design standards ; use the AASHTO Green Book or the AASHTO Low-Volume Roads manual (ADT<2000) for all other design standards;
  • State Road Projects – If a state standard is to be used, check the "State" box and replace that text with the local state standard used;
  • Other Design Standards – Check the box and replace the text with the “other” standard used, such as a local county or city design standards, or USFS Manual.

Design Criteria Table

For design speed, there are two criteria: ‘Minimum from Standard’ and ‘Chosen for Segment’.  For the ‘Minimum from Standard’ box, input the minimum design speed in accordance to the design standards reference manual used and the applicable roadway classification.  For the ‘Chosen for Segment’ box, input the design speed chosen for use on “this” project.  The ‘Chosen for Segment’ speed is the “design speed” for the project, and will drive the selection of all remaining design criteria on the form. 

Using the appropriate design standard reference manual, list the remaining design criteria that apply to the project in the ‘Standard’ column. If a criterion does not apply to the project (e.g. bridge criteria on a project without a bridge), insert N/A. It is also recommended to include for the benefit of the reviewer, the reference document used for the standard in the “exception” column, including the table or the page number where the standard was located.

The design criteria used on the project are listed in the “As Designed” column, and design exceptions are listed in the “Exception” column.  For example, if the minimum curve radius is not met for a given location, the substandard radius actually used would be placed in the “as designed” column.  For projects where the existing geometry is incorporated into the final design without any changes, such as some 3R projects, document the known information as much as possible. When the existing information is not known, indicate that the project geometry matches the existing conditions.

If the selected design speed is under 50 mph, the document will automatically change the display to show possible exceptions only for the design speed and design loading structural capacity, and to show “Variance” heading of the third column for the remaining 8 criteria instead of “Exception”. Fill out the “Variance” column with concise information on why the standard cannot be met (such as that to bring the design up to standards would require disturbance that is outside of the scope of the project, etc.).  In addition, select the checkbox in the last column if an exception or variance to the design criteria has been applied.

Justification of Design Exceptions and Variances

Provide a narrative describing any design variances or exceptions and reasons why a design variance or exception is needed. Give reasons why the design standard should not be met in the proposed design and provide support to justify the proposed design criteria. If needed to support the justification, document the estimated costs to achieve the design standard and the estimated cost of the proposed design exception. 

Considerations which may warrant an exception to the design standard include:

  • Social, economic, and environmental impacts
  • Steep terrain
  • Compatibility with adjacent sections on a route
  • Excessive construction cost
  • Right-of-way constraints
  • Impacts during construction, including traffic control operations, detours and private property access
  • Visual impact
  • Geotechnical infeasibility
  • Relationship to future improvements

In addition to describing why the exception is needed, explain the alternatives considered and risks associated with accepting the design exception.  In addition, identify anything which is being done to mitigate the risks in lieu of meeting the standard. 

For example, if a horizontal curve cannot meet the standard, justification might be related to the economic and environmental impacts necessary to bring the curve up to standard.  The risk would be drivers not expecting the substandard curve and driving too fast for the substandard conditions.  The mitigation provided in lieu of meeting the standard could be placing advance curve warning signs and delineators along the outside edge of the curve. 

Review, Approval, and Distribution

Submit a draft HDS form at each preliminary design project milestone. Present the completed form for signature, preferably at the 70% project milestone, but no later than the 95% milestone. Obtain signatures as noted below:

HDS Approval Process
DivisionIn-House DeliveryA/E Delivery
WFLDesigner
Highway Safety Engineer*
Highway Standards Engineer
Highway Design Branch Chief
Partner
Chief of Engineering
A/E Lead Designer
Highway Safety Engineer*
Highway Standards Engineer
Highway Design Branch Chief
Partner
Chief of Engineering
CFLLead Designer
Highway Design Manager
Project Development Branch Chief
Partner
Chief of Engineering
A/E Lead Designer
A/E Manager
Project Manager
Project Development Branch Chief
Partner
Chief of Engineering
EFLDesigner
Highway Design Manager
Highway Design Branch Chief
Partner
Chief of Engineering
A/E Lead Designer
Highway Design Manager
Highway Design Branch Chief
Partner
Chief of Engineering

* Route to the Highway Safety Engineer for review, but signature is not required.

If any design changes occur after 70% that would be reflected in the HDS form (including design criteria, justification, or mitigation), revise the form and obtain signatures on the updated form. Attach the original form to the revised form to maintain documentation of design decisions.

Distribute and store the completed HDS form according to division procedures.

Updated: Monday, May 18, 2020