Chapter 11 — Design Guidance

Statewide design guidance applied with engineering judgment

Chapter 11 provides statewide design guidance applicable to LPA-administered Federal-aid transportation projects. The framing is important: "These guidelines and procedures should be considered in the design of transportation projects and applied with engineering knowledge, experience, and judgment to provide a safe, sustainable, integrated, and efficient transportation system." Design guidance is a floor with flexibility; rigid application without engineering judgment isn't the chapter's intent.

The chapter sits at the intersection of three regulatory regimes:

1. Federal design standards (23 CFR 625, 23 USC §109) — sets what's acceptable for federal-aid geometric design
2. State design standards (Caltrans HDM) — applies on-SHS and recommended elsewhere
3. Local standards — permitted off-NHS with specific governance and signature requirements

The decision of which standard applies depends on:

• Whether the project is on the State Highway System (SHS)
• Whether the project is on the National Highway System (NHS) (but not on the SHS)
• Whether the project is off the NHS
• The type of project (new construction, reconstruction, or 3R)

New/reconstruction, 3R, and bridges — three different standard hierarchies

23 CFR 625 designates the standards, policies, and standard specifications acceptable for application in geometric design. The standards are dependent on the type and location of the project.

Definitions

New construction = building a new facility that did not previously exist — new roadways, alignments, interchanges, grade separation crossings, new parking lots or safety roadside rest areas. The addition of appurtenances (striping, signs, signals, noise barriers) is NOT new construction.

Reconstruction = replacing the entire existing pavement structure with an equivalent or increased pavement structure plus rebuilding adjacent operational and roadside features. Includes:

• Replacement of existing pavement structure
• Addition of a lane (except climbing or auxiliary lanes)
• Significant change in horizontal and/or vertical alignment
• Reconstruction of an interchange by adding moves or relocating ramps (widening for storage, turning, or ramp metering not included)
• Replacement of an entire bridge or major parts (effectively a new bridge)
• Seismic retrofit projects for major or unusual structures (all tunnels, unusual and movable bridges, unusual hydraulic/geotechnical structures, or bridges >125,000 sq ft deck area; or construction cost >$5M per structure)
• Major modifications to Traffic Management Centers

Lane/shoulder replacement typically involves replacing portions of roadway width — that's rehabilitation, not reconstruction. Storm/earthquake damage repairs are not considered reconstruction.

New & Reconstruction by Classification

LPA-developed design standards may be used on off-NHS new or reconstruction projects only if all three conditions are met:

1. Approved by the County Board of Supervisors or City Council
2. Signed by the City/County Public Works Director who is a California licensed Civil Engineer. If PW Director isn't licensed, the LPA's highest level licensed Civil Engineer may sign. Standards may be signed by a consultant on retainer as City/County Engineer if licensed and responsible directly to the PW Director or City/County Manager.
3. Reviewed for possible updating whenever applicable AASHTO standards are updated

3R Projects

Per 23 CFR 625.4(a)(3), geometric design standards for 3R projects on the NHS must be procedures and design criteria established for individual projects, groups of projects, or all 3R projects in a state, as approved by FHWA. 3R is defined as:

• Resurfacing — placing additional hot mix asphalt concrete over a structurally sound highway or bridge needing treatment to extend service life
• Restoration — returning road, structure, or collateral facility to the condition existing after original construction
• Rehabilitation — providing some betterments (upgrading guardrail, widening shoulders)

3R work is "heavy, nonroutine maintenance work designed to preserve and extend the roadway service life for at least ten years and enhance safety wherever reasonable." May include selective improvements to geometry and other roadway features (including safety appurtenances) and still be considered 3R.

Bridges and Structures

All LPA bridge and structure projects must be designed per 23 CFR 625.4(b) in accordance with:

• Current Caltrans-adopted edition of AASHTO LRFD Bridge Design Specifications with California Amendments
• Caltrans Bridge Design Manuals, Policies, Standards, and Guidance

Additional bridge information is in Exhibit 11-B: Bridges and Structures. The chapter doesn't carve out a different bridge standard for off-NHS — all LPA bridges follow the same AASHTO LRFD + Caltrans bridge manual framework.

Caltrans, APWA Greenbook, or LPA-developed

Caltrans Standard Plans are required for all LPA projects on the SHS.

For LPA projects not on the SHS, three acceptable options:

1. Current edition of Caltrans Standard Plans
2. Current edition of Standard Plans for Public Works Construction ("Greenbook") developed by Public Works Standards Inc.
3. LPA-developed standard plans

LPA-developed standard plans may be used on new or reconstruction projects not on the NHS if (same three-pronged test as design standards): approved by Board/Council, signed by PW Director (licensed CA Civil Engineer or LPA highest-level licensed CE), and reviewed periodically.

Caltrans Standard Specs, Greenbook Specs, or LPA-developed

Same pattern: Caltrans Standard Specifications required on the SHS. Off-SHS may use Caltrans Standard Specs, Standard Specifications for Public Works Construction (Greenbook), or LPA-developed standards (with the same three-condition test — Board/Council approval, PW Director signature with licensure, periodic review).

The "year/version" reminder from Exhibit 12-E is critical: always specify the year/version of standards being used in the PS&E to ensure currency.

Delegation of design exception authority — the PW Director\'s desk

The chapter encourages flexible and context-sensitive approaches. Alternatives to design guidance are useful tools — but LPAs must evaluate, approve, and document design decisions.

Projects on the SHS: LPAs must follow PDPM Ch 21 (Design Decision Standards). Accessibility alternatives on SHS projects: Caltrans DIB 82-06 (Pedestrian Accessibility Guidelines for Highway Projects).

Projects not on the SHS (whether on or off NHS): approval of design alternatives is delegated to City and County Public Works Directors.

Design Alternative Process

Fundamental steps:

1. Determining the cost and impacts of meeting the design criteria
2. Developing and evaluating potential consequences and risks of alternatives that may fall outside design guidance
3. Evaluating potential mitigation features
4. Reviewing, documenting, and approving the use of proposed alternatives

Documentation requirements:

• Signed
• Stamped with an engineer's seal
• Approved by the Director of Public Works (or delegate)
• Retained in project files for at least three years from acceptance of final voucher per 23 CFR 710.201(f)

Sample design fact sheet at Exhibit 11-F. A tracking system for design decisions should be implemented by LPAs to retrieve information quickly. Data should include: project description, project location, nonstandard features approved, indication if future commitments have been made.

Bridge Design and Details

LPA proposed bridge or structure design alternatives must follow Exhibit 11-B procedures. Bridge alternatives have their own framework — typically involving Caltrans Office of Structures Local Assistance review.

Signs and Markings

Alternatives to mandatory signs and markings as defined in the California Manual on Uniform Traffic Control Devices (CA MUTCD) may be permitted if a proposal to experiment with non-standard devices is submitted to and approved by FHWA and California Traffic Control Devices Committee prior to implementation. This is a higher bar than other design alternatives — the CA TCD Committee involvement makes it slower and more visible.

Drainage, floodplain, bike/ped, ADA, ITS

Cross drainage, hydraulic, hydrologic design. SHS projects: Caltrans HDM. Off-SHS: HDM recommended; may also reference AASHTO Highway Drainage Guidelines and AASHTO Drainage Manual.

Floodplain Encroachment (23 CFR 650). Two options: follow Topic 804 of HDM, or provide your own Floodplain Evaluation Report following 23 CFR 650 general guidance. SER Ch 17 (Floodplains) has detailed procedures.

Bicycle and Pedestrian Facilities. LPAs encouraged to incorporate non-motorized designs in all activities. Guidance:

• Caltrans HDM Chapters 100, 200, 300, 1000
• AASHTO Guide for Development of Bicycle Facilities
• NACTO Urban Street Design Guide, NACTO Urban Bikeway Design Guide
• ITE Designing Urban Walkable Thoroughfares

Alternatives to bikeway design guidance must meet criteria in Cal Streets & Highways Code §891.

Accessibility and the ADA

State and local governments — regardless of whether they receive federal funds — are required to comply with whichever of the following provides the greatest access:

• Federal 2010 ADA Standards
• Title 24 of the California Code of Regulations (California building regulations)
• Local codes

Private-funded improvements within the public right of way are also required to comply with whichever code offers the greatest access.

If discrepancies are found between federal, state, or local requirements, bring to the attention of the DLAE. Best practice: local entity, State transportation agency, and FHWA work together to come to agreement on reasonable determination, document policies, and apply consistently.

The Alteration vs Maintenance Test (Curb Ramp Trigger)

The single most operationally important content in §11.6 is the alteration/maintenance distinction that determines when curb ramps must be added. Per US DOJ-FHWA joint technical assistance:

DSA Review. Per Cal Gov Code §4454(b)(a): LPA plans and specifications with pedestrian facilities to be constructed with state funds must be reviewed and approved by Division of the State Architect (DSA). For pedestrian facilities within state highway right of way (excluding rail/transit), Caltrans may review and approve in place of DSA. DSA review involves fees paid directly to DSA.

The Accessible Parking and Curb Ramp plans in Caltrans Standard Plans are FHWA-approved for SHS. Refer to current DIB-82 for use of these standard plans.

ITS / Traffic Signal Controllers

Per 23 CFR 940, all ITS projects must adhere to ITS Standards. Choice of standards hinges on Regional ITS Architecture. Cal Vehicle Code §21401:

• Only official traffic control devices conforming to Caltrans-promulgated uniform standards may be placed on a street or highway
• Caltrans newly installed/upgraded traffic signal controllers must be standard protocol capable of two-way communications. LPAs may follow this requirement (not mandatory but encouraged)
• The Legislature encourages LPAs to continue the formerly-mandated action; no liability imposed if LPA doesn't continue