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Planning Studies

Planning Studies are conducted on state highway facilities and developed to identify deficiencies and propose solutions. These studies are part of the Washington State Department of Transportation's (WSDOT) long range planning program and are intended to support local jurisdictions in implementation of the Growth Management Act (GMA) Revised Codes of Washington (RCW) 36.70A.

A set of activities performed at WSDOT regional planning offices and headquarters, as well as Metropolitan Planning Organizations (MPOs), Regional Transportation Planning Organizations (RTPOs), to identify transportation deficiencies and conceptual solutions. These studies are conducted at the statewide, regional, sub-area, corridor or route levels.

It is important to realize that planning studies vary significantly in content and coverage, restricting the ability to more narrowly define the term. It is during this early project definition stage where a project is born. However, the planning study results in a concept that needs further scoping and design to develop into construction project ready for delivery. This early project definition affects later development elements such as programming and project development. It is important to note the relationship that exists between the various levels of plans and studies. Some studies are the direct result of a state or regional plan that highlights a deficiency within a particular area or corridor.

Planning Studies List and Statewide Map of Studies

The Statewide map of studies currently online show individual counties where the user can select a county for more detail, or select a study off the statewide map.

  • Dots are shown midpoint of the study milepost limits.
  • If a county is selected and the dot for a study in the drop-down box does not show, this means the study crosses county boundaries and the midpoint of that study is in an adjoining county.  

Corridor Planning Study Process

The Corridor Planning Study process integrates various elements to produce an endorsed highway design solution. This process identifies transportation services desired by WSDOT customers, determines competing demands, and integrates the findings into a common vision for the entire transportation system, and supports investment decisions.

The process involves the following phases:

  • Identify study area
  • Establish goals and objectives
  • Data collection (inventory)
  • Public meetings
  • Interagency liaison
  • Traffic analysis
  • RDP proposals (alternatives)
  • Review comments
  • Implementation
  • Evaluation

As a guideline, endorsed Corridor Planning Studies provide the following:

  • Guidance for regional decision makers regarding future projects on state routes
  • Direction in determining impact mitigation measures for proposed developments
  • Inclusion of improvement solutions in the State Highway System Plan (18 mb)
  • Guidance for interim projects to ensure the progression towards long range objectives
  • Coordination with various stakeholders on the future development of the state route


Study Types Available

Corridor Management Plans

Corridor Management Plans provide analysis of a corridor over a 20+ year planning horizon. CMPs are developed in coordination with the USDOT/FHWA Scenic Byway program. These plans follow FHWA guidelines for a master planning process along a corridor, with a focus both within and outside of the highway right-of-way. These plans establish community-based goals and implementation strategies along a corridor and describe how to use community resources efficiently, how to conserve natural qualities of the corridor, and how to enhance its value to the community.  more information... 

Corridor Study

The usual purpose of the corridor study is to determine the best way to serve existing and future travel demand. These studies define alignment, mode(s) and facilities between activity centers or other logical termini. Corridor planning is accomplished using a long-range outlook (at least 20 years, but sometimes longer).  more information...

Design Analysis

Design Analyses are conducted when the level of detail in a normal scoping process is not adequate to develop a solution and associated cost estimate for a specific situation. The design analysis provides a level of detail that identifies enough of the construction details to determine the feasibility of the solutions and to provide a close approximation for cost estimating purposes. Design analyses are usually done for projects that are expected to go to design in the upcoming biennium. But design analyses can also provide information for right-of-way preservation and for future projects.  more information...


Route Development Plans

Route Development Plans (RDPs) are planning studies on state highway facilities, developed to identify deficiencies and propose solutions. These plans are part of the WSDOT long range planning program and are intended to support local jurisdictions in implementation of the Growth Management Act (GMA) Revised Codes of Washington (RCW) 36.70A. RDPs are now called "Corridor Planning  Studies."

Environmental Assessment

Environmental Assessments are used to evaluate a projects environmental impacts prior to construction. These studies may be a precursor to an Environmental Impact Study (EIS). Their purpose is to determine simple mitigation measures that may be employed to reduce these impacts. These studies terminate with findings at their completion of either no significant impact, or require the completion of an EIS to study the issues in more detail and to address environmental concerns.

Environmental Impact Statement

An Environmental Impact Statement is environmental analysis required under the Federal National Environmental Policy Act (NEPA) and/or the State Environmental Policy Act (SEPA) when a project has probable significant adverse environmental impacts.

Border Crossing

Border Crossing studies are conducted to explore transportation and related economic issues that may arise between the State of Washington and other adjacent jurisdictions such as British Columbia, Oregon and Idaho. Most studies in Washington have addressed freight and economic issues between Canada and the USA that have occurred because of the NAFTA agreements.

Alternate Route Analysis

Alternate Route Analysis studies are conducted when an existing route may need realignment due to capacity or other constraints where further improvements of the route may be prohibitively expensive or impossible to construct. These studies generally explore the development of new state routes that would bypass urban congested areas.


Major Investment Study

Major Investment Studies were developed as part of the Intermodal Surface Transportation Efficiency Act (ISTEA) Act of 1990. Their purpose was to explore a number of potential lower cost solutions to a highway transportation problem to determine if less expensive solutions could solve transportation problems in lieu of an expensive expansion construction program. The benefits of the lower cost improvements are compared with those of the more expensive construction solutions for cost effectiveness.

Special Study

Other types of studies that are conducted for a special purpose but do not fall into the Corridor or Route Development Plan categories can be described as "special studies" and include:

Interchange Justification Report

This report is used to justify and document a new access point or access point revision on limited access facilities. WSDOT follows the FHWA policy on access to the interstate system, which was developed to ensure that new or modified accesses are properly reviewed and the highest level of service in terms of safety and mobility can be maintained. An interstate IJR is approved by FHWA, while a state route IJR is approved by WSDOT HQ.

Spot or Location Studies

These types of studies often come about through special legislative or political interest, or even through special operational funding. Select, targeted funding is provided to address specific problems or deficiencies, similar to feasibility studies. Often, spot studies address safety issues (due to conditions causing a high number of accidents), address intersection improvement, signalization, or traffic improvements with interconnects to the highway system. Spot or location studies may vary and results range from recommending a course of action, proposing a future solution coupled with immediate short-term delivery fixes, or even identifying an appropriate alternative solution.

Sub-Area Studies

The primary purpose of the sub-area study is to support investment decision making in a financially constrained environment. The study area is what can be described as a transit center where most travelers have more than one choice of travel route or mode of travel to connect to trip end points.


Other Studies

These studies may include such things as the economic benefits of building a new highway (for example - SR 504 Mount St Helens Highway Extension).

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Biennium - An accounting period of 25 months, used by WSDOT and the State, which starts July 1st of the odd year and ends on June 30th.

Scoping - the first step taken in developing a project estimate. It is a detailed look at need for the project, possible environmental impacts, roadway design matters, and stakeholder issues.

FHWA - FHWA became a component of the Department of Transportation in 1967 pursuant to the Department of Transportation Act (49 U.S.C. app. 1651 note). It administers the highway transportation programs of the Department of Transportation under pertinent legislation and the provisions of law cited in section 6a) of the act (49 U.S.C. 104) The Administration encompasses highway transportation in its broadest scope seeking to coordinate highways with other modes of transportation to achieve the most effective balance of transportation systems and facilities under cohesive Federal transportation policies pursuant to the act. The Administration administers the Federal-Aid Highway Program; is responsible for several highway-related safety programs; is authorized to establish and maintain a National Network for trucks; administers a coordinated Federal lands program; coordinates varied research, development and technology transfer activities; supports and participates in efforts to find research and technology abroad; plus a few additional programs.

Growth Management Act - (RCW 36.70a and RCW 47.80). Adopted in 1990 and all associated amendments since that time. Passed by the state legislature in 1990, and amended in 1991, GMA addresses the negative consequences of unprecedented population growth and suburban sprawl in Washington. The GMA requires all cities and counties in the state to do some planning and has more extensive requirements for the largest and fastest-growing counties and cities in the state. Its requirements include guaranteeing the consistency of transportation and capital facilities plans with land use plans.