Design guidance for planning studies

Consider priority design issues in the planning phase to reduce or redirect efforts during scoping and design.

The priorities and level of detail during the planning phase will differ from those in the design phase. Balance extra time spent at any one location against the odds of timely or eventual funding. This guidance will help you maximize your efficiency.

Getting started

Before starting the planning study, check out the WSDOT Design Manual Chapters 1100 through 1106, and 1500 through 1520. These include procedures, terminology and documentation requirements to bear in mind during the planning phase.

Design information & planning priorities

During planning, the process for examining design issues is normally limited to information that boosts agency and stakeholder understanding of the project development process due to the future funding uncertainty of resulting projects. Studying and documenting design issues raised by staff and stakeholders during a planning study can help resolve many issues that come up later in the design phase.

The common design elements to consider and document in a planning study include:

  • Performance metrics.
  • Baseline and contextual needs.
  • Context and modal accommodation.
  • Design year.
  • Intersection design vehicle.
  • Terrain.
  • Access control.
  • Target speed.

Note: This list does not include all design-related information considered at the project level.

Performance metrics

Establish performance metrics to guide protocols for design-level decisions in your planning study.

For example: Use “vehicle level of service” to select a transportation strategy that addresses a target performance metric. The designer would then use that same metric to select and refine a solution using the documented performance areas of interest, metrics and targets based on the guidance on this page.

Baseline & contextual needs

A highway’s transportation needs relate to its use, the types of travel involved and any existing established service level thresholds. The transportation needs identified during planning should help shape the strategies documented in the plan. Without an identified project, the definitions of baseline and contextual needs differ slightly from those used at the design stage.

Baseline needs

  • Planning stage - Issues staff determine would most likely drive strategies related to the study purpose and need.
  • Design stage - Issues that must be addressed by the project and play a key role in the project definition.

Contextual needs

  • Planning stage - Other remaining issues that come up during the planning process and help shape expectations of the strategies at the project stage. Focus on documentation of lower cost contextual needs associated with known agency priorities and programs with consultation of related subject matter experts.
  • Design stage - Remaining issues that are most commonly used to improve the project at low or no cost.

When considering baseline and contextual needs, limit the level of detail to what is needed to inform the creation and description of any strategies identified to address them.

When preparing baseline and contextual needs, refer to and summarize the analysis performed by those systemic programs that apply within the study area. This summary is similar to those provided in Corridor Sketches, though it is localized to the study area. If the planning study is intended to analyze or otherwise solicits strategies related to these systemic programs (safety, preservation, environmental, etc.), any data collection, analysis, and solicitation should take place within the context of the systemic process defined by the program(s), with the intention of complementing and informing program prioritization or related processes.

Context and modal accommodation

We use a context classification system at the design phase to help select modal priorities. The tools and the output used in this process can transfer to most planning work. You can also apply the results to track information about planning-level decisions related to the demand for different types of travel in the corridor.

More information

WSDOT Design Manual Chapter 1102 and 1103 and the Context and Modal Accommodation Report (CMAR) template have more information about procedures and documentation requirements.

Document in the plan the context classification and modal accommodation levels identified for the corridor under consideration. Where context is changing over the length of the corridor, perform a separate exercise and document the results for each contiguous portion. If the number of changes exceeds the resources available to perform the work, make simplifying assumptions to expedite the work or exclude portions where an assumption of modal priority may be obvious.

Local planning horizon year

Use the "local planning horizon year" used in demand and/or operations modeling instead of "design year". If a project is later identified and funded, this planning horizon year becomes a starting point for documenting if and how changes in planning assumptions should move forward.

Intersection design vehicle

Intersection designs are particularly dependent on two related procedures:

  • "Design for”: The vehicle is expected to stay in the travel lane because the volume of the vehicle suggests it will be a common occurrence.
  • “Accommodate”: Expects vehicles to sometimes leave the travel lane during a trip.

Common large vehicles are associated with freight and include single and combination units. There are no set thresholds for “common”, so document your reasoning behind which types of large vehicles you will design for, and those that will be accommodated for (because although not common, they can be expected).

Investigate the types and quantities of large vehicles and the places they are coming from and going to that are associated with need for turn movements at corridor intersections. Vehicles carrying the public and students may also be present. Pedestrians can be a competing interest, since designing for large vehicles usually increases crossing distances.

More information

See the WSDOT Design Manual Chapter 1310 for definitions of the different design vehicles.

Terrain

The terrain classification refers to certain geometric information during design, such as maximum grade and curves. The designations can help set expectations among staff and stakeholders during the design phase.

More information

the WSDOT Highway Log.

Access control

The access control classification sets expectations for design issues related to managing the different means of travel on the corridor. These issues can include demand for turn lanes, curb cuts, drainage and medians.

Find more specific information

Proposed target speed

We use a target speed approach to determine the design speed. A “proposed target speed” meets context and facility-user expectations by setting the same posted, design and operating speeds. It provides a good starting point in case a project is identified and funded for design. The actual adoption of the target speed happens during the design phase and requires input and approvals from various region and HQ design and traffic staff.

Before selecting the proposed target speed, engage the public, local agency staff and officials, and transit agencies. Use the table below to select an initial target speed.

Document the target speed chosen during planning as the “proposed target speed.”

Low speed (35 mph and below)

A low target speed is ideal for roadways with pedestrian and bicycle modal priorities. Locations that include frequent transit stops, intermodal connections, moderate to high intersection density, or moderate to high access densities may also benefit from lower speed environments. Low speed facilities in urban areas typically use narrower cross section elements.

Intermediate speeds (between 40 mph and 45 mph)

An intermediate target speed is ideal for speed transitions between high and low target speed environments. Locations with low access densities and few at-grade intersections are also examples of where intermediate speed may be appropriate. In these locations consider a higher degree of separation between motor vehicles and bicycles and pedestrians.

High speed is (50 mph and above)

A high target speed is ideal for motor vehicle- oriented roadways such as freeways and highways, often serving regional or longer-distance local trips. Rural connector roadways with infrequent farm or residential accesses are also consistent with the use of high target speeds. In high target speed locations consider the highest degree of separation between motor vehicles and bicycles and pedestrians. Highways with high speeds are associated with wider cross section elements.

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