Find state roadside safety policies and guidance for designers in Division 16 of the WSDOT Design Manual.
Before using these chapters, designers need to see WSDOT Design Manual Chapter 1105 (PDF 127KB) (for Improvement projects) or Chapter 1120 (PDF 97KB) (for Preservation projects) to determine what kind of roadside safety design and analysis are required on your project.
Design Manual M22-01
Chapter 1600 Roadside Safety (PDF 678KB)
Chapter 1610 Traffic Barriers (PDF 1.2MB)
Chapter 1620 Impact Attenuators (PDF 1.8MB)
Design Bulletins about roadside safety are occasionally issued to provide clarification or additional guidance for certain situations or projects types. They are normally provided between manual updates, and eventually incorporated into the WSDOT Design Manual or retired depending on the topic. See the Roadside Safety questions and answers (DOCX 22KB) that specifically addresses emergent questions in roadside safety.
Standard Specifications M41-01
Chapter 8-11 Guardrail (PDF 1.1MB)
Chapter 6-10 Concrete Barrier (PDF 2.3MB)
Chapter 8-17 Impact Attenuator Systems (PDF 1.1MB)
General Special Provisions
Section 8-11 High Tension Cable Barrier (PDF 399KB)
Section 8-11 Guardrail (W-beam with aesthetic treatment) (PDF 399KB)
You can use the applicable standard specification or GSP to search the WSDOT Qualified Products List to determine which roadside safety related proprietary devices are available to meet your design requirements. Our Design Office and Materials Lab updates this through correspondence with manufacturers, particularly with respect to our ongoing effort to implement MASH compliant roadside safety products.
Note: We have other specifications and GSPs that reference roadside safety not shown in the list above but that also commonly apply to projects.
Roadside safety is an important component of total highway design that addresses the area outside the roadway. As described in the WSDOT Design Manual, an intentional approach to roadside design can reduce the severity and subsequent consequences of a vehicle roadside encroachment.
Whenever possible, a designer should design relatively flat, unobstructed roadsides to provide a forgiving environment to an encroaching vehicle. However, designing clear, flat, roadside areas is not always feasible as projects may have competing needs and tradeoffs to consider. Some different factors that may compete with providing a clear, flat roadside area include existing topography considerations, right of way constraints, environmental constraints or other various facilities and project needs.
Roadside Safety training
Headquarters Design holds annual roadside safety training classes (See WSDOT Learning Center, Class: DES: ROADSIDE SAFETY). The classes are open to anyone that is interested.
If you cannot attend an annual class in person, the classes are recorded and can be accessed via the WSDOT Learning Center, Class: DES: ROADSIDE SAFETY
MASH implementation
The Manual for Assessing Safety Hardware (MASH) updated the testing criteria for crash testing roadside hardware. The WSDOT Design Office policy staff are responsible for developing the criteria, guidance, and policies related to MASH transition for design. This work includes criteria for the acceptance and design of MASH compliant roadside safety hardware. WSDOT’s transition to MASH is organized by the Design Office according to stipulations provided in the AASHTO-FHWA Joint Implementation Agreement for MASH.
The transition to MASH is organized by hardware product category. Expect to find updates to the WSDOT Design Manual, Standard Specifications, GSP’s, Standard Plans, and Qualified Products List over time that reflects this transition. Although the last official MASH implementation date has passed, the transition to MASH for some roadside safety hardware product areas continues. Recent direction from FHWA and AASHTO—recognizing that not all roadside safety hardware is MASH compliant at this time—is allowing non-MASH compliant hardware to be installed in certain circumstances. The following links provide information that may be useful for designers.
- MASH Implementation at AASHTO
- MASH Implementation at WSDOT (PDF 139KB)
- WSDOT Project Delivery Memo (MASH Implementation) (PDF 1.6MB)
- WSDOT Project Delivery Memo (MASH F-shape barrier) (PDF 1.1MB)
Length of need
Length of need refers to the total length of longitudinal barrier needed to shield a non-crashworthy, fixed object or feature. A length of need calculation is commonly required to determine the configuration of any barrier regardless of type. The length need calculation spreadsheet (XLS 20KB) may be used when calculating the required length of need for a barrier. See WSDOT Design Manual Section 1610.03(5) (PDF 1.8MB) for more information.
Type 31 Beam Guardrail
Type 31 beam guardrail is used in all new installations except in certain circumstances (see (Old) Type 1 Beam Guardrail section below). All beam guardrail systems require either an anchor or crashworthy terminal at their endpoints. In general, a crashworthy terminal is used when a guardrail end is located inside the Design Clear Zone (see WSDOT Design Manual Section 1600.02 (PDF 615KB)) and can be struck head on by a vehicle. An anchor is allowed when the guardrail end is located outside the Design Clear Zone or inside the Design Clear Zone and not subject to head-on impacts (i.e. trailing ends of guardrail runs on one-way roadways). The WSDOT Beam Guardrail Type 31 Buried Terminal Type 2 (Standard Plan C-22.16) is the preferred guardrail terminal since the end of the guardrail run is buried and not subject to head-on vehicle impacts. Shop drawings and additional information about designing and identifying guardrail terminals and anchors from different manufactures, see listed below.
(Old) Type 1 Beam Guardrail
Type 1 guardrail is no longer used in new installations except in intersection radius designs. A primary reason for phasing out Type 1 guardrail is that all configurations of the Type 1 guardrail are not MASH- compliant (PDF 139KB) whereas Type 31 guardrail is MASH compliant.
(Old) Type 1 Beam Guardrail Placement Cases (PDF 140KB) (Removed from Design Manual in 2017)
(Old) Type 1 Beam Guardrail Terminals and Anchors (PDF 11KB)
(Old) Type 1 Beam Guardrail Transitions (PDF 146KB)
When an intersection radius is needed in new construction, it is permissible to use either one of the (Old) Type 1 designs (Placement Case 12 or 13 (PDF 140KB) or the Guardrail Placement Strong Post Type 31 Intersection Design (Standard Plan C-22.42. See the Plan Sheet Library for Type 1 weak post intersection design plans.
Type 20 and Type 21 guardrail
Type 20 and Type 21 guardrail are primarily used in conjunction with Service Level 1 bridges. Type 20 and Type 21 guardrail are TL-2 systems appropriate for speeds 45 mph or less.
See Type 1 Placement Case 14 (PDF 140KB) for use on Service Level 1 bridge retrofit rail systems. Type 20 guardrail is used on the approach and no transition is needed between the Type 20 guardrail and the Service Level 1 bridge rail since they are both weak post systems. A Type 6 transition is used when connecting the Type 20 to a strong post guardrail or a terminal. See the Plan Sheet Library for more information about these designs.
Contact Bridge and Structures for more information about Bridge Service Level 1 retrofits.
Cable barrier
All cable barrier systems that are available for use in new construction are proprietary. New construction requires the 4-strand versions of these systems. See WSDOT Design Manual Section 1610.05 (PDF 1.3MB) for more information.
Concrete barrier
Concrete barrier is available in either precast or cast-in-place configurations. Precast barrier may be anchored or unanchored according to project requirements and desired deflection characteristics (see WSDOT Design Manual Section 1610.03(3) (pdf 615 kb)). High Performance concrete barrier, which are taller, are available for use when required in certain situations (see WSDOT Design Manual Section 1610.03(1)(b) (PDF 1.3MB)).
Versions of these concrete barrier designs are available with drainage scuppers along the base and may be specified where drainage has to pass through the barrier run. Standard plans for scupper barrier are in development and are planned to be available in September 2021. In the meantime, scupper concrete barrier details are available for incorporating into PS&E packages on a project-by-project basis. Contact HQ Design for more information about scupper barrier, and see WSDOT Design Manual Section 1610.06 (PDF 1.3MB) for more information about concrete barrier.
Impact attenuators
Impact attenuators are protective systems that prevent or reduce the severity of head-on impacts with an object or feature by either gradually decelerating the vehicle to a stop when hitting the attenuator head-on, or redirecting the vehicle away from the object or feature when struck on the side. These systems are used for rigid objects or other features that cannot be removed, relocated, or made breakaway. All impact attenuator systems are proprietary items. Use the attenuator selection template (DOCX 23KB) to determine which products are available to meet your project specific constraints.
See WSDOT Design Manual Chapter 1620 (PDF 1.8KB) for more information on impact attenuators and for links to impact attenuator product documents that may be needed for the design at the impact attenuator location (i.e. attenuator foundation requirements, or other).
Type 31 Beam Guardrail terminals and anchors
Buried terminals and non-flared terminals are available for use with Type 31 beam guardrail. The Buried terminal is the preferred terminal. A non-flared terminal can be used where a buried terminal cannot be installed.
Identifying the different guardrail terminals
Review graphic (PDF 1.25KB) that shows terminals used by WSDOT over the years. Some are no longer used, and some new terminals are not shown.
Type 31 Buried Terminal
Buried terminal is the preferred terminal for Type 31 beam guardrail because it eliminates the exposed end of the guardrail. The guardrail is anchored in a backslope that is 1V:3H or steeper and at least 4 feet in height.
Buried Terminal Type 2 is used when the foreslope is as steep as 1V:4H. A more abrupt flare is acceptable after the rail passed the bottom of the ditch. The height of the guardrail is maintained relative to the roadway and a rubrail is used along the exposed portion of the posts, see Standard Plan C-22.16 (PDF 35KB)
Type 31 Non-flared terminal
As of January 6, 2017, Type 31 beam guardrail non-flared terminals are required to be MASH compliant. The following MASH compliant Type 31 beam guardrail terminals are currently listed on the Qualified Products List (QPL):
- MSKT-SP-MGS (TL-3) (PDF 207KB) - Use for all posted speeds
- MSKT-SP-MGS (TL-2) (PDF 198KB) - Use when posted speed is 45mph or less
- SoftStop (TL-3) (PDF 205KB) - Use for all posted speeds
- Softstop (TL-2) (PDF 199KB) - Use when posted speed is 45 mph or less
- MAX-Tension (TL-3) (PDF 330KB) - Use for all posted speeds
- MAX-Tension (TL-2) (PDF 312KB) - Use when posted speed is 45mph or less
The Standard Plans identify proprietary non-flared terminal designs. The Standard Plans do not show all of the details needed to construct these terminals. The Standard Plans supplement the manufacturers drawings which can be downloaded below.
Manufacturer's drawings
For use with 31 inch systems:
- MSKT-SP-MGS (TL-3)(PDF 207KB) - Use for all posted speeds
- MSKT-SP-MGS (TL-2) (PDF 198KB) - Use when posted speed is 45mph or less
- SoftStop (TL-3) (PDF 205KB) - Use for all posted speeds
- SoftStop (TL-2) (PDF 199KB) - Use when posted speed is 45mph or less
- MAX-Tension (TL-3) (PDF 330KB) - Use for all posted speeds
- MAX-Tension (TL-2) (PDF 312KB) - Use when posted speed is 45mph or less
- MAX-Tension Part Number System (PDF 330KB)
The SoftStop and the MSKT-SP-MGS are only supplied with steel posts, but can be used with wood post or steel post guardrail runs.
Type 31 anchors
A guardrail anchor is needed at the end of a run of guardrail to develop tensile strength throughout its length. See Anchor Type 11 Standard Plan C-23.70 (PDF 32KB)
Evaluating existing barrier systems
See Design Manual 1610.03(2) when projects require evaluating existing barrier systems (beam guardrail, concrete barrier, or other) for serviceability. For beam guardrail system serviceability evaluations, use the WSDOT publication Field Guide for Guardrail Condition Assessment (PDF 837KB)
Tim Moeckel, PE
Tim.Moeckel@wsdot.wa.gov
Roadside Safety Engineer
360-704-6377
Kevin Burch, PE
Kevin.Burch@wsdot.wa.gov
Policy Support Engineer
360-704-6381