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Design Criteria
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Technical Memorandum
To: File
From: Anna Ly, PE
Copies: Lori McFarland, PE
Date: July 13, 2018
Subject: May Creek Trail Design Criteria
Project No.: 32978
The purpose of this technical memorandum is to present the proposed design criteria that will be used to develop
the May Creek Trail extension in Renton, Washington. The trail extends the existing trail from the west side of
Interstate 405 to Jones Avenue NE at milepost 7.2, as shown below.
The trail will be on lands owned by the City of Renton or WSDOT, affecting which design standards apply to the
project. Maintenance will generally be performed by the City of Renton.
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May Creek Trail Design Criteria July 13, 2018
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Design References
1. United States Access Board – ABA Standards Chapter 10: Recreation Facilities
Section 1017 Trails
Section 1019 Conditions for Exceptions
2. City of Renton – Trails and Bicycle Master Plan (TBMP)
3. WSDOT Design Manual
Chapter 1515 – Shared-Use Paths (Dated: _July 2014_)
Applicable Standards
Per the City of Renton Trails and Bicycle Master Plan, the May Creek Trail will be a soft-surface hiking only trail.
Pertinent standards taken from the US Access Board ABA Standards are as follows:
Slopes:
Not more than 30% of the total length of a trail shall have a running slope steeper than 1:12 (8.33%). The
running slope of any segment of a trail shall not be steeper than 1:8 (12%).
Where the running slope of a segment of a trail is steeper than 1:20 (5%), the maximum length of the
segment shall be in accordance with Table 1017.7.1, and a resting interval complying with 1017.8 shall
be provided at the top and bottom of each segment.
The resting intervals shall be 60 inches long minimum.
Where resting intervals are provided within the trail tread, resting intervals shall be at least as wide as the
widest segment of the trail tread leading to the resting interval.
Resting intervals shall have slopes not steeper than 1:48 in any direction.
Table 1017.7.1 Trail Running Slope (Grade) and Resting Intervals
Running Slope of Trail Segment Maximum Length of Segment
Between Resting Intervals Steeper Than But Not Steeper Than
1:20 (5 percent) 1:12 (8.33 percent) 200 feet (61 m)
1:12 (8.33 percent) 1:10 (10 percent) 30 feet (9 m)
1:10 (10 percent) 1:8 (12 percent) 10 feet (3050 mm)
Cross Slope: The cross slope shall not be steeper than 1:48 (2 percent).
WSDOT Design Manual – Shared-Use Paths
Side Slopes & Pedestrian Rail:
Where a shared-use path is adjacent to a vertical drop of 2 feet 6 inches or more, a pedestrian rail is
needed.
Where a vertical drop is less than 2’-6”, a pedestrian rail, chain link fence or 4” curb at the edge may be
installed to delineate the edge.
Embankment side slopes of 6H:1V or flatter provide a gently sloping path border.
For side slopes steeper than 3H:1V, evaluate potential risk and provide mitigation.
A minimum 5-foot separation from the edge of pavement to the embankment edge.
A natural barrier such as dense shrubbery on the side slopes.
A physical barrier, such as pedestrian rail.
Clearances:
The minimum horizontal clearance from edge of pavement to an obstruction is 2 feet. Provide minimum
vertical clearance of 10 feet from pavement surface to overhead obstructions.
Conceptual Cross Section
Based on the above standards and matching the existing trail, the cross-sections below are recommended
with the exception that the trail should be 8 feet wide within WSDOT right of way.
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May Creek Trail Design Criteria July 13, 2018
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Signage
Signage is not required by any of the design references but it would be advisable to place a small wayfinding
sign on Jones Avenue NE to denote the trail.