Dear Mayor Cooper and Yarrow Point council members,
WSDOT and Yarrow Point have been partners on the SR 520 Eastside Transit and HOV Project, with the
other Points communities, for many years and we appreciate your commitment to seeing it through.
WSDOT has reviewed Yarrow Point Council Resolution #300 that was introduced and passed at Yarrow
Point council meetings in August. Below is our response to concerns raised in the resolution regarding
safety and construction of the roundabout at 92nd Avenue Northeast.
Section 1: “The Town of Yarrow Point does not support the proposed and designed roundabout
on 92nd Avenue NE, for a number of reasons, including the lack of study and data related to
bicyclist and pedestrian safety.”
Roundabouts are not new to Washington State. We have been building them in Washington since 1997.
Not only are they increasing in number in this state, they are also popping up all across the United States,
and for good reason. They are safe and efficient.
Roundabouts have a demonstrated track record of reducing crashes both nationally and here in
Washington. A national study by the Insurance Institute for Highway Safety showed single lane
roundabouts reduce total crashes by 40 percent and we have seen similar results in Washington State.
Concerns are sometimes raised about the safety of roundabouts for pedestrians and bicycles. There are now
150 single-lane roundabouts in Washington and a review of eleven years of crash data (2000 through 2010)
showed a total of twelve crashes involving pedestrians or bicycles, none of which were serious or fatal.
That equates to slightly more than one per year for all of the roundabout locations combined—a very low
Modern roundabouts are designed to be safer for pedestrians than traditional at-grade intersections.
Vehicles are moving at a slower rate of speed in roundabouts—typically between 15 and 20 miles per hour.
Crosswalks are also set farther back from traffic, allowing drivers more time to react to pedestrians before
merging into or out of the roundabout. Triangular islands between traffic lanes give pedestrians a safe
place to wait if they choose to cross only one direction of traffic at a time.
Experienced bicyclists can choose to ride through the roundabout with traffic or recreational cyclists may
choose to walk their bicycles through the pedestrian crosswalks—much like they would in a traditional
intersection. Like vehicles, cyclists must obey the rules of the roundabout as they proceed through the
Specific pedestrian safety elements in the 92nd Avenue Northeast design include curb extensions and
safety islands between lanes (also called pedestrian medians) to reduce crossing distances; striping changes
so that vehicles stop farther from pedestrian crossings than in a traditional intersection; and signage
alerting motorists to the presence of pedestrians and cyclists.
The design of the 92nd Avenue Northeast roundabout is based on WSDOT’s design manual guidance for
modern roundabouts. This guidance is based on state, federal, national and international guidance and
polices to ensure that our facilities are safe for all users. (See attachments and reference list.)
Section 2: “The Town of Yarrow Point opposes continued construction of infrastructure or other
physical aspects related to the roundabout on 92nd Avenue NE until such time that all of the
Town Council’s concerns, including safety of pedestrians and bicyclists, are fully and thoroughly
As you know, construction is well under way throughout the Eastside corridor and in the vicinity of 92nd
Avenue NE. WSDOT is proceeding with the construction of the lid structure, mainline SR 520 widening,
realigning of the westbound off-ramp, and the regional bicycle and pedestrian shared-use path.
WSDOT appreciates the partnership that we’ve had with the Yarrow Point Town Council and your
residents. Regarding Yarrow Point’s request to redesign the interchange, we will address that request
specifically in a separate letter. We look forward to our continued collaboration as the project proceeds.
SR 520 Bridge Replacement and HOV Program
Washington State Department of Transportation
206-770-3568 direct | 206-770-3500 main
600 Stewart Street, Suite 520 | Seattle, WA 98101
WSDOT information on roundabouts
1. Fact sheet for 92nd Avenue Northeast
2. WSDOT roundabouts brochure
3. WSDOT roundabout information Website
4. WSDOT Design Manual Chapter 1320 Roundabouts
Additional research sources on roundabouts
A Policy on Geometric Design of Highways and Streets (Green Book), AASHTO, 2004
“Crash Reductions Following Installation of Roundabouts in the United States,”
Insurance Institute for Highway Safety, March 2000
Guide to Traffic Engineering Practice, Part 6 – Roundabouts (Austroad Guide),
Highway Capacity Manual (HCM), Special Report 209, Transportation Research
Board, National Research Council
Modern Roundabout Practice in the United States, NCHRPSynthesis 264,
Transportation Research Board, 1998
Roundabouts: An Informational Guide, FHWA-RD-00-067, USDOT, FHWA
Roundabout Design Guidelines, Ourston & Doctors, Santa Barbara, California, 1995
The Traffic Capacity of Roundabouts, TRRLLaboratory Report 942, Kimber,
R.M., Crowthorne, England: Transport and Road Research Laboratory, 1980
“Use of Roundabouts,” ITE Technical Council Committee 5B-17, Feb. 1992
The Design of Roundabouts: State of the Art Review, Brown, Mike, Transportation
Research Laboratory, Department of Transport. London, HMSO, 1995
Understanding Flexibility in Transportation Design – Washington, WSDOT, 2005