NE 51st Street Improvements
Location: NE 51st Street between Westbound 520 On-/Off-Ramps and 156th Ave NE

Project Phase: Design

Estimated Timeline: Construction start is anticipated in late 2018 or early 2019

Project Manager: Eric Dawson, 425-556-2867

Page Last Updated: 10/04/18

Project Overview:  The City of Redmond is designing a transportation project on NE 51st Street with the following main components:

  • Improve signal efficiency at the intersection of 51st Street and 156th Avenue by constructing a new eastbound left turn lane and converting one of the two westbound approach lanes to a dedicated left turn lane
  • Add a new two-way left-turn lane on 51st Street to serve 154th Avenue
  • Install bicycle lanes between the Eastbound SR 520 ramps and 156th Avenue
  • Adjust curves and install truck aprons at the intersection of 51st Street with the Westbound SR 520 ramps

NE 51st Street Project Location Map


Project History:

City Plans

NE 51st Street is designated as a minor arterial street with plans for roadway improvements including bicycle lanes and turn lanes in Redmond’s Transportation Master Plan.

Microsoft Development

Microsoft proposed the construction of two new buildings south of NE 51st Street approximately ten years ago. New buildings are required to undergo a transportation review. This review required several transportation projects to be completed as mitigation for the new buildings:  

  • Intersection improvements at 156th Avenue at 45th Street
  • Turn lanes at the intersection of 51st street and 154th Avenue
  • A bicycle lane on the south side of 51st Street from the eastbound 520 off ramp to 154th Avenue 

In 2016 Microsoft agreed to fund the NE 51st Street improvements paid for by Microsoft through a financial mechanism called a “community facility district”. Redmond City Council approved the petition for a community facility district with the condition that Microsoft also fund the completion of bicycle lane on the north side of 51st Street from 154th Avenue to the eastbound 520 on-ramp, as called for in the Transportation Master Plan.

Redmond initiated design of the 51st Street Improvements in late 2016. To date, the City has updated the 2008 Microsoft transportation study, advanced design to 60%, and held a public meeting in March 2017 to review the project.

Connecting Washington

The Washington State Connecting Washington transportation revenue package is providing funding to improve pedestrian safety at the intersection of 51st Street and the Westbound SR 520 ramps. This includes installation of truck aprons intended to slow down turning movements.

Public Input

Redmond held a public meeting in March 2017 to discuss the 51st project. The project team heard significant interest in the project from the community around three main themes: 1) Support for the addition of an eastbound left turn lane at 156th Avenue, 2) Concern about ingress/egress at 51st Street and 154th Avenue, and 3) Traffic issues on 156th Avenue north of 51st Street.

Redmond’s design team has been reviewing these interests and coordinating with the Washington State Department of Transportation and Sound Transit regarding these improvements. Here is the current status of each item:

  1. Support for the addition of an eastbound left-turn lane at the intersection of 51st Street and 156th Avenue.
    Resolution: This scope of work has been added to the project. Microsoft, the project sponsor, supported this addition and Redmond City Council subsequently authorized the additional expenditures to complete the work.
  2. Concern about ingress/egress at 51st Street and 154th Avenue.
    Resolution: The consultant engineer team generated a signal warrant analysis at this intersection. Redmond’s City Traffic Engineer reviewed the report and applicable Federal information and made a determination as described below.
  3. Traffic issues on 156th Avenue north of 51st Street: Sign to I-405 misdirecting drivers north of 51st Street and sight distance for southbound vehicles.
    Resolution: The City has revised signage to provide a larger, clearer arrow pointing left to SR 520 and I-405. In addition, Redmond has worked with the property owner at the northeast corner of 51st Street and 156th Avenue regarding sight distance and will be following up in the future to ensure the sight distance triangle is provided at this location.

51st Street and 154th Avenue Traffic Control Decision Findings


The City has evaluated traffic patterns at the intersection of 51st Street and 154th Avenue and has determined that installation of a traffic signal is not preferable at this time. However, given community interest in a signal, the 51st Improvements project will install spare conduit where trenching is already occurring – a low-cost investment that reduces the cost of a signal if installed in the future.

Traffic Analysis Reports

This decision comes after two traffic analyses of the intersection at 51st Street and 154th Avenue/Place: the 51st Operational Analysis and the 51st & 154th Supplemental Signal Warrant Analysis Assessment. The Operational Analysis concludes that a two-way left-turn lane on NE 51st Street would allow left-turns from the minor street approaches on 154th Ave NE to make a two-step left-turn and use the two-way left-turn lane for refuge, therefore improving the level of service for the minor street [154th] left-turn movements.”

A Supplemental Signal Warrant Analysis Assessment was also conducted to determine if a signal would be an appropriate traffic control device for this intersection at this time. The report evaluated Manual on Uniform Traffic Control Devices (MUTCD) signal warrants 1, 2, 3, and 7 and found that warrants 1, 2, and 7 are not met while warrant 3 is marginally met under one of the two conditions. Meeting one warrant means that it is allowable for a traffic signal to be installed but does not determine that it is required or even that installation of a signal is beneficial. The Supplemental Warrant Analysis concludes “because of the close access spacing and heavy peak hour volumes, the NE 51st Street corridor would likely be impacted by the addition of a traffic signal, particularly as it relates to vehicular delays and queuing.”

Federal Requirements and Guidance

A review of Federal requirements and guidance found the following regarding traffic signal installation:
  • Per the MUTCD “traffic control signals are often considered a panacea for all traffic problems at intersections. This belief has led to traffic control signals being installed at many locations where they are not needed, adversely affecting the safety and efficiency of vehicular, bicycle, and pedestrian traffic.”
  • The Federal Highway Administration published a report titled Signalized Intersections: An Informational Guide in 2013 which states “practitioners should take care when using these warrants [warrants 2 and 3]. Many types of businesses generate these volumes at any given time. In most cases, this would not constitute justification for installing a signal” (Signalized Intersections: An Informational Guide, Federal Highway Administration, July 2013).

The MUTCD goes on to list alternatives to installing a traffic signal including “revising the geometrics at the intersection to channelize vehicular movements and reduce the time required for a vehicle to complete the movement.” As noted above the Operational Analysis found that the proposed two-way left-turn lane will revise the geometrics of the intersection and improve level of service.


The combination of the two engineering reports and review of Federal requirements and guidance indicates that:
  1. the installation of two-way left-turn lanes will improve traffic operations at the intersection of 51st Street and 154th Avenue, and
  2. installation of a signal is allowed but should only be installed after careful consideration and after implementation of alternative treatments. In this case the installation of the two-way left-turn lane is the alternative treatment. 

Following completion of the 51st Street widening project and the installation of a two-way left turn lane, the City will monitor the intersection of 51st and 154th to see if there is any significant increase in side street traffic volumes or collisions that may indicate the need to reconsider the warrants for a traffic signal at this location.

51st Street and 154th Avenue Sight Distance Review

The City has completed a review of the sight distance at the intersection of 51st Street and 154th Avenue. This was completed in two steps:
  1. The consultant engineer completed a review of the sight distance and potential alternatives
  2. Redmond’s Public Works Director reviewed the document above and issued a determination regarding sight distance at this location