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SR 520 Bridge Program: Medina to SR 202 Eastside Project Map

Ultimate project features

Eastside project map ultimate features
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Eastside HOV lane configuration - with summer 2014 expansion

Eastside project map current features
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New inside HOV lanes between Lake Washington and 108th Avenue Northeast opened in September 2014. The lanes align with new median transit stops and direct-access ramps for carpools and buses. Read the Q&A below to learn more.

Q&A: SR 520 HOV lanes on the Eastside


How did the Eastside Transit and HOV Project change the lane configurations on the Eastside?
The project created inside HOV lanes between the SR 520 floating bridge and 108th Avenue Northeast. The new lanes align with two new median transit stops (at Evergreen Point Road and 92nd Avenue Northeast) and direct-access ramps for carpools and buses (at 108th Avenue Northeast). The new HOV lanes, open since September 2014, improve transit connections and travel times along the rebuilt corridor.

How do the SR 520 HOV lanes operate on the Eastside?
The Eastside SR 520 HOV lanes operate as follows:

  • West of I-405: Buses and carpools travel in the inside lane, with a 3-person minimum occupancy requirement for carpools – the same occupancy requirement as before project construction.
  • East of I-405: Operations remain the same. Buses and carpools travel in the outside lane, with a 2-person minimum occupancy requirement for carpools.

Why are the HOV lanes on the outside east of I-405?
Our ultimate plan is to move the HOV lanes to the inside all the way to SR 202 in Redmond (see the map at the top of this page). As regular users of SR 520, we know there is significant congestion on a daily basis in the vicinity of the SR 520/I-405 interchange. Our analysis, however, found that until substantial changes are made to the interchange, moving the HOV lanes to the inside would actually increase congestion on SR 520.

What causes the congestion at the SR 520 / I-405 interchange?
We see the heaviest congestion during the afternoon commute. Currently, nearly 60 percent of westbound vehicles on SR 520 exit onto I-405. This creates long backups in the right-side through lane as cars line up there to exit onto I-405.

Wouldn’t an inside HOV lane east of I-405 help the situation?
Unfortunately it wouldn’t, not without other changes to SR 520 and the interchange with I-405. There are simply too many cars and not enough highway capacity for traffic to flow smoothly. Westbound SR 520 is three lanes wide where it crosses under I-405. The right lane is often congested with vehicles exiting to southbound I-405, especially during the afternoon commute. That leaves just two lanes for vehicles continuing west toward Seattle. If the inside (left) lane were changed to an HOV lane, non-HOV drivers effectively would have only one through lane when the right lane is clogged with vehicles waiting to exit.

What about buses and carpools, wouldn’t they be better off with an inside HOV lane east of I-405?
Without first making improvements at the SR 520/I-405 interchange, an inside HOV lane would force all non-HOV vehicles into one westbound general-purpose lane when traffic is heavy – and that could significantly worsen congestion at the interchange. Putting the HOV lane on the inside at this time might improve bus and carpool travel for some HOV users, but WSDOT has to balance the needs and traffic flow of all road users.

What is WSDOT’s plan to ease congestion at the SR 520 / I-405 interchange?
We have developed plans for three construction projects to reduce congestion and improve traffic flow at the interchange. They are explained more thoroughly in this WSDOT fact sheet (pdf 1.4 mb).

1. New ramps at the 124th Avenue Northeast interchange
Building a westbound off-ramp and eastbound on-ramp at 124th Avenue Northeast will create a full diamond interchange to the east of I-405. Since Bellevue is the destination for most of the westbound SR 520 vehicles that exit onto I-405, this project will give motorists an alternate route into Bellevue and reduce traffic volume and congestion at the SR 520 / I-405 interchange.

2. Direct-access ramp from westbound SR 520 to I-405
Creating an inside-lane direct-access ramp onto I-405 express-toll lanes for buses and carpools leaving westbound SR 520 will further reduce congestion at the often-congested interchange and improve transit and HOV travel times. This new ramp also will improve travel times for non-HOV users because vehicles in the westbound HOV lane no longer will need to merge right and take up space in the regular exit ramp to I-405.

3. New SR 520 auxiliary lanes
Building SR 520 auxiliary lanes between 124th and 148th avenues will essentially create a fourth lane east of the I-405 interchange. This added westbound lane for cars entering or exiting SR 520 will free up capacity and ease congestion in the existing through lanes for vehicles proceeding west toward Seattle.

When will these projects start?
The timetable depends largely on state funding. There are many pressing transportation needs across the region, and the dollars currently are not available to upgrade the SR 520 / I-405 interchange. We are working with the state Legislature to identify funding for these and other high-priority projects. In the meantime, until these improvements can be made, WSDOT, King County Metro, Sound Transit, and local jurisdictions on the Eastside agree that the current HOV alignment on the Eastside, while not ideal, is preferable to an all-inside HOV alignment.

Is WSDOT planning other changes to the HOV system?
Yes, we’re actively studying ways to improve our highway system for all users – transit riders, carpoolers and solo drivers alike. Like much of our transportation system, the Puget Sound region’s HOV lanes are stressed. WSDOT, in collaboration with local transit agencies and jurisdictions, is evaluating a variety of ways to get more out of our HOV network. There is no easy or quick fix, but some of the options we’re exploring – and in some instances implementing – include more express-toll lanes and an HOV 3+ requirement for toll-free access to express-toll lanes.