Final Alternatives Report
All alternatives presented in this document all involve the reconstruction of the SR-520
bridge, which is reaching the end of its design life.
Alternative 1: Reduce number of onramps.
The reconstruction of SR-520 with a fewer number of onramps will result in a number of
pros and cons.
Some major benefits are:




Freeway traffic will flow faster due to less slowdown caused by merging cars.
Accidents caused by merging vehicles will be reduced.
Total number of freeway trips will be reduced, causing fewer vehicles to use the
freeway if it is made less accessible.
Cheaper reconstruction of SR-520, since there are fewer things to build
Some major disadvantages of this plan are:


The traffic load on remaining onramps may increase, resulting in more congested
local streets.
The plan favors those living farther away, because they rely on the freeway more
and locals near the freeway will have a more difficult time accessing the freeway.
Alternative 2: Put bus and HOV in the inside lane
Moving the side of the HOV lane is expected to help with three current problems:



First, the buses and HOVs which are supposed to be going fast are slowed down
to accommodate merging traffic from on-ramps and to off-ramps.
Second, it could cause congestion at ramps where general purpose (GP) traffic
has to weave across the HOV lane to enter and exit the freeway.
Third, it is a safety hazard if speedy buses and HOV have to brake often for
people who are trying to get on and off the freeway.
So moving HOV to the inside lane would be able to allow buses and HOVs to travel
faster, reduce the congestions at ramps and increase the road safety. But this is not easy
to implement because:


Buses have to pull off and back on to the HOV lane at two stops on westbound
SR-520 between I-405 and Evergreen Point station.
Another barrier for this alternative is the current HOV lane condition. The lane
was created in the 1970’s out of a shoulder. It’s narrow, has no shoulder and
winds through merging traffic from on and off ramps. It thus can’t safely carry a
high volume of traffic the way regular lanes do.
Alternative 3: Increase Transit Use
Improving the transit system such as building a big Park and Ride (P&R) with other
facility and more frequent arrival/departure time at this P&R will have several benefits:






Having more frequent arrival departure bus time and place to hang out will give
people more incentive to use public transit
Land use intensity is increased by having a P&R with other facility such as coffee
shops, grocery stores, etc.
Other facilities/businesses at P&R will increase economic benefit for the
community around P&R
People who use public transit will be forced to exercise since they will have to
walk from bus stop to bus stop.
As more people ride buses, there will be fewer vehicles on the road. This will
reduce congestion and air pollution caused by vehicles.
More bus and fewer vehicles mean that natural resource will be shift to diesel
fuel from gasoline fuel.
This option has few problems that must be solved before and during the implementation:




It would be difficult to find a sufficnetly large space for a new P&R
It would be hard to predict how peoples’ behavior would change by providing this
new P&R
Pavement life is mostly affected by how much heavy vehicle travel occurs across
the pavement. Small vehicles such as sedans and SUVs have minimal effect on
pavement. On the other hand, buses are heavy enough to have significant effect
on pavement. Increasing the amount of buses traveling across SR-520 could
significantly decrease the pavement life of SR-520.
If people are more willing to ride a bus than drive a car, there would be a decrease
in the number of jobs in the auto sector.
Alternative 4: Ski Gondola
The addition of a cabled gondola ride across the SR-520 Bridge would have the following
positive effects:





It would reduce the number of busses needed to cross the bridge by providing an
alternate mode of travel. By reducing the bus traffic the overall congestion across
the bridge will lessen.
The gondolas are environmentally friendly because they do not produce any
emissions. They will run off electricity.
They will continuously run so there is no wait time.
The gondolas are completely enclosed to protect riders from the elements.
It would become a tourist attraction. Each gondola will have a 360 degree view
of lake Washington.
The negative aspects of this alternative include:





The riders’ perception of safety would be low due to suspension from the cable
and a mechanism detaching and reattaching from the cable during the loading and
alighting processes
There could be a safety risk for the riders while boarding the gondola.
The gondolas have the same problem as buses, in that the riders’ belongings are
limited to what they are able to carry.
The gondola would have a limited service area. If continuing on into downtown
Seattle riders would have to catch a bus once they crossed the bridge in the
gondola.
This alternative would not reduce the number of SOVs on the bridge. Instead it
would compete with other mass transport options.
Alternative 5: conveyor belt
The addition of a large conveyor belt on the side of the SR-520 would result in the
following benefits.




The conveyor belt would be constantly running and would be able to move many
people at once.
It would be covered in glass so it would protect the pedestrians from the elements
as well as provide a nice view of Lake Washington.
A separate bike lane would also have a conveyor belt to speed up bike travel.
Chairs would be placed on the conveyor belt so the riders would have the option
of sitting down.
The following is a list of the negatives of this alternative:





Safety is a large concern. Many people will have problems getting on the
conveyor belt, the may lose their footing and fall. Another safety concern is long
hair and loose clothing getting caught under the conveyor belt.
Reliability of the system is in question.
The conveyor belt would have a limited service area. If continuing on into
downtown Seattle riders would have to catch a bus after crossing the bridge.
Requiring the users to pay would be difficult since similar people movers are
offered for free in airports.
The amount of personal belongings each rider could have would be limited to
what he/she could carry in their arms.
Alternative 6: Magnetic Gizmo
Replacing a traditional bridge with a large cable system that transports cars via magnet
from one side of Lake Washington to the other has only the benefit of not having a
bridge. This alternative has many faults. The following is a list of negatives of this
alternative:









Safety is a huge concern with this alternative. If a magnet failed to pick up a
vehicle, the vehicle would have no place to go but into the lake. Also if there was
a problem with the magnet in the air the vehicle could drop into the lake. Serious
health risks to passengers with pacemakers caused by the electro-magnetic field.
This alternative is costly and would require extensive engineering.
By having only one cable of magnets, this alternative becomes slower than a
traditional bridge with multiple lanes.
If there were a power outage the system would shut down and the vehicles would
all drop into the lake.
The perception of safety is very poor. The vehicle would be dangling in the air.
Having a system like this that would fit for every type of vehicle is impossible.
Trucks would have to be picked up differently than cars or motorcycles.
If there were a backup on one side of the water, there would be a massive system
failure. The magnets would keep dropping off vehicles whether there is room for
them or not.
Since there is no way of collecting oil that drips from the vehicles, this alternative
is not environmentally friendly.
This system has a small capacity and would meet this capacity after a short time
of operation. This system has no way to handle an overload of capacity.
Alternative 7: Multimodal High-Tech Solution
This alternative, while providing a generally flexible and multimodal combination of
solutions to some of the SR-520 problems, has problems of its own. Some of the benefits
include:
 This alternative has a user-based fee structure. Users who cause the greatest
burden on the system pay the highest fees, while those using modes with lower
congestion impacts pay lower fees. This is especially important for political
reasons (e.g., eastern Washington residents will not claim they are subsidizing the
project).
 Recent advancements in RFID technology, fast computers and networks, and
relational databases will allow the system to work efficiently. Incentive for
compliance by drivers is enhanced by a low per-incident cost for non-compliance,
but a high total cost for non-compliance (refusal of the state to register vehicles
for non-compliant drivers who do not pay fines).
 This alternative plans for multiple modes of travel: rail, bus, bicycle, and car.
Substituting much of the current auto volume for lower-congestion and more
environmentally friendly modes increases quality of life for residents. Rail will
increase the speed and reliability for non-auto travelers. Adding the third lane
anticipates the continual long-term increase in auto traffic, even considering
substitution of other modes.
There are several major flaws with this alternative.



The proposed changes will be costly. The development of an integrated
RFID/toll/photo/database system would be complicated and expensive.
Our client recently informed us this alternative raises issues of legality.
Adding an additional lane will also be costly (although all of our alternatives
include rebuilding the bridge, adding an additional lane at the time of construction
is lower than the cost of retrofitting).
Alternative 8: Pedestrian/Bike Lane
Adding an extra lane solely for pedestrians and bicycles will have several benefits:



It would provide nice bridge for people to exercise on.
It would provide a nice recreational area.
It satisfies the latent demand for walking and biking.
But this would have several problems:


Pedestrian/bike lanes require dedicated space
These extra lanes will not have a substantial impact on congestion reduction in
SR-520
Alternative 9: Light Rail
A light rail line along SR-520 will provide an alternative to congested freeways as well as
the following advantages.




Trains are more safe and reliable than buses because trains run on independent
rails and thus would not be affected by the ground traffic.
Trains can carry more people than buses to their jobs, homes, shopping and other
activities every day.
From the environmental perspective, trains being operated by electricity do not
generate emissions as other gas dependant vehicles do. In a long run, rail will
minimize vehicle caused pollution and thus lead to better air quality.
The addition of a light rail line along SR-520 is expected to cross paths with the
upcoming Sound Transit Link Light Rail line from Sea-Tac airport to Seattle.
This will provide more convenience to the eastside residents.
However, there are also disadvantages to building a light rail line along SR-520:





Light rail requires dedicated infrastructure no matter if it is going to use a shared
or exclusive right-of-way. As a result, a large quantity of money will be needed
for the possible road expansion, elevation or underground construction.
Preparing SR-520 for light rail will pose some construction inconveniences.
Temporary lane closing would cause the currently congested traffic to be even
worse. In addition, some relocation or noise would be unavoidable in the affected
neighborhoods.
Light rail is more prone to system failure because all the trains run on the same
rail, so a failure of one train would block all the other trains. In contrast, buses are
independent one another.
The ridership would not be known until it opens. This uncertainty is a major
problem for the forecasting typically desired in decision making.
The possible noise and shake caused by light rail is also a concern to SR-520
users and local residents.
Final alternative ranking:
The final ranking of the alternatives is based upon the INSTEP team views as to the
reasonability of a project and the likelihood of project acceptance.
Based on this, INSTEP ranks the alternatives in the following order:
1. Alternative 3: Increase Transit Use
This is the easiest alternative to implement since people would not have to
move in order to increase transit ridership. We would only need to build more
park and rides facilities (or parking garages) from which we could increase the
number of buses arriving and departing from each garage. Communities
would be more accepting of such an idea because of the increased income
brought to the area.
2. Alternative 7: Multi-Modal Solution
This plan will provide a considerable amount of benefits; however
implementation is the major disadvantage of this plan. The public resistance
to toll booths is likely to be very high. Also, issues of the legality regarding
photographic/radio tracking of vehicles will make this plan less desirable to
decision makers.
3. Alternative 1: Reduce Number of Onramps
This alternative will be fairly easy to technically implement, since it will
primarily involve closing a few onramps onto SR-520. However, local
communities could raise sufficient opposition to kill this alternative.