So where does the Viaduct traffic go if we don't build a new highway? It spreads out into a cleaner, more efficient grid; it moves to transit; it gets on a declogged I-5; it takes the ferry. Some of the trips don't happen at all. Freight gets its own prioritized routes. Here are the projects that look most promising, based on the early analysis done for the Central City Access Strategy blended with other regional transportation expertise.
- Fix missing and broken links in the arterial system to take advantage of unused capacity and redistribute traffic to, from, and around downtown:
- North End Distributor: provide more north/south choices to cross Denny Way by distributing trips to Dexter Ave, 6th Ave and other SLU arterials better
- South End Distributor: create more and better connections from Spokane Street to 1st Ave, 4th Ave, I-5
- Make better links to Airport Way, 4th Ave, 6th Ave south of downtown
- Fix Mercer Mess and other bottlenecks that impede flow
- Rebuild 4 lanes on waterfront, better connected to the grid
- Time signals downtown for better flow
- Create one-way couplets throughout downtown
Potential result: An additional 20,000 to 25,000 north and south trips/day
- Improve I-5 so through-traffic gets through faster:
- Reduce number of ramps downtown, which means less weaving
- Reorganize express lanes as permanent 2-way through traffic
- Consider freight-only lanes or allowing freight on HOV lanes
- Consider signage north and south of Seattle to send thru-traffic on I-405
- Charge tolls at peak periods to reduce rush hour demand
Potential result: An additional 15,000 to 20,000 trips/day
- Optimize regional public transit to accommodate trips formerly taken on the Viaduct:
- Create better bus connections to get maximum riders on light rail
- Unify transit system maps, signage, and information-- easier to figure out and use
- Optimize transit reliability so it's competitive with the freedom of driving alone
- Lure new users over to transit during countdown to viaduct closure
- Develop a Mosquito fleet plan to serve former viaduct trips with pedestrian ferries across Elliott Bay to Ballard, Magnolia, and West Seattle
- Consider trolley circulator from South Lake Union to the waterfront, the stadiums, and the International District.
Potential result: An additional 15,000 to 30,000 trips/day
- Keep freight moving, especially between BINMIC and SODO industrial areas:
Other cities have figured out how to prioritize freight mobility using surface roads. If Seattle is serious about freight mobility, then investing in the city's Freight Mobility Strategic Plan to improve freight access throughout the city will likely offer superior economic returns for more users than investing in a single new facility.
- Identify freight only lanes on linked arterials through city
- Consider freight only, or freight + HOV, lanes on I-5
- Consider freight priority on targeted arterials during specific hours
- Create better freight signage and real time information throughout city
- Consider better freight connections for Port/SODO to I-90
- Reduce demand for highway-driving with denser, more walkable neighborhoods, incentives for non-car travel (better transit coordination, pedestrian and bike facilities) and aggressive trip reduction measures (peak-hour tolls, parking taxes, etc.):
Maintaining 100% of capacity in this corridor may not be a necessary, nor affordable, goal, given the high costs of building a new highway. Other cities have shown that population and the economy can keep growing and thriving, with less highway capacity than Seattle. People are more flexible that transportation planning models give them credit for. The number of daily trips on the Viaduct isn't fixed, and it isn't permanent. Consider these facts:
- The day before the earthquake in 2001, 110,000 vehicles used the Viaduct. In the months after it reopened, usage declined to 80,000 vehicles/day. Some of the missing 30,000 trips weren't made; some took another route.
- On average, people move either their employment or their home once every three years, which entirely changes their commuting pattern. Given 5 years warning that the viaduct is going away, many of us can adjust accordingly.
- A study in Great Britain found that when a highway is closed, an average of 25% and up to 60% of the trips that had used the facility just disappeared.
- WSDOT studied the effect of charging a $1 toll on the new facility, to see if tolls might be part of the funding solution. They found that roughly 40,000 trips / day would not use the facility. How important was that trip if it wasn't worth $1?
- Waterfront freeways removed in Portland (by law) and in San Francisco (by earthquake) created no additional gridlock or adverse economic effect, as opponents of the removal of these highways had predicted.
- A UC Berkeley study of four urban California counties from 1973 to 1990 found that for every 1% of added road capacity, traffic volume increased by 0.9%. This phenomenon is known as induced demand: if you build the roads, people will drive them. The reverse is apparently true as well.
Therefore, a rough estimate based on the above examples and Seattle's own post-earthquake experience suggests:
Potential result: A reduced target of up to 30,000 trips/day
The measures listed above expand our downtown vehicle and transit capacity by a rough estimate of 50,000 to 75,000 trips per day. These fixes help all travelers in Seattle - not just those on the waterfront. It estimates reducing demand for trips by 30,000 trips/ day; all the important trips can be accommodated, including crucial freight trips, and trips that don't have to be made by car aren't, because there are other options. Offering a range of convenient choices and incentives to shift travel patterns away from car use is consistent with the vision of every planning document the city and region have produced in the last twenty years.
But how does growth get accommodated? There will still be more untapped capacity on the Bus and Light Rail systems. And with good planning, vehicle trips don't have to expand with population growth. In Vancouver, B.C. the downtown population increased by 50% from 1991 to 2001 while the number of miles driven FELL in the same period. Studies of successful Transit Oriented Development have revealed that while the average proportion of people who choose to live car-free is 5%, the rate jumps to 16% for those who live within ½ mile of a transit station.
And finally, researchers at the Surface Transportation Policy Project found that "road building (capacity expansion) seemed to have little impact on congestion. Between 1982 and 1997, metro areas that were aggressive in expanding the amount of road space per person fared no better in terms of rush hour congestion than those that did the least to add new road space; in fact, they did slightly worse. "
Smart transportation experts challenge the economics of any further investment in urban highways. By the time a new highway started today is finished, baby boomers will be retiring, walkable lifestyles will be much more valued, and gas prices will be significantly higher. Many market and demographic trends point toward a future society that drives less. A new report from the Victoria Transport Policy Institute concludes "It may be better to anticipate these trends by investing in alternative modes and creating less automobile-dependent communities."
Once a neighborhood is dense enough, services locate there and people walk, bike, and use transit instead of driving. So as Seattle grows denser, neighborhoods will get more self-sufficient and walkable, and more people will get comfortable using more reliable and convenient transit.
And if we did replace the Viaduct, and decided to close it during construction to control costs, don't you think people would have figured out a different way to get where they're going during the five to eight years it would take to rebuild?