In this week's In the Hall, I'll be writing about the prospects for Frank Chopp's vision for replacing the Alaskan Way Viaduct. Although you'll have to wait with bated breath for that one, here's a bit of intel about last week's mobility study that I couldn't quite fit into the column:
Last week, state, city, and county transportation officials released a "mobility study" revealing how travel times would compare between the eight remaining options for replacing the Alaskan Way Viaduct. Proponents of the âsurface/transitâ option were encouraged by the results, which showed that all the options, including two surface options, kept people moving through the city. An elevated viaduct produced the fastest travel times, followed by a tunnel and the surface alternatives.
Critics have pointed, however, to one major flaw in the modelingâa flaw that could lead planners to drastically overestimate downtown traffic levels in the future. In estimating how each option would effect travel times, transportation officials assumed that car trips will keep going up, up, upâby 20 percent in the next seven years. Thatâs in direct contradiction to the stateâs stated commitment of reducing car tripsâknown as âvehicle miles traveledââby 50 percent in the next 40 years. And it reflects a fundamentally flawed view of how people make their travel decisions.
Say you need to drive to the grocery store. If itâs rush hour, and you have some flexibility, youâre may decide to make your trip at another time, combine it with other errands later in the day, shop online, or take a different route. Thatâs because youâre human, and humans adjust their behavior to fit changing circumstances. The stateâs viaduct planning model, however, assumes they never do that. Ron Paananen, the stateâs viaduct project director, says state planners will âstart talking about changes in demandâ when they do projections for 2030âbut had they considered the way people actually behave this time around, their estimates for travel times would probably have been much lower. If hurrying up traffic is no longer the most important consideration, the surface/transit option starts to look even more appealing.