An intergovernmental workgroup has completed its work and released its report about the Montlake Bridge and the 520 project’s impact on flows across it, written by Nelson/Nygaard. The results hit the street today and will be considered by the Council on Monday. Here’s the one page summary (.doc). The full report is here.
WSDOT included a second bascule bridge in its preferred alternative, which would add two HOV lanes to the current four general purpose lanes and widen each. The city pushed back, reflecting neighborhood opposition to a wider roadway. So a new workgroup developed “triggers” for new bascule bridge construction.
The study looked at bike/ped, transit, and “mainline” impacts. By “mainline”, they mean traffic flow on the 520 bridge. It’s bad news for anyone who wanted to see a new bridge. The conclusions were:
- Bike/Ped: Current bike and pedestrian capacity is inadequate, probably already exceeding reasonable triggers, and the City should explore options for improving it without building a second bridge.*
- Transit in the corridor is at or approaching the threshold that defines failed service delivery due to unreliability and low speed, and is likely to be well over the line soon. If service quality degrades from 2011 levels, the state should consider building the bridge. However, there is “no evidence” that the bridge “plays any substantial role” in the delays, and other corridor improvements are more cost-effective than a new bridge.
- Mainline traffic is only affected by the bridge when it opens. A second bridge might clear this disruption faster, but that’s a marginal improvement.
I have no trouble believing that an equivalent value of 23rd Ave corridor improvements in the Transit Master Plan would yield better performance gains for the 43 and 48 than a second bridge. The bascule bridge has little impact because in any case buses have to merge with general purpose traffic to get into the left turn lane to Pacific. So extending the HOV lane across the bridge just moves the merge point north a few feet — a minor improvement at best.
That’s unfortunate because of how much depends on bus efficiency here. With a new Link station and no Montlake Flyer Stop, the entire transit system would be more efficient with a seamless flow from the interchange to the Link Station. Metro and Sound Transit could get mostly out of the business of sending buses downtown via 520. The transfer to Link is already damaged by a long walk from the bus stop that crosses at least one street at grade. More than ever, every minute counts. Improvements at random spots on 23rd might be great for the 48, but will do nothing to help the 542 or 271.
However, there are two other potential problems with the conclusion that HOV lanes on the bridge aren’t that important.
First, in a world where common sense ruled, the State would clearly have the same obligation to pay for mitigation whether it took the form of a new road bridge or transit priority treatments. However, after a few trips to the mega-project rodeo, we know how this goes. The Montlake bridge is a car bridge on a state route, so it’s in WSDOT’s wheelhouse. Transit priority treatments on 23rd? One can picture the relief in Olympia: “That’s a city responsibility.” Rather than trading the new bridge for something more cost-effective, Seattle might trade it for nothing. It will take vigilance by Seattle leaders to prevent this from happening.
Second, the second bridge will be far from shovel ready. If the trigger conditions are met and policymakers desire a more general reform of this corridor, that is merely the beginning of a process to study the utility of another bridge. After that grinding experience, someone will have to come out with money to build it. Meanwhile, transit riders will spend years suffering an inadequately engineered route.**
* Perhaps by retrofitting the current bridge or building a much cheaper bike/ped bridge.
** Metro GM Kevin Desmond’s comments, appended to the end of the report, are notable for being the only ones that seem to really be worried about the bus.