DH writes: "and the streetcar line came in $6 million under budget".

This is not so. SDOT will spend the rest of the calendar year estimating the cost and doing environmental analysis of the alignment that the Mayor and Council have selected. SDOT has only done the preliminary cost estimate. It's early yet.

The fall in ST2 sales tax revenue seems irrelevant to the expenditure of funds already allocated to the First Hill Connector streetcar.

Seattle would have to fund the extension, not just a study of the extension. The capital cost of the extension not only includes the trackway and overhead, but also anotther streetcar to maintain the headway over a longer alignment. An LID could be used for part of the capital cost of an extension. If Seattle had more funds to spend on the streetcar, and they do not, improving service frequency over the Denny to Pioneer Square alignment would be more effective than an extension. The ST2 plan has 15-minute headway in the off-peak.

Back to the cost estimation. SDOT may discover higher costs than expected to place the streetcar tracks on the viaduct over the BNSFRR mainline; they may discover higher costs than expected to integrate with the electric trolleybus network; they may find traffic impacts of adding streetcar platforms in busy arterials and intersections.