To someday build a Ballard-to-downtown light-rail line, taxpayers could spend less than $500 million for tracks on the surface, passing west of Lake Union.

Or for a cool $2.5 billion to $3 billion, drill tunnels under Queen Anne Hill and the Lake Washington Ship Canal.

Or any of several options in between.

Sound Transit and the Seattle Department of Transportation are examining those routes for a potential “Sound Transit 3” ballot measure in 2016.

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An open house is planned Thursday night in Ballard, followed by another round of outreach this winter and a final report by spring.

Six of the eight options call for running trains entirely in their own right of way — elevated or tunneled along some stretches, or at street level, like the Link line’s Rainier Valley segment.

But two options include sharing road lanes with general traffic, either the whole way or just on the existing South Lake Union streetcar tracks. Officials are also considering whether to give exclusive lanes to the South Lake Union streetcar, which is already delayed by car traffic.

Transportation staff and elected officials may well decide to “mix and match” features, said Karen Waterman, a Sound Transit project planner, who led a briefing Wednesday.

Some highlights:

• A station at the top of Queen Anne Hill, like the existing Beacon Hill Station, appears in some versions.

• A new transit bridge over the Ship Canal might be a 140-foot-high span or a 70-foot drawbridge that occasionally opens for boats.

• Seattle would build separated bike lanes known as “cycle tracks” downtown, even if light-rail tracks are also being contemplated. Diagrams show both train and cycle track on Second Avenue, for instance, after removal of one general lane and on-street parking.

• Trackways could force lane reductions on Second and Fourth avenues, now used by suburban buses. Officials say that when Link reaches Northgate in 2021 and Lynnwood in 2023, North End commuter buses would shuttle riders to and from those outlying stations, instead of going downtown.

A Ballard line wouldn’t happen without a new tax source. Sales-tax revenues are maxed out building light rail to Overlake, Lynnwood and Highline Community College by the early 2020s. So the Legislature would have to let Sound Transit seek some new funding source. In that case, a Ballard line would stand on the ballot alongside other regional proposals, such as lines to Everett, Redmond and Federal Way.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com. On Twitter @mikelindblom