Lots of Boise streets have bike lanes. Some have "sharrows": markings indicating that cyclists are likely on the road.

But never before have the city and the Ada County Highway District, which builds and maintains all of Boise's streets, designed an in-town bicycle route that's as long as the Shamrock.

Pavement markings and signs would designate shared travel lanes for bicycles and vehicles along Shamrock Avenue between Executive Drive and the neighborhoods north of McMillan Road.

Signs would indicate to cyclists where the bikeway goes, and also might display distances to destinations in the area and mark approximately how long it will take to get there.

Signals would make it easier and safer for cyclists to cross at three major intersections along the route: Fairview Avenue, Ustick Road and McMillan Road.

The idea for the bike corridor evolved from a 2008 meeting at which residents said they worried about the safety of walking along Shamrock, City Councilwoman Elaine Clegg said. Its design fits with the city's desire to build a transportation system around cyclists and pedestrians, instead of making them a secondary consideration to drivers, she said.

"This begins to piece together the system that serves all users," Clegg said. " ... Not just accommodates them, but actually serves them."

The highway district has proposed two alternative bike routes. The difference between them comes down to how many turns a person would make.

The first option calls for a westward jog to Bryson Avenue between Gunsmoke and Montana streets, which Shamrock doesn't connect.

The second option would extend 10-foot pathways connecting Gunsmoke to Montana, at a slightly greater cost - $591,000 instead of $558,000.

About $400,000 of the cost for either option is for the three signal crossings.

So far, nearly half of the comments the highway district has received prefer the second option. The most common reason? It's a more direct route.

But more than one-third of the commenters say that they're in favor of a third option: not building the bikeway. Cost is one of the most common reasons for opposition.

For some people who live on or near Shamrock, the second option sounds a little too much like a 2009 proposal to extend Shamrock through the undeveloped land between Montana Street and Ustick.

"I think this is just a ploy to bust Shamrock through," said Fisk Smith, who lives on Shamrock. "We have kids. I have grandkids that are outside all the time, and yet we have cars racing up and down the street all the time. And if they make that a throughway, it's even going to be worse."

In February 2010, highway district commissioners voted to leave Shamrock the way it was, for the time being. Highway district spokesman Craig Quintana said the district has no plans to reverse that position.

Sven Berg: 377-6275