Montgomery County Executive Isiah Leggett said Thursday that building a countywide system of express bus lanes could take 20 to 30 years, rejecting a recommendation by a county task force to build it in nine years.

“We’re talking about something that at its best-case scenario will take 20 to 30 years,” Leggett said at a public hearing in Rockville. ”This is a long, long process.”

Leggett was responding to dozens of residents, civic activists and smart-growth activists who testified at the hearing. In May, Leggett’s task force released a report that called for a 160-mile, 25-route network aimed at easing traffic in one of the region’s most congested areas. The system is estimated to cost about $1.8 billion to build and $180 million a year to maintain.

In the report, the task force recommended that the county create the system in nine years. The group also considered another option — a 20-year plan — but Leggett’s comment suggests that not even that option is practical.

Those who testified provided a wide array of opinions on the system. Some appreciated the potential improvements to mass transit, some thought the system is too expensive and some wanted a trial period with only a few bus lanes.

Thomas J. Street, an assistant chief administrative officer who has been working extensively on the system, said executive staff members are assessing the task force report and will soon be offering recommendations to Leggett on a suitable plan.

Street said he believes Leggett will offer his suggested plan to the County Council by September. Leggett said at the hearing that he does not expect his recommendation will “satisfy everyone.”

The County Council will be tasked to figure out a way to fund the system. The task force has recommended the creation of special tax districts, but several civic activists testified at the public hearing that they strongly opposed taxing residents living near the bus system.

The public hearing was the first time the public could voice their opinions on the task force report to Leggett. According to county documents, a public hearing was supposed to be scheduled before the report was released, so the input could be incorporated into the final version.

Street said more public hearings will be scheduled in the future.

“This is not a closed book,” Leggett said at the hearing. “This is not a decision you make tomorrow.”