Gov. Larry Hogan announces plans on Wednesday to improve traffic on Interstate 270. (Katherine Shaver/The Washington Post)

Maryland highway officials will try to reduce time-sucking traffic jams on Interstate 270 — the most congested highway in the state and one of the worst in the Washington suburbs — by creating stretches of new lanes without widening the highway, Gov. Larry Hogan said Wednesday.

The $100 million plan also will add signalized meters to on-ramps to control how quickly traffic can merge onto the highway based on real-time traffic conditions. New overhead signs will give more detailed information about crashes or slowdowns ahead and alert motorists to sudden drops in speed.

Maryland transportation officials say the changes will cut up to 30 minutes off the morning commute. That estimate, which officials say is based on actual traffic data, is likely to raise some eyebrows among the tens of thousands of I-270 motorists who regularly slog through a stop-and-go mess most mornings and evenings.

Even so, highway officials say it’s something the state can afford to do relatively quickly to provide some relief — without having to enlarge the footprint of a highway that is already up to 12 lanes wide. Work is scheduled to begin as early as this winter and be completed in 2019, officials said.

“This is not going to fix all the problems of 270,” Hogan (R) said at a news briefing Wednesday at a new shopping center along the highway near Montrose Road. “But if they say it can shave a half-hour off the morning commute in a relatively short period of time while we work with the feds and come up with a long-term solution with Montgomery County, we’re going to do so.”

I-270 is a major commuting route between the Capital Beltway and suburbs north of Washington, such as Rockville, Gaithersburg and Germantown, and Frederick County. The 35-mile highway also is used by commuters who seek more affordable housing as far away as western Maryland, West Virginia and Pennsylvania and serves as the backbone for Montgomery County’s bio-tech corridor, one of the region’s major job centers.

Montgomery County Executive Isiah Leggett (D) called I-270 “the spine of Montgomery County,” saying it’s vital to spurring the county’s economy and accommodating population growth.

“The I-270 corridor is the economic engine of the county and the state of Maryland,” Leggett said, after thanking Hogan for the improvements.

The plan drew immediate criticism from transit activists, who said the state’s money would be better spent on expanding MARC commuter rail and other transit service in the I-270 corridor.

Ronit Aviva Dancis, president of Action Committee For Transit, said adding more highway capacity only leads to more congestion, noting that I-270 filled up even after being widened in the 1990s.

“We widened it to 12 lanes, and it was supposed to solve congestion, and it didn’t,” Dancis said. “We tried this 1950s asphalt solution, and it failed. It’s time to do something else … I’m frankly horrified that so much money is being wasted on something that might only provide short-term, temporary relief.”

Asked about transit advocates’ remarks, Hogan said “there’s just no plan” or money for more transit in the I-270 corridor, apparently dismissing the state’s long-studied but never fully funded plans to build a rapid bus system, known as the Corridor Cities Transitway, in the area.

“We’re investing more here than anywhere else in the state, but it’s not an unlimited, bottomless pit” of money, Hogan said. “I’d definitely like to have more lanes on 270 and some kind of transit solution, but that’s not going to happen. This is an immediate solution.”

The plan pinpoints 14 of the highway’s worst choke points, mostly around interchanges and near the “spur,” where I-270 meets the Capital Beltway.

Many of the changes are designed to reduce merging, which will help traffic flow more smoothly and prevent crashes that cause more backups. That includes 23 new lane miles, most of which will be built by connecting nearby on- and offramps, such as between Falls Road and Route 28. That will prevent motorists traveling a short distance from having to merge into the mainstream traffic, officials said. In other areas, the highway shoulder will become an HOV lane.

A new lane also will be carved into the northbound median near Route 121 to preserve a third northbound lane to the Comus Road overpass, almost a mile north of where the highway chokes as it narrows from three to two lanes — the site of regular afternoon and evening backups.

State officials say motorists will probably feel the biggest relief in the morning, when southbound I-270 will soon retain a third lane as it merges with the Beltway’s outer loop heading toward the American Legion Bridge. That new lane will be created by re-striping that area, officials said. Southbound I-270 also will be reconfigured to add a new express lane to ease the morning bottleneck between Montrose Road and Democracy Boulevard.

In other areas, entrance and exit ramps will be lengthened to help traffic merge more smoothly and help reduce accidents involving cars weaving onto or off the highway.

Greg Slater, Maryland’s highway administrator, said the plan’s strength lies in combining more asphalt with new technology. The “adaptive” ramp meters, he said, will be the first in the state to have sensors monitoring the amount of highway traffic as well as the how much traffic backs up on on-ramps. If traffic on the on-ramp begins to back up toward the local road’s through lanes, he said, the system will know to “flush” all the ramp traffic by keeping the ramp signal green longer to allow traffic to enter the highway.

Slater said the state doesn’t plan to widen I-270 because doing so would be far more expensive and complicated.

“We wanted to get something out there quickly, something that can help people today,” he said.

The Maryland Department of Transportation solicited ideas from the private sector in June, saying the state would pay $100 million for new high-tech ways to “move the most traffic the farthest and the fastest.” Slater said he believed it was the first contract solicitation in the country to ask the private sector for its best ideas, rather than having companies bid on a contract based on detailed government requirements.