Mention the 405 Freeway to commuters and you are bombarded with horror stories of bumper-to-bumper traffic and soul-stealing commutes. Add the interchange with the infamous 101 Freeway, and visions of Carmaggedon — even without the lane closures — appear as real-life nightmares.

Starting Thursday, Metro’s senior director of planning will offer some hope to commuters as well as neighbors of the Westside and the San Fernando Valley whose lungs are subjected to freeway fumes from the idling cars and trucks on the jammed routes. At upcoming meetings, he’ll talk about building a 10-mile train connecting Westwood with Sherman Oaks over the Sepulveda Pass.

The online survey from the Los Angeles Metropolitan Transportation Authority on what’s called the Sepulveda Transit Corridor Project has close to 5,000 respondents, and the number is growing.

“The response has been one of the largest response rates on any Metro survey,” said Cory Zelmer, senior director of Metro’s Countywide Planning and Development.

Who wouldn’t want a quicker, less stressful, less-polluting alternative to driving from Westwood, Brentwood, Bel Air, etc. to the east San Fernando Valley communities of Studio City and Sherman Oaks? It’s a no-brainer, except for the cost, which Metro estimated between $17 billion and $38 billion in a 2012 analysis.

Sepulveda Pass

With the two freeways fighting it out for the No. 1 spot in most congested in California and in the top 5 in the nation, the place where they come together presents the biggest challenge for Metro for adding rail, or anything other than a 12-lane freeway.

With more than 400,000 people traveling the 405 through the Sepulveda Pass every weekday to get to work, school or shopping, adding a non-driving alternative would be the agency’s crowning achievement.

“This is a very high profile transit project,” began Dave Sotero, Metro spokesman. “This is Metro’s answer to Angelenos who have always wanted a transit project here, the 10-mile pass between the 10 and 101 freeways.”

So far, Metro’s Measure M, a half-cent sales tax passed two years ago, has about $9.8 billion set aside for the project. One way to close a funding gap is to add a private business partner, something Metro CEO Phil Washington is considering. Last year, Metro said two proposals had passed initial review stages.

Right now, Metro is conducting a feasibility study that could take at least another year to complete. The purpose is to survey residents, businesses, nonprofits and homeowners about what the best route is, where the stations should be placed and which type of rail system should be built — heavy rail as in the Purple and Red line subways underneath downtown, or light-rail such as the Expo Line or the Gold Line.

“This is just an early alternatives analysis process. We are looking at a wide range of options. But we are looking only at rail,” said Cory Zelmer, senior director of countywide planning and development, who will present the plans for a rail service at three upcoming public meetings on Thursday, Saturday and Tuesday, June 12.

San Fernando Valley people and businesses want the project but they don’t want to see Metro skimp.

“We want to make sure the project is not underbuilt,” said Coby King, spokesman for the Valley Industry Commerce Association. “Because of that we are doubtful about light rail.”

The group doesn’t think light-rail would meet the capacity requirements and would be too slow, he said.

Zelmer said Metro is trying to decide between heavy rail and light-rail. Heavy rail would require tunneling through the Santa Monica Mountains, a bigger expense. Also, Metro is asking people to suggest station locations and connections. For example, the new rail line could connect with the Orange Line Busway at Sepulveda or the Van Nuys Station and the Purple Line subway at Wilshire Boulevard and Westwood, a future station and part of the Purple Line subway extension under construction.

Or. it could connect with the future East San Fernando Valley Transit Corridor project, a 9.2-mile rapid bus line or light-rail line that is planned between Van Nuys and San Fernando.

Phase one

Currently, the first phase between the San Fernando Valley and West L.A. is planned for completion in 2033. The second half of the rail line would extend to Los Angeles International Airport but that would not be completed under current project planning until 2057, Zelmer explained.

Los Angeles Mayor and Metro Board Chairman Eric Garcetti wants to see the project sped up. He’s placed it on a list of 28 projects that ought to be opened by 2028, a short 10 years and in time for the Summer Olympic games. “It could be potentially accelerated through a public-private partnership,” Zelmer said.

One project which the mayor said was a possibility was an elevated monorail concept. A Chinese company, BYD, has built several in China. It has a factory in Lancaster where it builds electric buses.

The public meetings on the Sepulveda Transit Corridor Project are as follows:

• Thursday, 6 p.m. to 8 p.m. Westwood United Methodist Church, 10497 Wilshire Blvd, Los Angeles, CA 90024

• Saturday, 10 a.m. to 12 p.m., Marvin Braude Center, 6262 Van Nuys Blvd, Van Nuys, CA 91401

• Tuesday, June 12, 6 p.m. to 8 p.m., Proud Bird Restaurant, 11022 Aviation Blvd, Los Angeles, CA 90045. This meeting will also be webcast live.

Information presented by Metro at the meetings will be the same.