If you built it, they will come. Or will they?

With the Expo Line’s extension from Culver City to Santa Monica set to open May 20, it remains to be seen how many people will use the new trains in a region known for its clogged freeways and traffic-jammed commutes.

Metro officials project that the light-rail route from Downtown Los Angeles to Santa Monica will have 64,000 daily riders by 2030 as residents, workers and visitors adjust to the expanded east-west transit option.

Ridership numbers are expected to climb on the Expo Line specifically because of the addition of the 6.6-mile, $1.5-billion extension project, which features seven new stations and which brings track-based transportation to the Westside for the first time in decades.

“With the Expo Line Phase 2 to Santa Monica,” Metro CEO Phil Washington said recently, “we have a great example of how Metro is expanding and organizing our transportation network to better serve our region and help ease traffic.”

Metro officials hope the new transit line provides long-term relief even as the agency faces sagging ridership across the system. The existing Expo Line recorded 783,581 boardings last month, a 3-percent drop from April 2014.

There were 29,047 average weekday boardings on the Expo Line last month, a roughly 3-percent decline from the 29,917 a year earlier. The agency recorded 21,945 average Saturday boardings last month, a 7.5-percent decrease in ridership from two years earlier. Sunday and holiday ridership has also slipped slightly, dropping from an average of 16,254 in April 2015 to 15,965 last month.

“Our ridership declines are in line with the nation as a whole,” Washington said in his State of the Agency report earlier this year. “Transformation through transportation takes time and patience. As the county grows over the next 10 years, now is the time to plan for future growth and now is the time to position ourselves to invest in transportation needs for decades to come.”

Rail commutes currently make up a small percentage of Metro ridership, according to agency data. Of the 35 million rides logged by the agency last month, 8.8 million came on rail lines and the remaining 26.2 million were tallied on buses.

But ridership on the existing Expo Line trains from Downtown Los Angeles to Culver City is “exceeding expectations,” officials have said.

Metro is trying to usher people onto the new rail line by offering free rides from noon to closing on opening day and all day May 21. The one-way fare will be $1.75 thereafter.

Weekday service will begin at about 4 a.m. and continue until midnight, agency spokesman Jose Ubaldo said. Trains on Friday and Saturday nights are expected to run until about 2 a.m.

Trains will run every 10 to 15 minutes at most times of the day, officials said.

“We encourage the community to enjoy this new light-rail line service and see for themselves how close to the beach Metro can get you,” Washington said.