WALNUT CREEK — BART riders’ satisfaction with service has dropped to its lowest level in 16 years because of overcrowded, hot trains and dirty seats and carpets, according to a survey of train riders.

The transit agency said the problems are side effects of record ridership as the recovering economy creates more jobs and more commuters — many of whom can’t find seats on trains or spaces in station parking lots.

“BART is a victim of its own success,” BART spokeswoman Alicia Trost said. “We have more people riding our trains than ever, but the same resources to serve them.”

In a survey of 5,600 passengers released Thursday, overall satisfaction with BART service dropped from 84 percent in 2012 to 74 percent in 2014. That figure tied the low mark of 74 percent, set in 1998. The survey has been conducted every other year since 1996.

The number of “somewhat dissatisfied” customers doubled from 4 to 8 percent. The number of “very dissatisfied” customers doubled from 1 to 2 percent.

In a board workshop Thursday in Walnut Creek, BART managers said the survey showed the greatest discontent was found in riders unable to find empty seats, forcing them to stand shoulder to shoulder on busy, rush-hour trains.

Only 68 percent of those who stand at times were satisfied with BART, while 78 percent of those who find seats said they were satisfied with the train service, the surveyors reported.

Ridership since the 2012 survey increased from 400,000 trips per day to 430,000 trips per day in 2014.

Two worker strikes that shut down the train system for several days in 2013 likely added to the discontent, officials acknowledged.

The written survey did not directly ask riders about the strikes, which stranded tens of thousands of train riders and worsened traffic congestion in the Bay Area, and the strikes weren’t among the top complaints mentioned in a comment section of the survey.

The top complaints there were the shortage of seats and the dirty chairs and carpets, said Aaron Weinstein, BART manager of marketing and research.

“(The strikes) were not among the top comments on the survey,” Weinstein said.

He linked the complaints about hot train car interiors to overcrowding and aging air conditioning systems.

While BART still enjoys high satisfaction ratings compared with the transit industry as a whole, board members said they are considering a variety of measures to make riders happier until 2016, when the first train cars in a new fleet are scheduled to arrive.

BART is also seeking grant funding to repair six cars damaged by fire and accidents so it can run longer trains, Trost said.

In spring, the train system expects to finish the Contra Costa Crossover project that provides side tracks near Pleasant Hill, enabling trains to turn around faster and more quickly reach areas with the most passengers.

The agency also is considering hiring more train shop workers to get cars back into service faster, Weinstein said.

As far as dirty seats and carpets, BART is making headway. It recently replaced the last of its hard-to-clean wool seat covers with easier-to clean plastic seat covers, and plans by June to finish replacing train car carpets with smooth synthetic flooring.

BART also is replacing electrical equipment on many cars to make air conditioners and heaters more reliable, officials said.

“We are trying to address these concerns as best we can in the short term until the arrival of fleet of the future provides more permanent relief,” Trost said.

Contact Denis Cuff at 925-943-8267. Follow him at Twitter.com/deniscuff