Muni is seeking a contractor to redo its real-time bus information system, replacing the antiquated NextMuni displays that have flickered from San Francisco transit shelters since 1999.

If all goes as planned, the new signs would be a far cry from the current screens, which are often broken or inaccurate.

“The No. 1 complaint we get is their reliability,” said Ed Reiskin, director of the San Francisco Municipal Transportation Agency, which oversees Muni. “Either the sign shows a bus that doesn’t come, or doesn’t show a bus that comes.”

NextMuni “was an amazing leap” when Muni debuted it nearly two decades ago on the 22-Fillmore line, said Cheryl Brinkman, who chairs the SFMTA Board of Directors.

At that time, the agency wowed riders with the promise of satellite-tracking equipment to locate vehicles and send electronic signals to bus-shelter placards — a new form of whiz-bang technology created by the Emeryville startup NextBus. Muni officials hoped to offer the technology on portable gadgets that were in vogue at the time, such as desk clocks or pagers.

Over the years, the scheduling system slowly evolved. Engineers figured out how to monitor every vehicle’s position and reroute buses to prevent service gaps.

And they made the technology portable. NextBus makes its own smartphone app and provides open-source data for other companies to use.

But NextMuni also lagged behind other developments in GPS technology. Some Muni riders say the next amazing leap is long overdue.

Muni’s wish list for the new displays includes bus-crowding alerts, alternative routes when buses are late and, of course, better predictions for bus arrivals. The signs would use liquid crystal displays that allow text and graphics —an improvement over the current text-only LED signs.

Those perks will go a long way toward keeping people on old-fashioned mass transit, even as it faces competition from ride-hail services like Uber and Lyft, Reiskin said.

Rachel Hyden, head of the San Francisco Transit Riders advocacy group, was particularly excited about the addition of alternative routes.

“This is exactly what transit riders need,” she said. “Not everyone knows Muni well enough to know that if your bus is late, you can walk one or two blocks and catch another bus” going the same way.

“Now we’ll have more options,” Hyden said.

The request for proposals, which goes out Wednesday, calls for a contractor to create signs for 850 bus shelters, as well as software to power those signs and feed the various apps that riders use to predict bus arrivals.

To prepare, the MTA conducted surveys of 5,856 customers last year. The surveys showed that they are willing to wait 10 to 15 minutes for a bus without knowing when it will show up. Presented with a 20-minute wait, many customers will look for another route, and some will opt for a ride-hail service.

It will take several months to approve the six-year contract — which has to go through the MTA and the San Francisco Board of Supervisors — but the agency hopes to have every sign replaced by 2020, and the whole system remade by 2022. SFMTA could extend the contract for two additional five-year terms.

In the meantime, Hyden hopes Muni will fix all the broken signs and make sure the predictions are accurate in its existing system.

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: @rachelswan