Montgomery County is no longer relying on the computer that crashed in November 2009, jumbling 800 traffic signals, creating gridlock and infuriating drivers for days.

The room-size computer installed in 1980 has been replaced by a new, $25 million system that's supposed to control the flow of traffic by adjusting green and red lights.

The new system was supposed to be installed by 2015, but after the crash, Montgomery County Executive Ike Leggett ordered the county to move faster.

"Every day, motorists in our region experience some of the worst gridlock in the nation, but without the county's active transportation management system, it would be far worse," Leggett said in a statement. "The new system is an essential part of the county's transportation network, cost-effectively balancing the needs of vehicles, pedestrians, bicyclists and transit."

Officials said it took nearly three years to replace the computer after the crash because they had to install new communications cables while ensuring the old ones continued to work.

The new system does the same thing as the old computer, but more reliably: It coordinates signals to keep traffic flowing. It keeps green lights on longer for commuters heading south into D.C. during rush hour, for example.

"[The old computer] served the county residents and the taxpayers very well, but it definitely needed to be upgraded," county spokeswoman Esther Bowring said.

Spare parts were hard to find, Bowring said. After the 2009 crash, engineers went searching for parts in a "kind of a junkyard for old computers."

The central computer was cutting-edge technology when it was installed 30 years ago, county officials said.

"At the time, it was high-tech and powerful," said Mike Kinney, a senior engineer with the county's transportation department. "No longer."

The county still wants to make an additional $10 million upgrade so signals stay on when power goes out. About 100 eight-hour batteries have been installed on county-owned signals so far, Kinney said. The work should be finished by late 2014.