Metrorail's main radio system is as old as the transit system itself, and that's creating confusion that could complicate emergencies.

Investigators found that Metro's command center couldn't adequately communicate with operators whose trains were stuck underground during January's Green Line meltdown, when hundreds of riders evacuated dark, hot trains on their own initiative.

That's because Metro's railcars have three analog radio channels, each of them used for a different section of the rail system. Metro's command system could not talk to trapped operators during the Jan. 30 emergency without interruption as they were on the same channel that other operators were using to make routine reports on other lines, officials said at a recent briefing.

Metro spokesman Dan Stessel said Metro officials have considered ways to fix the problem, but adding a fourth "incident" channel would be a challenge since each rail car would have to be retrofitted.

"What was talked about as part of the [Green Line] investigation was: Can we provide an incident channel, either through a wired deployment of digital radios, which is a possibility, or retrofitting the railcars to allow for a fourth or more channels?" Stessel said.

Metro is currently adding digital radio capabilities to its rail cars, Stessel said, and those digital radios will provide many more channels.

Metro has faced problems with its radios for years, plagued by dead zones and tunnels with little cellphone service for backup. The radios failed on Halloween 2011 when a fight broke out at the Foggy Bottom station. In 2010 a Maryland agency cited Metro in the deaths of two workers hit by track equipment and recommended the transit agency eliminate dead zones in its radio system.

But agency spokesman Philip Stewart said Metro monitors dead zones and tries to fix them, and Stessel said the dead zones have been reduced over the past two years.

"Anytime you have radio waves in a tunnel environment, the potential for locations with less-than-optimal coverage exists. We actively monitor for these areas and take appropriate action when they are reported," Stewart said in an email.