Photo by Michael Farquhar.

A day after passengers aboard a Red Line train struggled to reach the operator while they witnessed a brawl in their car, Metro concluded that the intercoms in scores of its cars need upgrades. Moreover, the transit agency found that the problems with the intercom systems have been under investigation for months.

In short, the issue arose because two classes of rail car, the 1000 series and 4000 series, are incompatible with newer 6000-series cars, which often serve as train leads. When a 6000-series car heads up a tail of older cars, its more advanced electronic systems cannot connect to the communications systems in the rest of the train, leading to incidents like Monday’s when passengers could not alert their driver that a dangerous brawl was in progress.

In order to avoid more events like this Metro will have to tinker with the 184 cars in its 6000-series fleet. To communicate with the 4000-series vehicles, the newer cars just need a software upgrade. But in order for the modern cars to connect with the 1000 series, which dates back to the system’s founding, Metro technicians will have to install new components into the 6000-series cars’ control panels.

Metro currently has enough parts to fix up the first 20 modern cars. In a news release, the transit agency says it will take 45 days for all the upgrades to be complete, though there is no exact timetable for when the work will take place.