UPDATE — Tuesday — 6/16/2015, 9:00 a.m. EDT

DC’s Department of Transportation has provided comment on the following story, and disputes some of the claims made by Cesar Cerrudo. Read a new story, containing DDOT’s comments here.

EARLIER — Monday — 6/15/2015, 7:29 a.m. EDT

WASHINGTON — Traffic lights in the District and other major cities have been hacked by security researchers, in an attempt to point out vulnerabilities in infrastructures that support daily commutes.

Cesar Cerrudo, an Argentine security researcher at IOActive Labs, realized he could turn red lights green and green lights red, during a trip to Washington last year.

Cerrudo told The New York Times he could have paralyzed emergency responders, or shut down all roads to the Capitol.

Instead, Cerrudo contacted the company that designs city traffic sensors, but does not encrypt the data running through them.

“Cities are filled with security problems that could have a very direct and physical impact on our lives,” Cerrudo told the Times.

Cerrudo is bringing together security researchers in the public and private sector, to work on instituting encryption and passwords in connected cities, where traffic, water, waste and air management and the electric grid all have vulnerabilities.

Previous computer bugs in traffic systems resulted in San Francisco’s public train system trapping passengers underground, and Los Angeles, where hacked traffic lights clogged roadways for days.