The U.S. Defense Advanced Research Projects Agency has completed the first citywide assessment of its SIGMA radioactive threat detection system.

SIGMA is designed to aid defense personnel with responding to potential nuclear and radiological threats such as dirty bombs. The recent deployment test involved 1,000 detectors and over 100 mobile sensors, marking the largest demonstration of its kind in the program's history.

"The SIGMA system performed very well, and we collected and analyzed a huge amount of streaming data as we watched in real-time as participants covered a large portion of D.C.," DARPA program manager Vincent Tang said in a press release. "The data collected is already proving invaluable for further development of the system, and we're excited that SIGMA is on track to provide U.S. cities an enhanced layer of defense against radiological and nuclear threats."

During the test, several hundred volunteers equipped with smartphone-sized radiation detectors were tasked with walking around Washington, D.C. to search for simulated threats, which included small quantities of radioactive material.

The detectors used in the scenario do not emit radiation, and convey information using networked smartphones. Volunteers in the test carried detectors in backpacks, allowing SIGMA researchers to assess their functionality.

DARPA officials say they plan to continue test the program using citywide scenarios in the future, and upgrade to wide-area monitoring in 2017. The agency hopes to transition the operational system to local, state and federal entities in 2018.