This paper presents the basic concept and the field test results of the augmented data transmission (ADT) to increase the data capacity of the Advanced Television Systems Committee (ATSC) terrestrial DTV system. The ADT system can offer an additional data of rate up to a few megabits per second (Mbps) based on hierarchical modulation, DTV signal cancellation, and advanced error correction code. For the field test, the field strength and the required carrier to noise ratio (CNR) for a stable reception were measured at each test point. According to the field test results, when the ADT signal is injected 21 dB below the existing DTV signal, ADT system offers an additional broadcasting link supporting up to 2 Mbps data rate which is about 3 dB worse than the conventional DTV system.