Positive train control (PTC) technology is in the testing phase, in revenue service demonstration or fully operational on 30 percent of the 3,339 miles of commuter rail in the United States, the American Public Transportation Association (APTA) announced yesterday. In addition, U.S. commuter railroads have installed 81 percent of the 15,192 pieces of onboard equipment needed for PTC. They've also installed 79 percent of PTC-related track equipment, APTA officials said in a press release. What's more, 61 percent of commuter railroad employees have been trained on PTC, while 70 percent of the necessary back-office control systems are ready for operation. U.S. commuter railroads have acquired 88 percent of the radio spectrum required for PTC. The achievements demonstrate "steady progress" in implementing the train control technology in 2018's first quarter, APTA officials said. However, commuter railroads have faced "significant financial constraints and technical challenges" in rolling out PTC. Implementing the technology on commuter railroads is expected to exceed $4.1 billion. Federal law requires railroads to implement their PTC systems by Dec. 31. However, they can qualify for two-year extension if they meet certain requirements, such as installing all PTC hardware, acquiring needed spectrum and training employees. Since mandating PTC in 2008, the federal government has provided just $272 million in PTC grants for commuter railroads — more than 70 percent of which was awarded last year, APTA officials noted. "Beyond the considerable financial constraints, the technical challenges related to PTC implementation have been significant for commuter railroad agencies," they said. "A limited number of PTC-qualified vendors are simultaneously in demand by both the passenger and freight rail industries to develop, design, and test this complex safety technology." Other remaining challenges include diagnosing and resolving software issues, securing track access and achieving interoperability with other railroads, according to APTA. In March, the U.S. Government Accountability Office reported that as many as two-thirds of the 29 commuter railroads required to implement PTC might not meet the Dec. 31 deadline or qualify for the extension.