Norman Joseph Woodland and Bernard Silver developed the modern barcode, and were granted a patent for it in 1952. The idea was to make the checkout of articles easier, using a code which was inspired by Morse code. In 1959, David Collins developed a system for tracking railroad carriages which used barcodes. This system was unreliable, because of dirt on the barcodes. In the 1970s, the system was abandoned, but in the 1980s, a similar system which used radio tags was introduced.