I want to know the answer to the following question:
When did the Nanjing Yangtze River Bridge first open for traffic?
All the background I'm provided with is that "Begun in 1960 and opened to traffic in 1968, the bridge is a two-tiered road and rail design spanning 4,600 metres on the upper deck, with approximately 1,580 metres spanning the river itself.". Is that enough to answer the question?