A second tube opened to the north in 1945 .
The tunnels only had a combined capacity of 15 million vehicles per year , and by 1949 , the tubes were already carrying 11 million annual vehicles .
A second tube opened to the north in 1945 , but the tunnels only had a combined capacity of 15 million vehicles per year , and by 1949 , the tubes were already carrying 11 million annual vehicles .