The U.S. Department of Transportation reports today that: “U.S.–Canada surface transportation trade totaled US$537 billion in 2008, up 5.1 percent compared to 2007. The value of imports carried by truck was 6.0 percent lower in 2008 than 2007 while the value of exports carried by truck was 2.4 percent higher.” That would be $1.5 billion worth of goods that's going back and forth over the world's longest undefended border every day, most of which — 60 per cent — is being borne on the back of a truck. About 17 per cent of the value of that trade came and went by train and 16 per cent came and went by pipeline.
Speaking of which: The U.S. imported US$82 billion worth of goods — oil and natural gas mostly — via pipeline but exported just US$4.3 billion worth of pipeline material. The U.S. also received much more in Canadian imports by rail than exports but more goods flowed from the U.S. into Canada by truck — $179 billion — than flowed the other way – $141 billion.
The Michigan-Ontario border points were tops with $67-billion worth of goods going back and forth through 2008.