There is anecdotal evidence based on an informal count of trucks on the NJ turnpike showing an increase in truck traffic. I warn you, this informal study reported on CNBC is about as informal and non scientific as you can get however when you tie it to other evidence (i.e, FEDEX financial results - profit doubles) you see some coalescing evidence that the economy is picking up and trucks are moving.
However, if you take the comments by FEDEX CFO Alan Graf at his word, evidence is the economies of the world are not growing fast enough to offset things such as high unemployment
There is a mixed bag I guess. I chose to believe the former rather than the later.