We are doomed or the study is a fraud.
298 ships times 1 million cars per day. We should be choking on thick smog.
Total worldwide cruise capacity at the end of 2015 will be 486,385 passengers (a 7.3% increase over 2014) and 298 ships
http://www.cruisemarketwatch.com/capacity/
Which would roughly equal the amount of cars running in the USA daily. 298 million cars for a population of 320 million. I’m a little high on the number but I think we are good!