In the wake of all the criticism of public officials and their responses to hurricane Katrina, I have been nagged by the logistical problem of moving the population of an entire city on short notice.
Here in the United States, we lack adequate public transportation, so the population must be evacuated mainly via private vehicles travelling on freeways. Under that assumption, how long will it take to evacuate a major metropolitan population of 3 million people?
Follow this link and you will find some quick numbers I crunched using some basic assumptions. There you’ll also find a link to an Excel spreadsheet that you can download and play with the numbers yourself. According to my calculations, it will take at least 25 hours to evacuate 3 million people, assuming perfect conditions (i.e. no traffic collisions and everyone goes at 60 mph). My calculations are based on passenger vehicles only, so I believe that 25 hours is extremely optimistic, as there will likely be a good number of trailers, trucks, and RVs that will consume more freeway space. According to this article, 2000 cars per hour each lane is an acceptable number of cars, which is slightly less optimistic than my 2263 cars per hour at 60 mph.
Getting back to the subject of Katrina, I would like to address the criticism aimed at the mayor of New Orleans for not busing the population out using the city’s large fleet of school buses. In light of the freeway capacity statistics, I don’t believe it would have been possible to move everyone out using school buses. Aside from the logistical problems of fuel, food, restrooms, and health care, it simply isn’t possible to move that many people away from a hurricane in a timely fashion. Had supplies been trucked into New Orleans immediately following the hurricane, the Superdome would have been a prudent place to shelter residents who had no means to leave the city.




