The logistics of evacuating a major city are complex.  The evacuation of New Orleans during Katrina ran surprisingly smoothly, with very few traffic accidents or fatalities, causing few resulting traffic backups.  The evacuation plan enacted was the result of two less successful evacuations for hurricanes Georges and Floyd, both of which fortunately passed east of the city.  Committees of people went to work trying to improve the evacuation plans to allow everyone to get out of the city in the fastest and most efficient way possible.  The result was the creation of contraflow patterns for traffic in the city.  There were also some issues with getting everybody out of the city because a lot of people did not own a car or were elderly and could not evacuate.  Another major issue was a failure of communication.  There was no way for officials to know which routes out of the city were backed-up and which routes were flowing freely (Wolshon, 2004).

There are many different factors to take into account when trying to create an evacuation plan.  In New Orleans, the exit capacity is roughly 67% (American Highway Users Alliance, 2006), which means that if all of the evacuation goes smoothly, the roads outside of New Orleans will only be able to evacuate two-thirds of the population in twelve-hours.  The city with the best exit capacity is Kansas City, with 98% (American Highway Users Alliance, 2006) of the people able to leave the city in the peak twelve hours.  To improve New Orleans, there would have to be wider roads with more entrance and exit points to prevent bottlenecking on the major highways. 

    Another useful figure that ties in with exit capacity is the internal traffic flow.  This is a measure of traffic within the city during an evacuation.  It is based on the average travel delay time during an evacuation.  New Orleans did fairly well in this category with an average travel delay time of about 19%, corresponding to an internal traffic flow rating of 81% (American Highway Users Alliance, 2006).  This is measured with the Travel Time Index, which uses the ratio of the commute in an evacuation to the time that it takes to travel that distance on any normal day (Bureau of Business Research, 2006).  In the case of New Orleans, it takes about 19% more time to travel from one part of town to the other when there is an evacuation going on then when there is no significant traffic.

The final major factor in determining the overall evacuating capacity of a city is the percentage of people who have access to a car.  This does not mean that they own a car.  It only means that they can find a ride out of the city, either with a neighbor, family member, or a friend.  In New Orleans, about 91% of the population has access to a car (American Highway Users Alliance, 2006). 

Finally, all of these factors are averaged together with different weights to calculate the evacuation capacity of New Orleans.  This figure is used to rank New Orleans amongst other major towns.  In a study of thirty-seven major cities with a population of over one million people, New Orleans ranked twelfth with an evacuation capacity of 67.3% (American Highway Users Alliance, 2006).  This number represents the likely percentage of people who will be able to evacuate New Orleans in the peak twelve hours of the evacuation process.  Another figure that can be calculated is the roadway capacity, or the percentage of people who can theoretically evacuate the city if the roads were the only limiting factor.  This is found by averaging the internal traffic flow and the exit capacity to get 74%, which is higher than the evacuation capacity because the evacuation capacity takes into account the people who do not have cars (American Highway Users Alliance, 2006).

There are many ways to improve evcauation capacity when rebuilding New Orleans.  One option is to widen the highways from four to six lanes.  Evacuating the city is a difficult situation because New Orleans is bounded on the north by the lake, which limits the routes out.  Consideration of public transportation as an integral part of evacuating is another option.  There are nine percent of people without cars who still need a way to evacuate, so it makes sense to enlist the help of buses.  Another possibility is to look into creating safe shelters within the city limits.  This gets rid of the need to bus people long distances out of the city, which puts less of a strain on the public transportation (American Highway Users Alliance, 2006).  There is all ready the Superdome, which could easily be reinforced and more prepared to serve as an emergency shelter.

Overall, New Orleans already has a functioning evacuation capacity, but it can be improvedt.  During Katrina, the people who evacuated did so with very few problems.  The major issue right now is to understand why people could not or did not evacuate the city.   To keep New Orleans safe, it is necessary to continue to improve the evacuation plan so that moves everyone to safety.