A Look at Traffic

Case studies to allow an analysis of traffic.

Saturday, May 30, 2009

The Flux of LA Over the summers from 2003-2008

In this case study, I wanted to look at the net flux of L.A. over the summer months. To do this I treated the Los Angeles Area as a "black box" thus only looking at the main highways going into and out of the LA area. For each year I took data using PEMS, It was taken between Memorial day and Labor day. The exact dates are Memorial Day and Labor day are listed here:

May 23rd, 2003 and September 1st, 2003
May 28th, 2004 and September 6th, 2004
May 27th, 2005 and September 5th, 2005
May 26th, 2006 and September 4th, 2006
May 25th, 2007 and September 3rd, 2007
May 23rd, 2008 and September 1st, 2008

Each of these consists of 101 days which allows for the tail end of the data to be a little off. Although this is not perfect, it does work out quite well for comparing July 4th traffic in the region for each of the years studied.

As a macroscopic study, the aterial streets or much smaller highways are essentially ignored. My choice on highways was generally chosen by looking at maps.google.com. The exact location was determined based on two things. 1) The location of the least amount of major highways pulling off the highway I was studying. Essentially looking for the "neck" of the bottle neck and 2) The amount of accurate data I could find from the PeMS data loop counters. I looked for a high observance percentage. However, I should note, that some summers only provided me with 0% observance ratio, thus giving data that is only a guess at best and leaves some of the charts lacking accurate data. The loop detectors on some highways were only recently installed, and data in the region was simply just unavailable. Here is a map of where the loop detectors I used are located. Notice they tried to surround the L.A. region as best as possible.

View Traffic Study - LA Flux over summer Loop Locations in a larger map

Once each location had been determined and data was collected for the inbound and outbound directions for the years 2003 - 2008, I was ready to calculate Net Flux!
Flux in this study will simply be defined as the the amount of cars that flows on a highway over the summer months. The Net flux is simply the difference between the amount of cars going into L.A. subtracted from the amount of cars leaving the L.A. area. I should note that this can be a positive or negative number. If their are more cars leaving the L.A. area, then we would have a negative number. On average, however we normally have more cars entering LA then leaving LA, leaving the net flux to be a positive number. Here we see the data for each of the years.

Key: Light Blue - 2003, Red - 2004, Orange - 2005, Green - 2006, Darker Blue - 2007, Purple - 2008. Note: the time scale in the graph shows it is 2003, However, this is only because there must be a year associated with these dates. Simply ignore the year 2003 scaling of the graph. This graph shows the Net volume of vehicles driving into the LA study area (positive values) or leaving the LA study area (negative values).

Data Analysis Conclusions
Now that we have collected all the data, and organized it in a coherent way so it can be displayed on a graph, we can begin to draw some conclusions about the L.A. area during the summers between 2003 and 2008. The first thing the data shows us is that we have higher traffic volumes in the years 2003,2004,2005 and 2006 then we do in 2007, and 2008. This maybe linked to higher gas prices during the 2007 and 2008 time period.
Also notice the traffic on the 4th of July. There is typically a decline around this time in each of the years. Possibly people are relaxing after lighting up the sky. Later in the month of July we see low volumes of traffic during the middle of the month. This could be the reason for choosing to close the 405 freeway for construction in 2011. Towards the end of our study period we see traffic volumes pick up quite a bit. Three day weekends sometimes start early with eager travelers looking for an extended vacation to leave the LA area.


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