This project arises due to the need to reduce environmental impact caused by drayage trucks from the ports of Los Angeles and Long Beach operating with freight transportation to warehouses in California. For this purpose, the study is focused on the analysis on I-710, the main freeway that links the port area with Los Angeles, which has become the major source of air pollution, caused mainly by diesel trucks. To reduce these levels of contamination, the I-710 Corridor Project includes a Clean Truck Incentive Program to encourage fleet turnover from diesel to Zero Emission / Nearly Zero Emission trucks. To demonstrate that these funded trucks are going to provide the necessary emission reduction benefits, the vehicle miles traveled (VMT) on I-710 must be determined.
The main objective of this project is to develop a study method that allows analysis of drayage truck flows on I-710 from a raw GPS trace data set. The project is divided in two parts. The first part consists of converting GPS traces into a set of potential loading and unloading stops made by trucks. Determining these origins and destinations allows for the calculation of routes taken on the California road network, and consequently the analysis of
their routes on I-710. The second part involves developing a custom Iterative Proportional Fitting (IPF) method, which allows scaling number of trips in the GPS data sample to total trips, according to a simulation model based on travel demand activity.
The results obtained through utilizing trip length distributions have shown that the methodology developed for calculating routes and the customized method of the IPF are valid for route analysis. Although the methodologies employed have been shown to be feasible, it has been found that the available GPS dataset is not representative enough to perform the VMT analysis on I-710. Therefore, the results obtained as shown in this project
are only illustrative due to these limitations of the sample. This is detected when, after scaling trips, the scaled GPS data sample only represents 10% of total miles traveled on I-710, so it does not allow reliable results to be obtained.
The conclusions obtained are based on the fact that the study methods developed are valid to obtain analysis of the routes on the road network and also on I-710. But it is detected that reliable results cannot be obtained because the GPS data have oversampled the short trips and therefore are not representative of total population. With a larger data sample with a greater number of trips on I-710 (that ITS-Irvine researchers are currently in negotiations to obtain) it is believed that the developed methodologies could be applied to obtain useful results with high degree of confidence.
