Research On OD Synthesis Technique In A Large Area

Roadside interview OD survey is often used to obtain vehicle OD table on highway in large area in China. The roadside interview OD survey in a large area often has many roadside interview spots, very complex highway network and many routes between origins and the destinations. How to get a precise OD table from the roadside interview OD survey data is very important. Based on the study of OD synthesis theories all over the world, a new method, "Routs Enumerating Method", is presented to synthesize OD table basing on route choice theory from a roadside interview OD survey in a large area. This method uses two ways to get volume on all routs: one is to get volume directly from the survey data; the other is to evaluate the volume on some routs. The author also provides a method for renewing the synthesized OD table to minimize the difference between the counted volume and the assigned volume on some road segments without changing the original OD table too much. And this method combines OD table synthesizing and traffic assignment as a whole. This paper also discusses interview spots arrangement's influence on the synthesized OD table and provides a new method for choosing interview spots' sites in the situation of having no transcendental traffic model. And then the author programs to make this method become a part of TransCAD. The author also discusses the sample rate's influence on the OD table of a single roadside interview spot, calculates the sample rates in the situation of different volume and different error using the 0-1 distribution theory, analyses the efficiency of different sample methods. Finally, the method of OD table synthesis and OD renewal are put into practice to synthesize OD table from Hebei Province highway OD survey data. The result indicates that the above methods can get very precise OD table.