Calculating the Contribution Rate of Intelligent Transportation System in Improving Urban Traffic Smooth Based on Advanced DID Model

Table 9

Meanings of variables and indicators.

Main variable	Variable declaration
Decision variable	ASPD
Explanatory variable	CVECH
Control variable	RODM, GDP
Policy variable	means after the implementation of ITS project (2011-2012); means before the implementation of ITS project (2008~2010)
Category variable	means the objects of experimental group; means the objects of control group