Development of a Model for Freeway Green Landscape Evaluation

Abstract

The freeway green landscape is an important part of freeway systems, as the landscape provides a scenic view and performs other functions, such as preventing glare in median areas, enhancing a soil stability in slope embankment areas, and protecting ecology in roadside areas. Traditionally, the green landscape has been evaluated on the basis of the quality of the scenic view without consideration of the functional quality. This paper summarizes a research project to develop procedures and models for the evaluation of the freeway green landscape. The main evaluation indices considered in the evaluation procedures and models are the antiglare capability in median areas, the enhancement of soil stability in slope embankment areas, and the protection of ecology in roadside areas. In addition, quality of the landscape scenic view is another important factor that affects green landscape quality. The main purpose of the models is to convert evaluation indices to an overall quality measure that represents the overall quality of the freeway green landscape. The conversion is based on multivariable regression models and expert opinion survey models. Field data were collected by field survey-ors, who collected index data and a panel that provided subjective ratings of the green landscape in the median, slope embankment, and roadside areas. Both data sets were used for regression analysis and modeling purposes. Conversely, an expert opinion survey was conducted to obtain subjective opinions on the model weights. The models developed were validated by objective and subjective methods. The validation results show a strong correlation between the subjective evaluation and the objective evaluation: the models are effective and reasonable. In the past 18 months, these models have been used in practical applications, and the models' good applicability has been proved.