4. Existing problems in current research

Tang and Song summarize the low-energy warm mix asphalt concrete construction technology in the application of G109 national highway rebuilding project and, through the experiment monitoring, found that after the application of the technology, mixing, transporting, and paving of the mixture temperature were signifi-

emissions, and effectively reducing the negative impact of the project which brings to the plateau fragile ecological environment [23]. Pan studied the life cycle energy consumption and carbon emission of highway. After modeling and quantitative analysis of energy consumption and greenhouse gas emissions in different stages of highway life cycle, the author thinks that the average annual energy consumption of cement concrete pavement is less than that of asphalt concrete pavement. Therefore, from the perspective of energy saving, cement concrete pavement is superior to asphalt concrete pavement [24]. Shi analyzed the energy consumption of asphalt pavement regeneration materials in road maintenance. After investigating the energy consumption of five different pavement materials in the four stages of raw material production, mixing plant, transportation, and construction machinery, it was found that the energy consumption of regenerative mixture is less. Therefore, from the perspective of energy saving, the regenerative technology is worth

Ma et al. evaluated the energy consumption of continuous reinforced concrete pavement and hot mix asphalt pavement in the construction process and made it clear that reducing the amount of early energy consumption in the production stage of raw materials in the pavement life cycle is conducive to promoting the sustain-

Li used LCA method to compare the environmental impact of continuous reinforced concrete pavement with asphalt pavement. The energy consumption and emission are quantitatively analyzed by selecting a reasonable calculation method for each stage. Among them, the calculation method of energy consumption includes quota method and IRI—speed—fuel consumption model. The results show that the green degree of continuous reinforced concrete pavement is higher than

Zhang et al. analyzed the influence of different asphalt structural layer design parameters on the carbon emission characterization results. The results show that the greenhouse effect is the most serious in the construction period of asphalt pavement, accounting for more than 95%, and the carbon emissions in the produc-

Due to the complexity of pavement system, problems still exist in the applica-

• There are many differences in the assumptions of system boundary and

• In the process of inventory analysis, the life stages considered in many

• Models and methods of life cycle assessment are not unified, lacking of consistent criteria for data analysis during the interpretation phase.

• Due to the opacity of domestic industry data, when the LCA method is applied in China, most of the list data are mostly directly from foreign literature or

able development of the highway engineering field [26].

tion stage have the greatest impact on the greenhouse effect [28].

database, so its reliability is difficult to be guaranteed.

that of asphalt concrete pavement [27].

Transportation Systems Analysis and Assessment

tion of LCA in China:

94

boundary conditions.

studies are not comprehensive.

cantly reduced, saving energy consumption, reducing the CO2 and smoke

spreading [25].

There are relatively few studies on the integrated evaluation methods of life cycle economic cost and environmental impact. For the research in this field, the economic cost and environmental impact of multiple schemes are usually calculated separately, and then the advantages and disadvantages of the schemes are compared by multi-objective optimization. Shu et al. firstly analyzed the differences between the two life cycle methods and introduced the basic principles and disadvantages of PTLaser and TCAce, two software platforms that integrate the two in foreign countries, so as to provide references for domestic researchers [29]. Batouli et al. evaluated the life cycle costs and environmental impacts of different pavement design schemes, and the results showed that the initial cost of flexible pavement was lower, but it would bring higher long-term costs and environmental impacts [30]. Umer et al. proposed a road scheme evaluation system, integrating LCCA and LCA, and carried out a multi-objective analysis based on economic cost and environmental impact. It is proved that geosynthetics can be used to improve the service life of low-traffic road surface and to minimize the cost and environmental impact.

In general, the research on the comprehensive evaluation of economic cost and environmental impact within the life cycle in China is still in the stage of independent research, lacking the integration and comprehensive use of the two.
