Abstract
Predicting vehicle carbon emissions on vertical curve sections can provide guidance for low-carbon vertical profile designs. Given that the influence of vertical curve design indicators on the fuel consumption and CO2 emissions of vehicles are underexplored, this study filled this research gap by establishing a theoretical carbon emission model of vehicles on vertical curve sections. The carbon emission model was established based on Xu’s vehicle energy conversion model, the conversion model of energy, fuel consumption, and CO2 emissions. The accuracy of the theoretical carbon emission model and the CO2 emission rules on vertical curve sections were verified by field test results. Field tests were carried out on flat sections, longitudinal slope sections, and various types of vertical curve sections, with five common types of vehicles maintaining cruising speed. The carbon emission rate effects on the vertical curve are closely related to the gradient and irrelevant of the radius. On the vertical profile composed with downhill/asymmetric/symmetrical vertical curve with a gradient greater than the balance gradient, the carbon emission rate is determined by the gradient and radius. The influence of the gradient on carbon emissions of vehicle on these vertical profiles was more significant than the radius. The radius is irrelevant to the carbon emission rate on the other forms of vertical profile. These results may benefit highway designers and engineers by providing guidelines regarding the environmental effects of highway vertical curve indexes.
Highlights
Global warming caused by CO2 emissions is an environmental issue of urgent public concern. e vertical curve is an important part of the vertical profile section of the highway and affects emission properties, such as carbon emissions, in motor vehicles
Scholars dedicated to quantifying vehicle carbon emissions have established various microcarbon emission models including the Mobile Source Emissions Factor Model (MOBILE) [7], Comprehensive Modal Emissions Model (CMEM) [5], International Vehicle Emissions Model (IVE) [2], and Motor Vehicle Emissions Simulator (MOVES) [3] to reflect the real-time operating conditions of vehicles. e databases for these models were established based on laboratory dynamometer tests
Methods e methodological process that was used in this study is shown in Figure 1. e basic approach used to establish the theoretical carbon emission model of vehicles on vertical curves was deductive. e derivation began with basic cases of a vehicle moving on a level, uphill, or downhill section under the vehicle energy conversion model proposed by Xu et al [9, 10]. e results for those cases were generalized
Summary
Received 13 April 2020; Revised 27 June 2020; Accepted 24 July 2020; Published 29 August 2020. Predicting vehicle carbon emissions on vertical curve sections can provide guidance for low-carbon vertical profile designs. Given that the influence of vertical curve design indicators on the fuel consumption and CO2 emissions of vehicles are underexplored, this study filled this research gap by establishing a theoretical carbon emission model of vehicles on vertical curve sections. E accuracy of the theoretical carbon emission model and the CO2 emission rules on vertical curve sections were verified by field test results. E carbon emission rate effects on the vertical curve are closely related to the gradient and irrelevant of the radius. E influence of the gradient on carbon emissions of vehicle on these vertical profiles was more significant than the radius. E radius is irrelevant to the carbon emission rate on the other forms of vertical profile. On the vertical profile composed with downhill/ asymmetric/symmetrical vertical curve with a gradient greater than the balance gradient, the carbon emission rate is determined by the gradient and radius. e influence of the gradient on carbon emissions of vehicle on these vertical profiles was more significant than the radius. e radius is irrelevant to the carbon emission rate on the other forms of vertical profile. ese results may benefit highway designers and engineers by providing guidelines regarding the environmental effects of highway vertical curve indexes
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