The amount of pollution emitted by a vehicle depends on its load and speed, among other factors. This paper presents the Pollution-Routing Problem (PRP), an extension of the classical Vehicle Routing Problem (VRP) with a broader and more comprehensive objective function that accounts not just for the travel distance, but also for the amount of greenhouse emissions, fuel, travel times and their costs. Mathematical models are described for the PRP with or without time windows and computational experiments are performed on realistic instances. The paper sheds light on the tradeoffs between various parameters such as vehicle load, speed and total cost, and offers insight on economies of ‘environmental-friendly’ vehicle routing. The results suggest that, contrary to the VRP, the PRP is significantly more difficult to solve to optimality but has the potential of yielding savings in total cost.

The Pollution-Routing Problem

Existing automobile fuel consumption and emission models suffer from two major drawbacks; they produce a bang–bang control through the use of a linear power model and the calibration of model parameters is not possible using publicly available data thus necessitating in-laboratory or field data collection. This paper develops two fuel consumption models that overcome these two limitations. Specifically, the models do not produce a bang–bang control and are calibrated using US Environmental Protection Agency city and highway fuel economy ratings in addition to publicly available vehicle and roadway pavement parameters. The models are demonstrated to estimate vehicle fuel consumption rates consistent with in-field measurements. In addition the models estimate CO2 emissions that are highly correlated with field measurements.

Virginia Tech Comprehensive Power-Based Fuel Consumption Model: Model Development and Testing

Background, aim, and scope
Lightweight design is a common means of reducing a passenger car's fuel consumption. In order to calculate the resulting fuel savings, one has to estimate the total energy that is needed to move a certain weight over a defined distance in a distinct way, and express this energy in liter of gasoline or diesel. This can be accomplished by the so-called fuel reduction value (FRV) and based on a standardized driving cycle, e.g., the New European Driving Cycle (NEDC). The aim of this paper is to explain the theoretical background of the calculation of fuel savings in automotive lightweight life cycle assessments (LCAs) of internal combustion engine (ICE) vehicles in greater detail than it has been done before, to describe the resulting factors and their different applications, and to point out some notable particularities that need to be taken into account when conducting this type of LCA study.

On the calculation of fuel savings through lightweight design in automotive life cycle assessments

Freight transport has undesirable effects on the environment. The most prominent of these is greenhouse gas emissions. Intermodal freight transport, where freight is shipped from origin to destination by a sequence of at least two transportation modes, offers the possibility of shifting freight (either partially or in full) from one mode to another in the hope of reducing the greenhouse emissions by appropriately scheduling the services and routing the freight. Traditional planning methods for scheduling services in an intermodal transportation network usually focus on minimizing travel or time-related costs of transport. This article breaks away from such an approach by addressing the issue of incorporating environment-related costs (greenhouse gases, to be specific) into freight transportation planning and proposes an integer program in the form of a linear cost, multicommodity, capacitated network design formulation that minimizes the amount of greenhouse gas emissions of transportation activities. Computational results based on an application of the proposed approach on a real-life rail freight transportation network are presented.

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Minimizing greenhouse gas emissions in intermodal freight transport: an application to rail service design

Executive Order S-1-07, the Low Carbon Fuel Standard (LCFS) (January 18, 2007), calls for a reduction of at least 10 percent in the carbon intensity of California’s transportation fuels by 2020. It instructed the Secretary of the California Environmental Protection Agency to coordinate activities between the University of California and various state agencies to develop and propose a draft compliance schedule to meet the 2020 Target. This report is the first of two by the University of California in response. This first study assesses the low-carbon fuels options that might be used to meet the proposed standard, and presents a number of scenarios for mixes of fuels that might meet a 5, 10, and 15 percent standard. The second part of the study, to be released one month later, will examine key policy issues associated with the LCFS. On the basis of a study of a wide range of vehicle fuel options, we find a 10 percent reduction in the carbon intensity of transportation fuels by 2020 attainable, but an ambitious target. With some vehicle and fuel combinations, a reduction of 15 percent may be possible. All of the technical options to reduce GHG emissions from the transportation sector (e.g. biofuel production and electric vehicles) have technical and economic uncertainties that need further evaluation and research, but there are many different options, of which many show great potential to lower the global warming impact of transportation fuels. Many research and development efforts are already underway now to bring these advanced technologies to market. This diversity of low-carbon fuel and vehicle options leads to a simple conclusion that the California Air Resources Board should include the LCFS as an early action measure under AB 32 (Nunez/Pavley), the Global Warming Solutions Act.

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A Low-Carbon Fuel Standard for California, Part 1: Technical Analysis

Energy flows and energy efficiencies in the operation of a modern automobile are expressed in terms of simple algebraic approximations. One purpose is to make a car's energy use and the potential for reducing it accessible to non-specialists with technical backgrounds. The overall energy use depends on two factors, vehicle load and powertrain efficiency. The former depends on speed and acceleration and key vehicle characteristics such as mass. The latter depends on heat-engine thermodynamic efficiency, and engine and transmission frictions. The analysis applies to todays automobiles. Numerical values of important parameters are given so that the reader can make his or her own estimates. Various technologies to reduce the energy consumption of automobiles are discussed.

Marc Ross

Papers

Fuel efficiency and the physics of automobiles