Enablers and Barriers to the Adoption of Alternatively Powered Buses

Abstract

This paper seeks to identify enablers and barriers that stimulate or prevent the adoption of alternatively powered buses (APBs) in cities. The research method concentrates on an in‐depth analysis of 21 European demonstration case studies of APBs. Considerable differences exist between these cities due to the different reference situation. The type of measurement and the situation in the demonstration cities influence the exact fuel consumption and emission reduction. Variables that could enable the adoption of all types of APBs are: (1) the compatibility with previously introduced ideas; (2) the already available necessary supporting infrastructure in the city; (3) a changed external appearance of the APB; (4) the acceptance of the APBs by passengers and bus drivers; and (5) political support in the city regarding the APBs. The main variables that could be determined as barriers are: the relative economic advantage (the outline of costs is higher than that of conventional buses); and the understanding of the APB for bus drivers and mechanics (because special training is needed for both groups).     

Do Public Transport Improvements Increase Agglomeration Economies? A Review of Literature and an Agenda for Research

Public transport improvements may increase economic productivity if they enable the growth and densification of cities, downtowns, or industrial clusters and thereby increase external agglomeration economies. It has been argued that the potential agglomeration benefits are large; if so, understanding them better would be useful in making funding decisions about public transport improvements. We reviewed theoretical and empirical literature on agglomeration as well as a small number of articles on transportation's role in agglomeration. The theoretical literature is useful in understanding possible avenues by which transportation improvements might affect agglomeration, although there is little discussion of public transport specifically. Relevant empirical studies tend to focus on metropolitan regions and use a generalized measure of transportation cost. But public transport impacts on agglomeration are likely to be different from road investment impacts. We identified several ways of conducting research building on this literature that would help evaluate the agglomeration impacts of public transport proposals: tracing the links between transport, agglomeration, and productivity; better motivating research using theories of agglomeration mechanisms; taking scale and redistribution into account; exploring the functional form of agglomeration economies; accounting for endogeneity in model structure; and considering development context.     

Evaluating employer programs encouraging the use of alternate transportation modes: Two studies

Since 1976, major Denver metropolitan area firms have been required to encourage employees to use mass transit, carpooling, bicycling, and other alternate transportation modes to commute to work. The encouragement programs of 36 firms were clearly associated with greater use of alternate transportation modes, with the portion of variance in alternate transportation use explained by differences in employer programs of approximately 15%. The effects of the programs on deterring alternate mode users from returning to solo driving are consistently weaker than their effects on persuading drivers to try alternate transportation modes initially. Recommendations for the conduct of alternate transportation encouragement programs are made, based on these and other results. In addition, two recommendations are made concerning the evaluation of encouragement programs: that aggregate percentage change in alternate transportation use should not be used as the sole measure of success, and that environmental variables such as the availability of and pressure for use of alternate transportation modes should be measured and controlled.     

On the definition of traffic equilibrium

Three alternative definitions of traffic equilibrium are compared in terms of the mechanisms of route-choice inherent in them. These definitions are the usual Wardrop equilibrium and user-optimised ones and a new one. Conditions on the cost function are established under which the Wardrop definition is equivalent to each of the other two. Some circumstances are identified in which these conditions are satisfied. A detailed discussion is given of an example in which these conditions are not satisfied and the three definitions are not equivalent.     

Collecting longitudinal data from freight operators: survey design and implementation ideas and challenges

Freight transport research has generally been limited by a lack of data of the breadth and quality available for passenger transport, particularly in terms of behavioural data. This paper discusses the survey design and implementation of a survey intended to collect longitudinal behavioural data on the responses of freight transport firms to environmental policies. The design of the survey is centred around a hypothetical scenario where respondents are asked how they would complete a given freight task within common constraints. One of the key components of the survey design is a dynamic component intended to simulate the changing business environment. The paper illustrates the many challenges in getting complex freight related surveys in the field.     

The effect of uncertainty on US transport-related GHG emissions and fuel consumption out to 2050

The future of US transport energy requirements and emissions is uncertain. Transport policy research has explored a number of scenarios to better understand the future characteristics of US light-duty vehicles. Deterministic scenario analysis is, however, unable to identify the impact of uncertainty on the future US vehicle fleet emissions and energy use. Variables determining the future fleet emissions and fuel use are inherently uncertain and thus the shortfall in understanding the impact of uncertainty on the future of US transport needs to be addressed. This paper uses a stochastic technology and fleet assessment model to quantify the uncertainties in US vehicle fleet emissions and fuel use for a realistic yet ambitious pathway which results in about a 50% reduction in fleet GHG emissions in 2050. The results show the probability distribution of fleet emissions, fuel use, and energy consumption over time out to 2050. The expected value for the fleet fuel consumption is about 450 and 350 billion litres of gasoline equivalent with standard deviations of 40 and 80 in 2030 and 2050, respectively. The expected value for the fleet GHG emissions is about 1360 and 850 Mt CO₂ equivalent with standard deviation of 130 and 230 in 2030 and 2050 respectively. The parameters that are major contributors to variations in emissions and fuel consumption are also identified and ranked through the uncertainty analysis. It is further shown that these major contributors change over time, and include parameters such as: vehicle scrappage rate, annual growth of vehicle kilometres travelled in the near term, total vehicle sales, fuel economy of the dominant naturally-aspirated spark ignition vehicles, and percentage of gasoline displaced by cellulosic ethanol. The findings in this paper demonstrate the importance of taking uncertainties into consideration when choosing amongst alternative fuel and emissions reduction pathways, in the light of their possible consequences.     

Economic value and utility of a powertrain system for a plug-in parallel diesel hybrid electric bus

This research is the first to develop a design for a powertain system of a plug-in parallel diesel hybrid electric bus equipped with a continuously variable transmission (CVT) and presents a new design paradigm of the plug-in hybrid electric bus (HEB). The criteria and method for selecting and sizing powertrain components equipped in the plug-in HEB are presented. The plug-in HEB is designed to overcome the vulnerable limitations of driving range and performance of a purely electric vehicle (EV) and to improve fuel economy and exhaust emissions of conventional bus and conventional HEBs. The control strategy of the complicated connected propulsion system in the plug-in parallel HEB is one of the most significant factors in achieving higher fuel economy and lower exhaust emissions of the HEV. In this research, a new optimal control strategy concept is proposed against existing rule-based control strategies. The optimal powertrain control strategy is obtained through two steps of optimizations: tradeoff optimization for emission control and energy flow optimization based on the instantaneous optimization technique. The proposed powertrain control strategy has the flexibility to adapt to battery SOC, exhaust emission amount, classified driving pattern, driving condition, and engine temperature. The objective of the optimal control strategy is to optimize the fuel consumption, electricity use, and exhaust emissions proper to the performance targets. The proposed control strategy was simulated to prove its validity by using analysis simulation tool ADVISOR (advanced vehicle simulator).     

Torsional stiffness and weight optimization of a real bus structure

In this paper, the structural optimization of a real bus structure is proposed. The proposed optimization has been accomplished by means of genetic algorithms. The structural behavior of the bus structure when subjected to weight and torsion was also analyzed using the finite element method (FEM). The results demonstrate that improved weight and torsional stiffness are achieved with the optimized structure.     

Performance of radial-type metal foam diesel particulate filters

An analytical study of the performance of a radial-type, metal foam diesel particulate filter is reported. A mathematical model for the filtration and regeneration of soot in a metal foam filter was developed. Nickel foam was selected for the filter medium due to its large specific area, high porosity, and high thermal resistance. For various metal foams, the filtration efficiency and the pressure drop through the filter were calculated, as was the deposition of soot. The results from the analytical model were compared with experimental data. In comparison with a conventional wall flow filter, the metal foam diesel particulate filter (DPF) is effective in utilizing the volume of material, due to the porous structures. As the size of the metal foam pores in the DPF increases from 580 μm to 800 μm, the filtration efficiency decreases from 90% to 50%, and the pressure drop decreases from 380 mbar to 20 mbar. The metal foam DPF with a large pore size is effective in utilizing the volume of material with a small pressure drop. The regeneration is completed within four minutes by the flow of hot exhaust gases under full load conditions.     

Minimizing vehicle post impact path lateral deviation using optimized braking and steering sequences

This paper investigates the optimal control of a vehicle, after a light impact during a traffic accident. To reduce the risk of secondary events, the control target is set: to minimize the maximum lateral deviation from the initial path. In previous analysis path control was achieved by the active control of individual wheel braking. The present paper examines potential benefits from the additional control of front steering angles. Numerical optimization is used to determine optimal control sequences for both actuator configurations. It is found that steering provides significant control benefits, though not for all post-impact kinematics. For all cases considered, the optimal control operates at the boundary of the control domain of available forces and moments. This domain is expanded when steering is available, and there exists an expanded range of conditions for which coupled control of yaw moments and lateral forces is the most effective control strategy. The sensitivity of vehicle response to the individual actuator controls is studied; it reveals this sensitivity is related to the actuator bandwidth and the lack of any dynamic cost in the longitudinal direction. This motivates a further analysis which includes longitudinal and lateral dynamics in the cost function. This is broadly related to real-world crash risks. Further, different versions of such cost functions are compared as a basis for implementation in a closed-loop controller.