Transportation Research Record: Journal of the Transportation Research Board

FTA provides guidance for the evaluation of impacts to a variety of noise-and vibration-sensitive uses along a rail transit system. Included under the category of special buildings are concert halls or sound-recording facilities and auditoriums. The impact criteria for ground-borne noise from the transit systems into such spaces are maximum noise levels of 25 or 30 dBA, respectively, far more restrictive than for any other category considered in the FTA Guidance Manual. Conformance with these impact criteria is necessary to avoid significant impact during environmental analysis but may not be a sufficient evaluation of the effect of the transit systems. Some special parameters that should be considered for any rail transportation project that seeks to become a close neighbor of such facilities are discussed.

In cooperation with FHWA, the Arizona Department of Transportation initiated a program to reduce highway traffic noise in the Phoenix, Arizona, metropolitan area by overlaying many freeway segments constructed of transversely tined portland cement concrete pavement with an asphalt rubber friction course. The acoustic performance of this noise mitigation approach was documented with three types of measurements: tire–pavement noise source levels, short-term neighborhood noise measurements, and roadside noise measurements at research sites. Initial comparison of the noise reductions produced by the asphalt rubber friction course indicated good agreement between the Type 1 and Type 3 measurements. Reductions for the Type 2 measurements were about 3 to 4 dB lower on average than were the other two types. Almost all of the Type 2 locations had features that provided noise reduction prior to the overlay. The effect of these features on the Type 2 noise reductions were examined using a research version of the FHWA Traffic Noise Model that accounts for differences in tire–pavement noise source levels. With the use of Type 1 data and the characteristics of the Type 2 sites, it was found that when the effect of the reduced tire–pavement source strength was added to the already existing noise-reducing features, the predicted reductions were consistent with the Type 3 results. In this sense, Type 2 and Type 1 results were found to correlate with each other and, by extension, to the Type 3 results.

The vibration forces generated by train wheels rolling on steel rails are characterized as the force density level (FDL). FDLs are a key component in predicting vibration levels from future train projects and generally are assumed to be independent of the measurement position and the soil properties. FDLs are dependent on several factors, which include track type, vehicle suspension systems, train speeds, and condition of wheels and rail surfaces. Presented are results of train vibration measurements at three sites in Seattle, Washington, along Sound Transit's Central Link, and a comparison of the results with previous FDL results from Central Link's start-up phase. The effects of speed, train length, and track type on FDLs were measured. A test train was employed for the measurements at three sites. The tests at the three sites also included supplemental measurements with revenue service trains. The study showed that the vibration of the current Sound Transit fleet was lower than the previous measurements apparently because the wheels were in better condition than for the earlier tests. Rail roughness was also measured at all the test sites, and their effects on FDL were explored.

In NCHRP Project 10–76, methodologies were developed and demonstrated for evaluating the feasibility, reasonableness, effectiveness, acoustic longevity, and economic features of pavement strategies and barriers proposed for highway noise abatement. The essential elements of the methodologies are the use of an expanded pavement life-cycle cost analysis to examine economic features, a modified version of FHWA's Traffic Noise Model to integrate the noise reducing performance of pavements and barriers, and the use of onboard sound intensity data as input to the prediction model. The developed methodology is applied to state project–based examples. Barriers, quieter pavement, and combinations of both are evaluated for feasibility and reasonableness using the policies of three state highway agencies.

With the booming natural gas trade, liquefied natural gas (LNG) carriers—the primary transportation method for intercontinental trade on natural gas—have been experiencing enormous growth. This study offers a novel analysis that connects 2011's in-use LNG fleet characteristics, global satellite data on ship movement, and literature on LNG trade to assess the long-term prospects for increasing the energy efficiency of LNG carriers. This analysis also investigates how efficiency characteristics (such as age, size, technology, and operational practices) influence the efficiency of the LNG fleet and develops a ship stock model to independently track technical and operational efficiency practices in LNG carriers. The findings indicate that industry-leading LNG carriers are about 40% more efficient than industry laggards. This analysis indicates that by fully embracing the available technical and in-use practices of the low-carbon industry leaders of today, the fleet could reduce CO₂ emissions by 30 million metric tons by 2040—about 8 million metric tons of natural gas, equivalent to $4 billion savings in the LNG supply chain. This study has important implications for the shipping industry and policy makers. The industry has to address split incentives to take advantage of energy-saving opportunities. Regulations that set targets for the energy efficiency of the in-use fleet may ultimately help the industry harvest the efficiency gains while mitigating climate impact from the industry.

This study examined bus drivers' acceptance of fuel cell electric buses in Alameda–Contra Costa Transit in the San Francisco Bay Area of California. Of the 145 surveys issued, 47 drivers completed a written survey, for a 32% response rate. The study focused on a key attribute for potential success of alternative urban bus technology: the driver acceptance factor. Technology performance flaws that are undesirable or annoying to the bus drivers may also be disruptive to passengers. Furthermore, because of using the buses throughout their full duty cycle, drivers are in a unique position to identify key opportunities to improve the new technology options as they emerge and evolve. The study found that drivers, in general, rated the hydrogen fuel cell buses to be at the same or better performance than diesel buses for handling, ride quality, acceleration, and braking. For quiet operation, the drivers rated the new buses as excellent. When asked how they liked the experimental hydrogen fuel cell buses, drivers responded at just above neutral, with the most common response being “the same” as diesel buses followed by “much better.” Those drivers who said that they considered fuel economy when purchasing a vehicle liked the fuel cell buses more. Older drivers preferred the diesel buses, and male drivers preferred the new fuel cell buses. Perceptions of safety were mixed, with some drivers expressing safety concerns independent of how much training they had received.

Cities are developing greenhouse gas (GHG) mitigation plans and reduction targets on the basis of a growing body of knowledge about climate change risks, and changes to passenger transportation are often at the center of these efforts. Yet little information exists for characterizing how quickly or slowly GHG emissions reductions will accrue given changes in urban form around transit and whether benefits will accrue quickly enough to meet policy year targets (such as reaching 20% of 1990 GHG emissions levels by 2050). Achieving GHG reductions through integrated transportation and land use planning is even more complicated for cities because changes in emissions can occur across many sectors (such as transportation, building energy use, and electricity generation). With the use of the Los Angeles, California, Expo Line, a framework was developed to assess how financing schemes could affect the rate of building redevelopment and resulting life-cycle GHG emissions from travel and building energy use. The framework leveraged an integrated transportation and land use life-cycle assessment model that captured upfront construction of new development near transit and the long-term changes in household energy use for travel and buildings. The results show that for the same amount of development around the Expo Line, it is possible either to meet state GHG goals by 2050 (if aggressive redevelopment happens early) or not meet those goals by 2050 (if significant redevelopment does not start for decades). The time-based approach reveals how redevelopment schedules should be considered when strategies for meeting future GHG emissions targets are set.

Changes in travel behavior near the Sheppard Subway Line in Toronto, Ontario, Canada, and the associated greenhouse gas impacts were examined. A study looked at initial changes in mode share after the line opened in 2002 and examined ongoing mode share trends through 2012. The initial mode shift was assessed through an analysis of bus boardings, subway platform counts, and traffic counts made between 2000 and 2012. Longitudinal changes in mode share were assessed with the use of transit survey data. For the first 6 years of operation, the Sheppard Subway Line produced more greenhouse gas (GHG) per passenger kilometer traveled (PKT) than the bus that it had replaced. A net GHG reduction of 66.4 kilotons of CO₂ equivalent was calculated but was wholly dependent on avoided car PKTs that may have been offset in their entirety by induced travel on Sheppard Avenue.

Vehicle fuel economy improvement has proved to be one of the most effective policies in controlling gasoline demand and greenhouse gas emissions in the transportation sector. However, such improvement also results in the decrease of fuel tax revenue, the main funding source for building and maintaining the U.S. transportation infrastructure. Conversely, fuel efficiency improvement reduces the marginal and average cost of travel, thus encouraging drivers to drive more, and that in turn increases gasoline consumption. The objective of this study was to estimate the potential loss of fuel tax revenue and greenhouse gas emissions, dependents of fuel consumption, that resulted from the fuel efficiency improvement. Accordingly, fuel consumption was modeled as a system of equations consisting of vehicle miles traveled and fuel efficiency (in mpg) as two explanatory variables. The model was estimated by the three-stage least squares method, with annual time-series data for Washington State over the period from 1976 to 2011. According to the results, Washington State will have a $106 million loss in revenue and an 8.7% reduction in emissions of carbon dioxide (CO₂) in 2031.

Compared with traditional vehicles, light-duty battery electric vehicles (BEVs) currently have price premiums and noncost limitations, such as reduced range, sparse public recharging infrastructure, and long recharge times. These additional limitations can be captured in different ways in a consumer choice model. Three approaches are implemented to noncost barrier modeling, and results are compared. A penalty approach quantifies limitations as additional costs to the consumer, and two threshold approaches determine BEV suitability by the frequency that daily driving distance exceeds the vehicle range. GPS-based trip data are used to form ensemble distributions of low-, medium-, and high-intensity driving distances to support the analysis. All approaches show limited (5%) adoption of BEVs by 2050, and the BEV mileage fraction trails the stock fraction because of the use of substitute vehicles for high-mileage trips and adoption biased toward lower driving intensity segments. In fact, a majority of the electrified miles driven stem from plug-in hybrid electric vehicles, not BEVs. Of the BEVs, the powertrains offering 150- to 250-mi ranges are responsible for more than 50% of sales. Results also hint that longer-range BEVs act as primary household vehicles, but lower-range BEVs serve as secondary household vehicles. A parametric exploration shows that mechanisms to mitigate the hardship of the noncost barriers can significantly increase adoption rates but that reducing battery price alone does not. However, these mechanisms can be different for different modeling approaches.

A sustainable biofuel supply chain must be not only economically viable but also environmentally benign. This study addressed a strategic multistage expansion (e.g., a decade) of a cellulosic biofuel supply chain system with supplements of corn grain biofuels. A multiobjective, multiyear optimization framework was proposed, and the compromise method was used to seek best-compromise solutions between economic competitiveness and environmental quality of the supply chain while satisfying evolving fuel demand, feedstock resources, and technological constraints. The model was implemented in an illustrative case study of planning an in-state ethanol supply chain in California between 2015 and 2025. The results indicated that significant trade-offs existed between cost and greenhouse gas emissions in the supply chain and that cellulosic ethanol produced from corn stover and forest residues could be an important alternative to corn ethanol with a low cost of $2.20/gal and emissions of 1.5 carbon dioxide equivalent kg/gal.

Comparisons are reported on the simulated fuel economy for parallel, series, and dual-mode hybrid electric long-haul trucks, in addition to a conventional powertrain configuration, powered by a commercial 2010-compliant 15-L diesel engine over a freeway-dominated heavy-duty truck driving cycle. The driving cycle was obtained by measurement during normal driving conditions. The results indicated that both parallel and dual-mode hybrid powertrains were capable of improving fuel economy by 7% to 8%. However, there was no significant fuel economy benefit for the series hybrid truck because of internal inefficiencies in energy exchange. When reduced aerodynamic drag and tire rolling resistance were combined with hybridization, there was a synergistic fuel economy benefit for appropriate hybrids that increased the fuel economy benefit to more than 15%. Long-haul hybrid trucks with reduced aerodynamic drag and rolling resistance offered lower peak engine loads, better kinetic energy recovery, and reduced average engine power demand. Thus, it is expected that hybridization with load reduction technologies offers important potential fuel energy savings for future long-haul trucks.

The amount of woody biomass available for biofuel production depends on tree growth rate, harvesting techniques, harvest cost, government policies, and established traditions within the industry. Comparing estimates of biomass availability across studies is difficult because of different methodologies for estimating biomass supply, compounded by inconsistent and often unspecified assumptions. Studies differ in their definition of biomass (i.e., tree size, parts of tree) and consideration of ecological and economic factors (i.e., harvest productivity and costs, competing demand, compliance with existing regulations). In particular, existing restrictions on bio-mass harvesting for biofuels under the Federal Renewable Fuel Standard often are not included. Additionally, because most biomass availability studies ignore current biomass uses, an overestimation of available bio-mass for future uses results. Presented are new estimates for the amount of economically available biomass in Maine, taking into consideration both economic (integrated harvesting for pulp and precommercial thinning) and ecological factors. It is found that biomass availability varies greatly, depending on the relative location of the biorefinery, biomass harvesting site, and existing wood consumers (e.g., pulp mill). Indeed, harvesting and transporting woody biomass without an existing use for the high-value forest products (saw logs and pulp) probably makes woody biomass for energy production uneconomical. This finding is contrary to some existing studies and suggests that economic consideration needs greater emphasis in estimating biomass availability for biofuels.

To anticipate the impacts of electric vehicle (EV) charging on grid systems and the effectiveness of demand response measures for load control, it is critical to understand the determinants of EV charging demand. Previous research suggests that these determinants include both observable patent metrics of travel demand and less easily measurable triggers of charging decisions (such as range appraisal or habit). Nevertheless, analyses accounting simultaneously for both aspects are lacking. Data are used from a survey administered to EV drivers participating in the Low Carbon London EV trial to explore charging decision triggers to test their predictive power of observable metrics of charging demand, while controlling for variability in travel patterns. Results show that charging demand is significantly affected by travel pattern metrics as well as charging decision triggers.

Electric vehicles (EVs) offer significant opportunities to improve sustainability of the road transport sector. But simultaneously, widespread adoption of EVs would create new challenges. For example, spatiotemporal concentration of charging events in high-density residential or commercial areas would place extreme demands on the power network, causing bottlenecks and grid instability. A novel approach to the typical decentralized control methods for EV charging service providers (CSPs) is presented. First, static price signals based on anticipated demand define a set of charging offers, targeted to segments of EV users. Prices are differentiated either only by time or both by time and place and allow comparison and evaluation of both scenarios. A choice-based revenue management method is employed to optimize allocation of generated charging offers, with respect to revenue outcome for the CSP. The charging coordination techniques are demonstrated through simulation. Data come from the London Travel Demand Survey and particularly trips around Westfield, one of Europe's largest urban shopping malls, representing out-of-home charging behavior for short intervals in a high-demand area. Findings suggest that in a first-come, first-served system, locational pricing might create opportunities both for increased revenue and for relocation of charging events to less-congested facilities. In the revenue management system, locational pricing significantly favors total revenue outcome but without discharging vulnerable areas. However, because agents with conflicting interests participate in the process (infrastructure owners, power system operators, EV drivers), opportunity exists for the CSP to adapt constraints according to the priority of its objectives.

Presented is a tool to estimate fast charger demand and sample results on a current and future battery electric vehicle (BEV) scenario. The results highlight the data and methods needed to plan for fast charger demand. To plan for existing BEVs, origin and destination data are necessary for identifying which traffic is relevant to assess fast-charging demand. Also, as the battery size for BEVs increases, demand shifts from primarily inside metro areas to long-distance corridors outside metro areas. The sample results show the interactions of battery size, frequency of charging, and energy needed per charge. Although energy per charge increases with battery size, overall electricity demand per vehicle decreases with larger batteries.

Advance mitigation is a process through which the environmental impacts and required mitigation are assessed for one or more transportation projects early in project planning and development. The approach enables mitigation to be planned, commenced, and completed earlier; applies regionally or programmatically across multiple projects; and takes ecosystem- and landscape-level concerns into account. Although there have been efforts to develop programmatic mitigation initiatives and funding to support them, there is little documentation of their establishment, operation, or accomplishments. A study documents and analyzes 10 prominent California experiences with advance mitigation undertaken by the state department of transportation in coordination with regional councils, local governments and transportation agencies, and environmental groups. Each effort is profiled, including the origin of the mitigation effort; its location, scale, and cost; its specific connection to transportation projects; funding, revenue sources, or financial options used to support it; key institutional partners; and lessons learned from the experience. California's initiatives offer some lessons: external conservation planning efforts can play a significant role in creating both momentum and structure for comprehensive mitigation planning; transportation-related advance mitigation is necessarily a highly interdependent undertaking, involving not only the state department of transportation and other transportation project sponsors but also federal and state natural resource agencies as well as local environmental groups; and the long-time horizons of advance mitigation planning and the complex nature of infrastructure development bring unavoidable uncertainty to such efforts and demand flexibility from mitigation partners in the process.