Analysis of Trends in Commuter Rail Energy Efficiency
Commuter rail systems are widely regarded as an effective transportation alternative to reduce energy consumption and emissions in large urban areas. Use of commuter rail systems in the United States is on the rise, with annual ridership increasing by 28 percent between 1997 and 2007 [1]. With growing concerns about the sustainability and environmental impacts of transportation, modal energy efficiency is increasingly considered amongst the metrics to evaluate the benefits and costs of transportation systems and justify future investment. To gauge the relative long-term efficiency trends for rail as an urban transportation mode, this study analyzes historic trends in energy efficiency metrics for US commuter rail systems. Commuter rail systems receiving, or benefiting from, Federal Transit Administration (FTA) grants are required to report operations and energy consumption data on an annual basis to the National Transit Database (NTD). NTD data on energy consumption, operations, and services supplied from 1997 to 2011 are analyzed to determine historic trends in various energy efficiency metrics for the commuter rail mode as a whole. The data analysis and comparison of the results with the highway mode is complicated by the use of electric traction by some commuter rail operators. These operators report energy consumption in purchased electricity (kWh) instead of gallons of liquid fuel. The different approaches that can be employed to compare these two forms of propulsion and their intrinsic efficiencies and energy sources are discussed. Energy efficiency of each commuter rail system and its relationship to individual system characteristics during the study period are also analyzed. Finally, case studies of historic energy efficiency of individual commuter rail systems with longer operating histories and reporting data over the majority of the study period are contrasted against more recent start-up systems. While many systems outperform the energy efficiency of a typical light-duty vehicle, there are others that, due to a variety of system parameters and characteristics, fail to achieve a load factor great enough to make them more attractive than the highway mode on a gross average level. It is hoped that highlighting trends and variation in commuter rail energy efficiency will allow policymakers to make more informed decisions regarding the environmental benefits of rail as an urban transportation mode.Copyright © 2014 by ASME
Multi-scale evaluation of diesel commuter rail fuel use, emissions, and eco-driving
Abstract Diesel commuter rail emissions affect populations near rail corridors. An approach is demonstrated to quantify mesoscale and microscale diesel commuter rail fuel use and emission rates (FUERs) of CO 2, CO, NOx , particulate matter , and total hydrocarbons based on two U.S. systems. A speed trajectory simulator, an energy model, and an emissions model were calibrated, evaluated, and applied. FUERs and potential reductions from eco-driving were quantified based on simulated trajectories. Hotspots were defined as sections with ≥ 90 th percentile of section-average FUERs by species. A few key variables explain 74–80% of variability in mesoscopic and microscopic FUERs. On average, FUERs are 7–8 times greater for hotspots than non-hotspots. Eco-driving was estimated to reduce segment-average FUERs by 3–33% and eliminate 2–11% hotspots. However, mesoscale oriented eco-driving can, at some locations, increase microscopic FUERs. The approach is adaptable to other diesel commuter rail systems.
Natural Radioactivity of Intrusive-Metamorphic and Sedimentary Rocks of the Balkan Mountain Range (Serbia, Stara Planina)
Stara Planina (also known as the Balkan mountain range) is known for numerous occurrences and deposits of uranium and associated radionuclides. It is also famous for its geodiversity. The geologic framework is highly complex. The mountain is situated between the latitudes of 43° and 44° N and the longitudes from 22°16′ to 23°00′ E. Uranium exploration and radioactivity testing on Stara Planina began back in 1948. Uranium has also been mined in the zone of Kalna, within the Janja granite intrusive. The naturally radioactive geologic units of Stara Planina are presented in detail in this paper. The main sources of radioactivity on Stara Planina can be classified as: 1. Granitic endogenous—syngenetic–epigenetic deposits and occurrences; 2. Metamorphogenic—syngenetic; and 3. Sedimentary, including occurrences of uranium deposition and fluctuation caused by water in different types of sedimentary rocks formed in a continental setting, which could be classified under epigenetic types. The area of Stara Planina with increased radioactivity (higher than 200 cps), measured by airborne gamma spectrometry, is about 380 square kilometers. The highest values of measured radioactivity and uranium grade were obtained from a sample taken from the Mezdreja uranium mine tailing dump, where 226Ra measures 2600 ± 100 Bq/kg and the uranium grade is from 76.54 to 77.65 ppm U. The highest uranium (and lead) concentration, among all samples, is measured in graphitic schist with high concentrations of organic (graphitic) material from the Inovska Series—99.47 ppm U and 107.69 ppm Pb. Thorium related radioactivity is the highest in granite samples from the Janja granite in the vicinity of the Mezdreja granite mine and the Gabrovnica granite mine tailing dump, and it is the same—250 ± 10 Bq/kg for 232Th, while the thorium grade varies from 30.82 to 60.27 ppm Th. In gray siltstones with a small amount of organic material, the highest radioactivity is related to potassium—2080 ± 90 Bq/kg for 40K.