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41.
In modern cities, a rapid increase of motorcycles and other types of Powered Two-Wheelers (PTWs) is observed as an answer to long commuting in traffic jams and complex urban navigation. Such increasing penetration rate of PTWs creates mixed traffic flow conditions with unique characteristics that are not well understood at present. Our objective is to develop an analytical traffic flow model that reflects the mutual impacts of PTWs and Cars. Unlike cars, PTWs filter between cars, have unique dynamics, and do not respect lane discipline, therefore requiring a different modeling approach than traditional “Passenger Car Equivalent” or “Follow the Leader”. Instead, this work follows an approach that models the flow of PTWs similarly to a fluid in a porous medium, where PTWs “percolate” between cars depending on the gap between them.Our contributions are as follows: (I) a characterization of the distribution of the spacing between vehicles by the densities of PTWs and cars; (II) a definition of the equilibrium speed of each class as a function of the densities of PTWs and cars; (III) a mathematical analysis of the model’s properties (IV) an impact analysis of the gradual penetration of PTWs on cars and on heterogeneous traffic flow characteristics.The proposed model could contribute as an enabler for ‘PTW-aware’ future Cooperative Intelligent Transport Systems technologies and traffic regulations. 相似文献
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43.
Using input–output (I–O) accounts provided by the U.S. Department of Commerce, this study investigates the aggregate relationships
between the transportation and communications inputs demanded (directly and in total) by all industries in the U.S., and compares
the results across time. We analyzed five pairs of Spearman correlations of transportation and communications demands (utilities,
manufacturing, and overall) using the direct and total coefficient tables from the ten benchmark input–output years spanning
1947 to 1997. To correctly represent the overall economy-wide relationship, each industry (direct table) or commodity (total
table) in the correlation was weighted proportionately to the monetary value of its contribution to the U.S. economy. In the
analysis using direct I–O coefficients, we found a pattern of predominant complementarity between transportation and communications
manufacturing, and substitution between transportation and communications utilities. There are intriguing indications, however,
of a shift from substitution to complementarity in the latter case, beginning around 1987. In the analysis using total I–O
coefficients, we found a pattern of complementarity for all years between transportation and communications manufacturing,
and a pattern changing from substitution to complementarity for the remaining four pairs (transportation manufacturing and
communications utilities; transportation utilities and communications manufacturing; the utilities pair; and the overall pair).
Thus, from the industrial perspective (which constitutes a sizable proportion of the total demand for communications and transportation),
it is not realistic in modern times to expect telecommunications to substitute for travel. Nevertheless, further research
is needed into the specific causes of the observed shift from substitution to complementarity, and current trends should continue
to be monitored for any changes.
Taihyeong Lee is a Ph.D. candidate in civil and environmental engineering and a graduate student researcher of the Institute of Transportation Studies at the University of California, Davis. His research focuses on the study of travel behavior, and on the impacts of structural changes in industry on relationships between transportation and communications. Patricia L. Mokhtarian is a professor of civil and environmental engineering, associate director of the Institute of Transportation Studies, and chair of the interdisciplinary Transportation Technology and Policy MS/PhD program at the University of California, Davis. She specializes in the study of travel behavior, and of the impacts of information and communications technology on transportation. 相似文献
Patricia L. Mokhtarian (Corresponding author)Email: |
Taihyeong Lee is a Ph.D. candidate in civil and environmental engineering and a graduate student researcher of the Institute of Transportation Studies at the University of California, Davis. His research focuses on the study of travel behavior, and on the impacts of structural changes in industry on relationships between transportation and communications. Patricia L. Mokhtarian is a professor of civil and environmental engineering, associate director of the Institute of Transportation Studies, and chair of the interdisciplinary Transportation Technology and Policy MS/PhD program at the University of California, Davis. She specializes in the study of travel behavior, and of the impacts of information and communications technology on transportation. 相似文献
44.
This paper investigates temporal and weather-related variation in taxi trips in New York City. A taxi trip data-set with 147 million records covering 10 months of activity is used. It is shown that there are substantial variations in ridership, taxi supply, trip distance, and pickup frequency for different time periods and weather conditions. These variations, in turn, cause variations in driver revenues which is one of the main measures of taxi supply–demand equilibrium. The findings are then used to discuss the anticipated impacts of two recently enacted taxi regulation changes: the first fare increase since 2006 and the E-Hail pilot program which allows taxi hailing with smart phone applications. The fare increase is estimated to cause varying levels of revenue increase for different time periods. E-Hail apps are not expected to offer considerable improvements at all times, but rather when both adequate taxi supply and demand occur simultaneously. 相似文献
45.
Increasing concerns on environment and natural resources, coupled with increasing demand for transport, put lots of pressure for improved efficiency and performance on transport systems worldwide. New technology nowadays enables fast innovation in transport, but it is the policy for deployment and operation with a systems perspective that often determines success. Smart traffic management has played important roles for continuous development of traffic systems especially in urban areas. There is, however, still lack of effort in current traffic management and planning practice prioritizing policy goals in environment and energy. This paper presents an application of a model-based framework to quantify environmental impacts and fuel efficiency of road traffic, and to evaluate optimal signal plans with respect not only to traffic mobility performance but also other important measures for sustainability. Microscopic traffic simulator is integrated with micro-scale emission model for estimation of emissions and fuel consumption at high resolution. A stochastic optimization engine is implemented to facilitate optimal signal planning for different policy goals, including delay, stop-and-goes, fuel economy etc. In order to enhance the validity of the modeling framework, both traffic and emission models are fine-tuned using data collected in a Chinese city. In addition, two microscopic traffic models are applied, and lead to consistent results for signal optimization. Two control schemes, fixed time and vehicle actuated, are optimized while multiple performance indexes are analyzed and compared for corresponding objectives. Solutions, representing compromise between different policies, are also obtained in the case study by optimizing an integrated performance index. 相似文献
46.
Cities worldwide are implementing modern transit systems to improve mobility in the increasingly congested metropolitan areas. Despite much research on the effects of such systems, a comparison of effects across transit modes and countries has not been studied comprehensively. This paper fills this gap in the literature by reviewing and comparing the effects obtained by 86 transit systems around the world, including Bus Rapid Transit (BRT), Light Rail Transit (LRT), metro and heavy rail transit systems. The analysis is twofold by analysing (i) the direct operational effects related to travel time, ridership and modal shifts, and (ii) the indirect strategic effects in terms of effects on property values and urban development. The review confirms the existing literature suggesting that BRT can attract many passengers if travel time reductions are significantly high. This leads to attractive areas surrounding the transit line with increasing property values. Such effects are traditionally associated with attractive rail-based public transport systems. However, a statistical comparison of 41 systems did not show significant deviations between effects on property values resulting from BRT, LRT and metro systems, respectively. Hence, this paper indicates that large strategic effects can be obtained by implementing BRT systems at a much lower cost. 相似文献
47.
Assessment of economic impacts from unexpected events with an interregional commodity flow and multimodal transportation network model 总被引:1,自引:0,他引:1
Heejoo Ham Tschangho John Kim David Boyce 《Transportation Research Part A: Policy and Practice》2005,39(10):849-860
Loss and damage caused by unscheduled events, especially earthquakes, have sudden and significant impacts not only on the region’s economy where the event occurs but also on other regions. The New Madrid Seismic Zone, located in the center of the United States, could have great impacts on economic activities related to this area, if a major earthquake occurred. Based on the 1993 US Commodity Flow Survey [US Commodity Flow Survey, 1993. Available from: <http://www.bts.gov/ntda/cfs/prod.html>], more than 42% of total commodity flows in the US are related to the greater Midwest, which includes the New Madrid Seismic Zone. If a catastrophic earthquake occurred in this area, the indirect damages could spread far beyond the region, and could have sizable impacts on other regions. A model of interregional commodity flows, incorporating regional input–output relationships, and the corresponding transportation network flows, was applied to assess the economic impacts of such an unexpected event. The economic impacts from the event are described for three hypothetical scenarios, analyzing the magnitude and the extent of the direct and indirect impacts. These analytical results may be used to propose strategic management of the recovery and reconstruction efforts after the event. 相似文献
48.
Coral reefs are threatened by impacts such as from scuba diving, and ongoing research is required to assess diving impacts, diver behavior and environmental knowledge. This study investigated perceived diving impacts, reef condition and norms among scuba divers at Sodwana Bay (South Africa). Divers viewed contact with coral as damaging, and perceived environmental degradation at dive sites. However, most divers saw activities such as photography as causing little or no damage to reefs. One meter or less was believed to be a safe distance from the reef or the wildlife to avoid contact or disturbance, and encounter norms were high. Age and experience influenced most perceptions, although cannot be accepted as reliable indicators of divers' perceptions or behavior, due to the heterogeneous conduct of divers of various experience and age as described in literature. The importance of human perceptions to understand what strategies need implementation in diving management is discussed. 相似文献
49.
This paper is part of ongoing research on incorporating environmental aspects in microscopic integrated land use/transport models. The long-term goal is to add scenario sensitivity for noise emissions in a new modeling suite. Therefore, as a first step, the influence of simulated car traffic noise on real rent prices in the study area in question is analyzed and compared to existing studies. It is shown that modeled noise values from the transportation model are able to explain significant impacts on rent prices when using a hedonic pricing regression. When using noise as a continuous variable, price discounts of 0.4% per dB(A) are found. A discount of up to 9.6% for particularly loud locations is estimated when noise is used as a categorical variable. Care should be taken when controlling for accessibilities that may correlate with noise. The results are in line with results of previous studies and confirm that environmental aspects can and should be considered in integrated models. 相似文献
50.
Grant Murray 《Coastal management》2013,41(2-3):339-355
Although coastal tourism is often looked to as a way of generating foreign revenue, it can also engender a range of social and environmental impacts. From an historical perspective, this article examines the growth of Cancún in the Mexican state of Quintana Roo since the late 1960s. The article documents a range of socioeconomic and environmental impacts associated with the rise of coastal tourism, and suggests that centralized planning and the provision of physical and financial infrastructure does not prevent those impacts. The principal causes of these impacts are also described, including changes in land-usage, population, tourism markets, foreign market penetration and control, an emphasis on short-term economic gain, weak regulatory enforcement, and an overall lack of integration of coastal zone management. 相似文献