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111.
Intelligent transportation systems have been promoted as a means to improve both the efficiency and safety of the road network. The effectiveness of advanced technologies in improving road safety has been an area of research which has thus far yielded mixed results. In order to ensure that advanced technologies deliver on their intended outcomes, more research has to be devoted to understanding road users' perceptions and reactions to these systems. This study examines drivers' perceptions of the use of dynamic message signs and their self‐reported reactions to the messages displayed. In general, drivers support the use of highway electronic boards for traffic incident reports and weather information which have an impact on traffic delays and level of service. They also think that it is a good idea to display road safety messages and to remind drivers to drive safely and be courteous on the roads. Moreover, most drivers reported that they do read and think about the messages displayed and react positively to some of the road safety messages. 相似文献
112.
Deconstructing development density: Quality, quantity and price effects on household non-work travel
Smart growth and transit-oriented development proponents advocate increasing the density of new land development and infill redevelopment. This is partly in order to reduce auto use, by reducing distances between trip origins and destinations, creating a more enjoyable walking environment, slowing down road travel, and increasing the market for transit. But research investigating how development density influences household travel has typically been inadequate to account for this complex set of hypotheses: it has used theoretically unjustified measures, has not accounted for spatial scale very well, and has not investigated potentially important combinations of measures. Using data from a survey of metropolitan households in California, measures of development density corresponding to the main hypotheses about how density affects travel—activity density affecting distance traveled, network load density affecting the speed of auto travel, and built form density affecting the quality of walking—are tested as independent variables in models of auto trip speed and individual non-work travel. Residential network load density is highly negatively correlated with the speed of driving, and is also highly correlated with non-work travel, both singly and in combination with other measures. Activity density and built form density are not as significantly related, on their own. These results suggest that denser development will not influence travel very much unless road level-of-service standards and parking requirements are reduced or eliminated. 相似文献
113.
Konstantinos G. Zografos Konstantinos N. Androutsopoulos Teemu Sihvola 《Transportation》2008,35(6):777-795
Flexible transport services include a wide range of demand responsive transport systems that provide non-conventional passenger
and freight transportation services. Several alternative business models varying according to the local market conditions,
the socio-economic, legal, and institutional framework may be developed for the provision of Flexible Transport Systems (FTS).
The objective of this paper is twofold: first to present an integrated methodological framework for developing and assessing
alternative FTS business models and second to demonstrate its applicability to a case study regarding the prioritization of
alternative FTS business models for the provision of flexible passenger transport services in Helsinki.
相似文献
Teemu SihvolaEmail: |
114.
Using latent class cluster analysis, this paper investigates the spatial, social, demographic, and economic determinants of
immigrants’ joint distribution among travel time, mode choice, and departure time for work using the 2000 Census long form
data. Through a latent tree structure analysis, age, residential location, immigration stage, gender, personal income, and
race are found to be the primary determinants in the workplace commute decision-making process. By defining several relatively
homogeneous population segments, the likelihood of falling into each segment is found to differ across age groups and geography,
with different indicators affecting each group differentially. This analysis complements past studies that used regression
models to investigate socio-demographic indicators and their impact on travel behavior in two distinct ways: (a) analysis
is done by considering travel time, mode choice, and departure time for work simultaneously, and (b) heterogeneity in behavior
is accounted for using methods that identify different groups of behavior and then their determinants. Conclusively the method
here is richer than many other methods used to study the ethnically diverse population of California and shows the addition
of geographic location and latent segment identification to greatly improve our understanding of specific behaviors. It also
provides evidence that immigrants are as diverse as the non-immigrant population and transportation policies need to be defined
accordingly.
相似文献
Konstadinos G. GouliasEmail: |
115.
B. Blanco A. Alonso L. Kari N. Gil-Negrete J. G. Giménez 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(4):529-552
The finite length nature of rail-pad supports is characterised by a Timoshenko beam element formulation over an elastic foundation, giving rise to the distributed support element. The new element is integrated into a vertical track model, which is solved in frequency and time domain. The developed formulation is obtained by solving the governing equations of a Timoshenko beam for this particular case. The interaction between sleeper and rail via the elastic connection is considered in an analytical, compact and efficient way. The modelling technique results in realistic amplitudes of the ‘pinned–pinned’ vibration mode and, additionally, it leads to a smooth evolution of the contact force temporal response and to reduced amplitudes of the rail vertical oscillation, as compared to the results from concentrated support models. Simulations are performed for both parametric and sinusoidal roughness excitation. The model of support proposed here is compared with a previous finite length model developed by other authors, coming to the conclusion that the proposed model gives accurate results at a reduced computational cost. 相似文献
116.
Donghoon Kim Stephen Sungsan Park Choongsik Bae 《International Journal of Automotive Technology》2018,19(1):1-8
Three visualization methods, Schlieren, Shadowgraph, and Mie-scattering, were applied to compare diesel and gasoline spray structures in a constant volume chamber. Fuels were injected into a high pressure/high temperature chamber under the same in-cylinder pressure and temperature conditions of low load in a GDCI (gasoline direct injection compression ignition) engine. Two injection pressures (40 MPa and 80 MPa), two ambient pressures (4.2 MPa and 1.7 MPa), and two ambient temperatures (908 K and 677 K) were use. The images from the different methods were overlapped to show liquid and vapor phases more clearly. Vapor developments of the two fuels were similar; however, different liquid developments were seen. At the same injection pressure and ambient temperature, gasoline liquid propagated more quickly and disappeared more rapidly than diesel liquid phase. At the low ambient temperature and pressure condition, gasoline and diesel sprays with higher injection pressures showed longer liquid lengths due to higher spray momentum. At the higher ambient temperature condition, the gasoline liquid length was shorter for the higher injection pressure. Higher volatility of gasoline is the main reason for this shorter liquid length under higher injection pressure and higher ambient temperature conditions. For a design of GDCI engine, it is necessary to understand the higher volatility of gasoline. 相似文献
117.
P. Weston G. Yeo E. Stewart 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2015,53(7):1063-1091
This paper presents a view of the current state of monitoring track geometry condition from in-service vehicles. It considers technology used to provide condition monitoring; some issues of processing and the determination of location; how things have evolved over the past decade; and what is being, or could/should be done in future research. Monitoring railway track geometry from an in-service vehicle is an attractive proposition that has become a reality in the past decade. However, this is only the beginning. Seeing the same track over and over again provides an opportunity for observing track geometry degradation that can potentially be used to inform maintenance decisions. Furthermore, it is possible to extend the use of track condition information to identify if maintenance is effective, and to monitor the degradation of individual faults such as dipped joints. There are full unattended track geometry measurement systems running on in-service vehicles in the UK and elsewhere around the world, feeding their geometry measurements into large databases. These data can be retrieved, but little is currently done with the data other than the generation of reports of track geometry that exceeds predefined thresholds. There are examples of simpler systems that measure some track geometry parameters more or less directly and accurately, but forego parameters such as gauge. Additionally, there are experimental systems that use mathematics and models to infer track geometry using data from sensors placed on an in-service vehicle. Finally, there are systems that do not claim to measure track geometry, but monitor some other quantity such as ride quality or bogie acceleration to infer poor track geometry without explicitly measuring it. 相似文献
118.
119.
R. Pastres C. Solidoro S. Ciavatta A. Petrizzo G. Cossarini 《Journal of Marine Systems》2004,51(1-4):179
The paper aims at investigating the trends of the concentrations of dissolved inorganic nitrogen (DIN) and phosphorous in the Lagoon of Venice, Italy, in the last 35 years. The trend analysis of ammonia nitrogen, nitrate nitrogen and reactive phosphorus (RP) yielded rather different results. The decrease in ammonia nitrogen concentration, in particular, in the basin influenced by severe industrial discharges, is accurately described by a negative exponential model. The nitrate concentration did not show significant interannual trends, while wide seasonal variations have been detected. Reactive phosphorus concentration increased until the end of the 1970s at the stations close to the industrial area as well as in those influenced by river discharges and by sewages of the city of Venice. The sudden decrease that followed was most likely related with environmental policies, namely the improvement of wastewater purification treatments and the regulation of phosphorus use in detergents. 相似文献
120.
A. G. Thompson B. R. Davis 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,39(3):245-253
Summary Matrix expressions are developed for the direct computation of rms values for the optimal control forces, front and rear suspension strokes and dynamic tyre deflections in a half-car model on a random road of given roughness. A quadratic performance index is employed with assumed weighting factors and evaluated in the same computation. 相似文献