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541.
In most developed countries motorized transportation is the dominant form of travel for long and short journeys. Transport-related
physical activity (TPA), however, is advocated as an appropriate transport mode for traveling short distances. The purpose
of this study is to explore the associations between private automobile availability, overall physical activity levels, and
TPA engagement in the adult population. A population-representative telephone survey assessed socio-demographics, private
automobile availability, overall physical activity levels, and travel to place of work/study and the convenience shop with
an adult sample (n = 2,000) residing in North Shore City, Auckland, New Zealand in April 2005. The majority of respondents reported unrestricted
(80%) or frequent (12%) private automobile availability. After controlling for covariates, binary logistic regression analyses
revealed those with no private automobile available were less likely to be classified as sufficiently active for health benefits
when compared to respondents with unrestricted private automobile availability. However, this finding was based on a small
minority (4%). Also, those reporting no private automobile availability were more likely to walk or cycle to place of employment
and the convenience shop when compared to those with unrestricted private automobile availability. Similar to other self-report
travel and physical activity survey tools, the questionnaire used potentially did not adequately capture TPA engagement. Future
TPA research needs to incorporate objective measures to address this issue.
相似文献
Hannah M. BadlandEmail: |
542.
This paper presents a comprehensive econometric modelling framework for daily activity program generation. It is for day-specific
activity program generations of a week-long time span. Activity types considered are 15 generic categories of non-skeletal
and flexible activities. Under the daily time budget and non-negativity of participation rate constraints, the models predict
optimal sets of frequencies of the activities under consideration (given the average duration of each activity type). The
daily time budget considers at-home basic needs and night sleep activities together as a composite activity. The concept of
composite activity ensures the dynamics and continuity of time allocation and activity/travel behaviour by encapsulating altogether
the activity types that are not of our direct interest in travel demand modelling. Workers’ total working hours (skeletal
activity and not a part of the non-skeletal activity time budget) are considered as a variable in the models to accommodate
the scheduling effects inside the generation model of non-skeletal activities. Incorporation of previous day’s total executed
activities as variables introduces day-to-day dynamics into the activity program generation models. The possibility of zero
frequency of any specific activity under consideration is ensured by the Kuhn-Tucker optimality conditions used for formulating
the model structure. Models use the concept of random utility maximization approach to derive activity program set. Estimations
of the empirical models are done using the 2002–2003 CHASE survey data set collected in Toronto.
相似文献
Eric J. MillerEmail: |
543.
A. Harifi A. Aghagolzadeh G. Alizadeh M. Sadeghi 《Transportation Research Part C: Emerging Technologies》2008,16(6):731-741
Antilock brake system (ABS) has been designed to achieve maximum negative acceleration by preventing the wheels from locking. Research shows that the friction between road and tire is a nonlinear function of wheel slip. Therefore, maximum negative acceleration can be achieved by designing a suitable control system for wheel slip regulation at its optimum value. Since there is a lot of nonlinearity and uncertainty (uncertainty in mass and center of gravity of the vehicle and road condition) in vehicle dynamics, a robust control method should be used. In this research, a sliding mode controller for wheel slip control has been designed based on a two-axle vehicle model. Important considered parameters for vehicle dynamic include two separated brake torques for front and rear wheels as well as longitudinal weight transfer caused by the acceleration or deceleration. One of the common problems in sliding mode control is chattering phenomenon. In this paper, primary controller design has been improved using integral switching surface to reduce chattering effects. Simulation results show the success of integral switching surface in elimination of chattering side effects and by high performance of this controller. At the end, the performance of the designed controller has been compared with three of the prevalent papers results to determine the performance of sliding mode control integrated with integral switching surface. 相似文献
544.
Transportation infrastructure planning process requires cost–benefit analysis in the evaluation of project proposals. Value of time (VOT) facilitates the conversion of travel time savings, which is a significant proportion of benefits in monetary terms. In cases where VOT has not been established, planners resort to crude estimates that often results in erroneous or biased measurements of benefits. This is the case of the Western Visayas region in the Philippines where transportation studies are rare. Secondary cities and its peripheral regions have often been overlooked subjects of transportation studies. In this study, multinomial logit models using revealed preference data were estimated to facilitate the calculation of the VOT. The total cost, square of the total cost, and total time were identified as significant explanatory variables affecting mode choice. The square of the total cost term was introduced in the models in order to account for income effect. Results indicate that VOT estimates for the inter-island passenger transportation between Iloilo and Negros Occidental generally range from 78.15PHP to 179.15PHP (1.91USD to 4.37USD) depending on trip and traveller characteristics. 相似文献
545.
Simon?P.?BlaineyEmail author John?Armstrong Andrew?S.?J.?Smith John?M.?Preston 《Transportation》2016,43(3):425-442
This paper describes an integrated methodology for identifying potential ‘quick wins’ for mode shift from road to passenger rail transport. Firstly, a procedure for analysing rail’s relative competitiveness in the market for passenger transport between large urban areas is developed and then applied to a UK case study. The purpose of such analysis is to allow the identification of flows where rail is currently relatively uncompetitive (in terms of journey time in particular) and to assess the reasons for this poor performance, so that the issues which suppress rail use may be addressed. In parallel, a framework, methodology and tool for the assessment of existing and potential capacity (trains, seats, TEUs, etc.) is developed for both passenger and freight traffic, to identify and address network constraints. An illustrative example of the use of these demand and capacity assessment tools is then presented, with the tools used to identify and evaluate flows where rail demand is suppressed by poor service quality and where spare capacity exists which would allow the passenger rail service to be improved without requiring significant investments in infrastructure. The effects of such improvements on demand are predicted, and the cost implications of operating such additional services are discussed. The analysis suggests that there may be significant potential for increasing rail’s mode share by providing additional inter-urban services where rail currently offers an inferior service. 相似文献
546.
Estimation of train dwell time at short stops based on track occupation event data: A study at a Dutch railway station
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Train dwell time is one of the most unpredictable components of railway operations, mainly because of the varying volumes of alighting and boarding passengers. However, for reliable estimations of train running times and route conflicts on main lines, it is necessary to obtain accurate estimations of dwell times at the intermediate stops on the main line, the so‐called short stops. This is a great challenge for a more reliable, efficient and robust train operation. Previous research has shown that the dwell time is highly dependent on the number of boarding and alighting passengers. However, these numbers are usually not available in real time. This paper discusses the possibility of a dwell time estimation model at short stops without passenger demand information by means of a statistical analysis of track occupation data from the Netherlands. The analysis showed that the dwell times are best estimated for peak and off‐peak hours separately. The peak‐hour dwell times are estimated using a linear regression model of train length, dwell times at previous stops and dwell times of the preceding trains. The off‐peak‐hour dwell times are estimated using a non‐parametric regression model, in particular, the k‐nearest neighbor model. There are two major advantages of the proposed estimation models. First, the models do not need passenger flow data, which is usually impossible to obtain in real time in practice. Second, detailed parameters of rolling stock configuration and platform layout are not required, which makes the model more generic and eases implementation. A case study at Dutch railway stations shows that the estimation accuracy is 85.8%–88.5% during peak hours and 80.1% during off‐peak hours, which is relatively high. We conclude that the estimation of dwell times at short stop stations without passenger data is possible. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
547.
In order to prevent the uncontrolled release of seatbelt buckles due to high acceleration caused by pretensioners, anti-g
buckles that have pendulum-shaped g-masses to block the releasing motion are commonly adopted in seatbelt systems. However,
even with the wide applications of anti-g buckles, the underlying operational principles of anti-g buckles have yet to be
investigated. This work studies conditions for the engagement of the g-mass to prevent inertial release, and conditions for
maintaining a blocked state under very high acceleration. Using a multibody model of an anti-g buckle, the effects of various
design parameters on the performance of the anti-g buckle have been examined. It turns out that design variables associated
with the geometry of the g-mass and its contacting surface configuration play important roles. In order to account for the
dynamic interaction between driver and seatbelt, a multibody model of a seatbelt system is combined with a dummy model to
form a single dynamic system. Using the measured displacement of the buckle during the explosion of a pretensioner as the
driving condition for simulation, dynamic analysis of the seatbelt with driver interaction has been carried out. Through comparison
with measured and computed accelerations of webbing, which shows good agreement, the validity of the model has been demonstrated.
The dynamic model for seatbelt and driver can be used as a design tool for the development of anti-g buckles. 相似文献
548.
A. Broatch J. M. Luján S. Ruiz P. Olmeda 《International Journal of Automotive Technology》2008,9(2):129-140
Most of hydrocarbon (HC) and carbon monoxide (CO) emissions from automotive DI Diesel engines are produced during the engine
warm-up period and are primarily caused by difficulties in obtaining stable and efficient combustion under these conditions.
Furthermore, the contribution of engine starting to these emissions is not negligible; since this operating condition is highly
unfavorable for the combustion progress. Additionally, the catalytic converter is ineffective due to the low engine temperature.
In conjunction with adequate engine settings (fuel injection and fresh air control), either the glow plugs or the intake air
heater are activated during a portion of the engine warm-up period, so that a nominal engine temperatures is reached faster,
and the impact of these difficulties is minimized. Measurement of gaseous pollutants during engine warm-up is currently possible
with detectors used in standard exhaust gas analyzers (EGA), which have response times well-suited for sampling at such transient
conditions. However, these devices are not suitable for the measurement of exhaust emissions produced during extremely short
time intervals, such as engine starting. Herein, we present a methodology for the measurement of the cumulative pollutant
emissions during the starting phase of passenger car DI Diesel engines, with the goal of overcoming this limitation by taking
advantage of standard detectors. In the proposed method, a warm canister is filled with an exhaust gas sample at constant
volumetric flow, during a time period that depends on the engine starting time; the gas concentration in the canister is later
evaluated with a standard EGA. When compared with direct pollutant measurements performed with a state-of-art EGA, the proposed
procedure was found to be more sensitive to combustion changes and provided more reliable data. 相似文献
549.
550.
The forward collision warning system, which warns danger to the driver after sensing possibility of crash in advance, has been actively studied recently. Such systems developed until now give a warning, regardless of driver’s driving propensity. However, it’s not reasonable to give a warning to every driver at the same time because drivers are different in driving propensity. In this study, to give a warning to each driver differently, three metrics classifying driver’s driving propensity were developed by using the driving data on a testing ground. These three metrics are the predicted time headway, required deceleration divided by the deceleration of the leading vehicle, and the resultant acceleration divided by the deceleration of the leading vehicle. Driving propensity was divided into 3 groups by using these metrics for braking and steering cases. In addition, these metrics were verified by making sure that braking propensity could be classified on public roads as well. 相似文献