Direct tire force generation algorithm based on non-iterative nonlinear inverse tire model

The function of vehicle dynamics control system is adjusting the yaw moment, the longitudinal force and lateral force of a vehicle body through several chassis systems, such as brakes, steering and suspension. Individual systems such as ESC, AFS and 4WD can be used to achieve desired performance by controlling actuator variables. However, integrated chassis control systems that have multiple objectives may not simply achieve the desired performance by controlling the actuators directly. Usually those systems determine the required tire forces in an upper level controller and a lower level controller regulates the tire forces through the actuators. The tire force is controlled in a recursive way based on vehicle state measurement, which may not be sufficient for fast response. For immediate force tracking, we introduce a direct tire force generation method that uses a nonlinear inverse tire model, a pseudo-inverse model of vehicle dynamics and the relationship between longitudinal force and brake pressure.     

Cyclist target and test setup for evaluation of cyclist-autonomous emergency braking

From 2018, Autonomous Emergency Braking (AEB) systems dedicated to avoid or mitigate passenger car-tocyclist collisions will be considered in the safety assessment by Euro NCAP. To test such systems, appropriate equipment has been developed in a project called CATS “Cyclist-AEB Testing System”, that has run between April 2014 and August 2016. Moreover, a proposal for the most relevant test scenarios was set up. The objective of the project was to provide proof to Euro NCAP of the relevance of the proposed test scenarios and of the feasibility of practical implementation of the scenarios and test setup. The process regarding the selection, verification and validation of test scenarios is described. The cooperation between 17 industrial partners (car manufacturers and automotive suppliers) in the CATS project has stimulated the harmonization and acceptance of the protocol, target and test setup. The process and intermediate results including the used methodology, have been reviewed by the German Federal Highway Research Institute (BASt) and have been shared on a regular basis during the project with stakeholders in Europe, Japan and the USA. Euro NCAP already indicated to consider the results of the CATS project as the main input to draft the test protocol, including scenarios and target for Cyclist-AEB systems in 2018 and 2020.     

Instantaneous 2-D visualization of spray combustion and flame luminosity of GTL and GTL-biodiesel fuel blend under quiescent ambient conditions

An experimental study has been performed on spray combustion and two-dimensional soot concentration in diesel (ULSD), GTL and GTL-biodiesel fuel jets under high-pressure, high-temperature quiescent conditions. Instantaneous images of the fuel jets were obtained with a high-speed camera. It was confirmed that by blending GTL with 20% rapeseed biodiesel, certain fuel properties such as kinematic viscosity, density, surface tension, volatility, lower heating value and others may be designed and improved to be more like those of conventional diesel fuel but with considerable decrease in the amount of sulfur, PAH, cold filter plugging point, etc. The results showed that the spray tip penetration increased and the spray cone angle decreased when 20% biodiesel fuel was added to GTL fuel. Autoignition of the GTL-biodiesel blend occurred slightly earlier than that of diesel fuel. Experiments under high-pressure, high-temperature conditions showed that higher injection pressure induced a lower soot formation rate. The integrated flame luminosity, which serves as an indicator of soot concentration in the fuel jet, was slightly higher for the GTL-biodiesel blend than for pure GTL fuel due to the slightly higher sulfur content of pure biodiesel fuel.     

Advanced hybrid energy storage system for mild hybrid electric vehicles

Hybrid electric vehicles (HEV) utilize electric power and a mechanical engine for propulsion; therefore, the performance of HEVs is directly influenced by the characteristics of the energy storage system (ESS). The ESS for an HEV generally requires high power performance, long cycle life, reliability and cost effectiveness; thus, a hybrid energy storage system (HESS) that combines different types of storage devices has been considered to fulfill both performance and cost requirements. To improve the operating efficiency and cycle life of a HESS, an advanced dynamic control regime in which pertinent storage devices in the HESS can be selectively operated based on their status is presented. Verification tests were performed to confirm the degree of improvement in energy efficiency. In this paper, an advanced HESS with a battery management system (BMS) that includes an optimal switching control function based on the estimated state of charge (SOC) is presented and verified.     

Children’s mode choice for the school trip: the role of distance and school location in walking to school

Rising levels of childhood obesity in the United States and a 75% decline in the proportion of children walking to school in the past 30 years have focused attention on school travel. This paper uses data from the US Department of Transportation’s 2001 National Household Travel Survey to analyze the factors affecting mode choice for elementary and middle school children. The analysis shows that walk travel time is the most policy-relevant factor affecting the decision to walk to school with an estimated direct elasticity of −0.75. If policymakers want to increase walking rates, these findings suggest that current policies, such as Safe Routes to School, which do not affect the spatial distribution of schools and residences will not be enough to change travel behavior. The final part of the paper uses the mode choice model to test how a land use strategy—community schools—might affect walking to school. The results show that community schools have the potential to increase walking rates but would require large changes from current land use, school, and transportation planning practices.

An analysis on long term emission benefits of a government vehicle fleet replacement plan in northern illinois

There have been a number of studies of the effectiveness of vehicle scrappage programs, which offer incentives to accelerated scrappage of older vehicles often thought to be high emitters. These programs are voluntary and aimed at replacement of household vehicles. In contrast, there is a gap in knowledge related to the emissions benefits of government fleet replacement (retirement) programs. In this study, the efficacy of a fleet replacement program for a local government agency in Northern Illinois, the Forest Preserve of DuPage County (FPDC), is examined using a probabilistic vehicle survival model that accounts for time-varying covariates such as vehicle age and gasoline price. The vehicle lifetime operating emissions are calculated based on the estimated vehicle survival probabilities from the survival model and compared with those derived using the EPA default fleet used in MOBILE6 and the fleet represented by the Oak Ridge National Laboratory (ORNL) survival curve. The results suggest that while there may be short term emission benefits of the FPDC fleet replacement plan, the long-term emission benefits are highly sensitive to economic factors (e.g., future gasoline price) and exhibit a decreasing trend. This indicates that an adaptive multi-stage replacement strategy as opposed to a fixed one is preferable to achieve optimal cost effectiveness.

“I can do perfectly well without a car!”

This article presents the results of a study exploring travellers’ preferences for middle-distance travel using Q-methodology. Respondents rank-ordered 42 opinion statements regarding travel choice and motivations for travel in general and for car and public transport as alternative travel modes. By-person factor analysis revealed four distinct preference segments for middle-distance travel: (1) choice travellers with a preference for public transport, (2) deliberate-choice travellers, (3) choice travellers with car as dominant alternative, and (4) car-dependent travellers. These preference segments differ in terms of the levels of involvement and cognitive effort in travel decision making, the travel consideration-set and underlying motivations. The study showed that for most people there is more to travel than getting from point A to point B, and that there is considerable heterogeneity in middle-distance travel preferences. Policy implications for reducing the need for travel and promoting a modal shift from car to other travel modes are discussed.     

Shift of reference point and implications on behavioral reaction to gains and losses

It is widely recognized that individual decision-making is subject to the evaluation of gains and losses around a reference point. The estimation of discrete choice models increasingly use data from stated choice experiments which are pivoted around a reference alternative. However, to date, the specification of a reference alternative in transport studies has been fixed, whereas it is common to observe individuals adjusting their preferences according to a change in their reference point. This paper focuses on individual reactions, in a freight choice context, to a negative change in the reference alternative values, identifying the behavioural implications in terms of loss aversion and diminishing sensitivity. The results show a significant adjustment in the valuation of gains and losses around a shifted reference alternative. In particular, we find an average increase in loss aversion for cost and time attributes, and a substantial decrease for punctuality. These findings are translated to significant differences in the willingness to pay and willingness to accept measures, providing supporting evidence of respondents’ behavioural reaction.     

Optimal design and benefits of a short turning strategy for a bus corridor

We develop a short turning model using demand information from station to station within a single bus line-single period setting, aimed at increasing the service frequency on the more loaded sections to deal with spatial concentration of demand considering both operators’ and users’ costs. We find analytical expressions for optimal values of the design variables, namely frequencies (inside and outside the short cycle), capacity of vehicles and the position of the short turn limit stations. These expressions are used to analyze the influence of different parameters in the final solution. The design variables and the corresponding cost components for operators and users (waiting and in-vehicle times) are compared against an optimized normal operation scheme (single frequency). Applications on actual transit corridors exhibiting different demand profiles are conducted, calculating the optimal values for the design variables and the resulting benefits for each case. Results show the typical demand configurations that are better served using a short turn strategy.     

Online license plate matching procedures using license-plate recognition machines and new weighted edit distance

License-plate recognition (LPR) technology has been widely applied in many different transportation applications such as enforcement, vehicle monitoring, and access control. Recently, there has been effort to exploit an LPR database for vehicle tracking using popular template matching procedures. Existing template matching procedures assume that the true reference string is always available. However, under a two-point LPR survey, a vehicle could have its plate misread at both locations generating a pair of misread strings (or templates) with no reference for matching. To compensate for LPR misreading problem, we propose a new weight function based on a probability model to match the observed outcomes of a dual LPR setup. Also, considering that reversal errors are never made in LPR machines, new editing constraints as a function of the string lengths are proposed to avoid compensation for reversal errors. These editing constraints are incorporated into the constraint edit distance formulation to improve the performance of the matching procedure. Finally, considering that previous template matching procedures do not take advantage of passage time information available in LPR databases, we present an online tracking procedure that considers the properties of probability distribution of vehicle journey times in order to increase the probability of correct matches. Experimental results show that our proposed procedure can improve the accuracy of LPR systems and achieve up to 97% of positive matches with no false matches. Further research is needed to extend the ideas proposed herein to plate-matching with multiple, i.e., more than two, LPR units.