Evaluating bus accident risks in public transport

Public transit buses may be considered a safer transportation mode as opposed to others (e.g., private cars). However, safety is a crucial issue regarding transit buses from the perspectives of operators and passengers due to the relevant implications it generates. Therefore, evaluating the accident risk on bus routes provides an opportunity to improve the safety performance of transit operators. Previous research identified patterns of bus accidents and shed light on understanding the effects of many factors regarding frequency and severity of bus accidents. However, no studies have investigated accident risks in bus transit, while considering frequency, severity and exposure factors in a single function. This paper proposes a new methodology for evaluating the accident risk for each transit bus route. At first, the methodology identifies the risk components in terms of frequency, severity and exposure factors that may affect bus accidents. Next, it integrates these terms, to build a risk bus accident function providing a ranking of safety performance for each route. The feasibility of this methodology is demonstrated in a real case study using 3,457 bus accidents provided by a mid-sized Italian bus operator. This experiment shows that transit managers could adopt this methodology to perform an accurate safety analysis on each route. Moreover, this methodology may be implemented in a road traffic safety management system for bus transit operators interested in the monitoring of safety performance, in the evaluation of the risk of accidents on routes, and in the certification process according to recent safety norms

Performance and reliability comparison of 1T-1R RRAM arrays with amorphous and polycrystalline HfO2

In this work, a comparison between 1T-1R RRAM 4kbits arrays manufactured either with amorphous or polycrystalline HfO2 in terms of performance, reliability, Set/Reset operations energy requirements, intra-cell and inter-cell variability during 10k Set/Reset cycles is reported. Polycrystalline array shows higher current ratio, lower switching voltages, lower power consumption, minor endurance degradation and higher overall yield than amorphous array. The drawbacks are represented by the higher Forming voltage, the larger read current distribution after Forming and the higher Reset voltage dispersion

RRAM Reliability/Performance Characterization through Array Architectures Investigations

The reliability and performance characterization of each non-volatile memory technology requires the thorough investigation of dedicated array test structures that mimic the real operations of a fully functional integrated product. This makes no exception also for emerging non-volatile memories like the Resistive Random Access Memory (RRAM) concept. An extensive electrical characterization activity performed on test vehicles manufactured in a CMOS backend-of-line process allowed the first glance estimation of operation modes and reliability threats typical of this technology. In this paper, it is provided a review of the most important issues like forming instabilities, optimal set/reset operation finding, and read disturb to provide a guideline either for a further technology optimization or an efficient algorithms co-design to handle these reliability/performance threats

A profitability comparison between a “one-way” car sharing service and a "modified one-way" car sharing service

The research looks at comparing the different performance offered by two types of one-way car sharing services. In particular, we compare the “traditional” service in which users can return vehicles to a pre-determined permitted parking space to the “modified” service in which the decision of where to return the vehicle to is made at the end of its usage and vehicles can be returned also outside the permitted parking areas. The comparison is based on common and given demand/offer assumptions. The mathematical modelling uses state of the art algorithms that allow us to determine for both types of service the optimal number of personnel to re-position the vehicles in order to maximise profit. In particular, the attractiveness of the two services herewith compared, has been analysed both in terms of overall profitability as well as in terms of maximum number of users. The results show and quantify how the “modified” service, whilst allowing a greater degree of flexibility to users in terms of return locations, causes lower economic returns for the service company and lowers the number of users that can be served. Finally, the model allows us to calculate the required tariff increase necessary to transform a “traditional” service into a “modified” service assuming an inelastic demand curve as well as constant profits for the service company

Standing Passenger Comfort: A New Scale for Evaluating the Real-Time Driving Style of Bus Transit Services

On-board bus comfort is a key factor affecting the quality of transit service. Thus, its assessment is crucial for public transport companies, as it can support the monitoring, evaluation and implementation of specific actions to improve their services. Previous research mainly focused on separate subjective and objective measurements of on-board comfort. Furthermore, even if concurrent measurements of objective and subjective on-board comfort have been collected, no study has built a gradual scale for the real-time measurement of comfort. This paper covers this gap by integrating subjective measurements of driving style with objective measurements of longitudinal and transversal accelerations collected by intelligent transportation system tools. These findings are very useful because they represent the first contribution for establishing a comfort scale in a real operational environment as a tool to regulate driver behavior, i.e., each driver will be able to recognize when passengers experience conditions of discomfort and acts to improve comfort

Reliability and Cell-to-Cell Variability of TAS-MRAM arrays under cycling conditions

The impact of 500k write cycles on 1kbits TASMRAM arrays has been evaluated by extracting a set of characteristic parameters describing the technology in terms of cell-to cell variability and switching reliability. The relationship between switching voltages and cell resistances has been investigated in order to define the most reliable working conditions

Introducing a relocation service for one-way carsharing with a first-in first-served policy

In one-way carsharing users are allowed to return cars to locations different from those where they were picked up. but directional imbalances in their requests result in the accumulation of unnecessary cars in some areas, whereas other areas face car shortages. To correct tins situation, we investigate the introduction of a new relocation service by a staff equipped with foldable motorcycles: They are driven to move to unused cars and are put inside cars, which are driven by the staff where they are requested. Although the relocation staff size can be determined by a state-of-The-Art model, it tends to overestimate the manpower maximizing the overall system profitability in a first-in first served policy. Tins paper presents an optimization model correcting this drawback. Tins model can be used to investigate how different manpower levels change the percentage of satisfied user bookings and determine the most profitable staff size configuration

Increased material differentiation through multi-contrast x-ray imaging: a preliminary evaluation of potential applications to the detection of threat materials

Most material discrimination in security inspections is based on dual-energy x-ray imaging, which enables the determination of a material's effective atomic number (Z eff) as well as electron density and its consequent classification as organic or inorganic. Recently phase-based "dark-field" x-ray imaging approaches have emerged that are sensitive to complementary features of a material, namely its unresolved microstructure. It can therefore be speculated that their inclusion in the security-based imaging could enhance material discrimination, for example of materials with similar electron densities and Z eff but different microstructures. In this paper, we present a preliminary evaluation of the advantages that such a combination could bear. Utilising an energy-resolved detector for a phase-based dark-field technique provides dual-energy attenuation and dark-field images simultaneously. In addition, since we use a method based on attenuating x-ray masks to generate the dark-field images, a fifth (attenuation) image at a much higher photon energy is obtained by exploiting the x-rays transmitted through the highly absorbing mask septa. In a first test, a threat material is imaged against a non-threat one, and we show how their discrimination based on maximising their relative contrast through linear combinations of two and five imaging channels leads to an improvement in the latter case. We then present a second example to show how the method can be extended to discrimination against more than one non-threat material, obtaining similar results. Albeit admittedly preliminary, these results indicate that significant margins of improvement in material discrimination are available by including additional x-ray contrasts in the scanning process

Assessing the Risk of Bus Crashes in Transit Systems

Although public transport buses may be considered a safe transportation mode, bus safety is a crucial issue from the perspectives of operators, passengers and local authorities owing to the relevant implications it generates. Therefore, assessing the risk of crashes on bus routes may help improve the safety performance of transit operators. Much research has identified patterns of bus crashes to understand the effects of many factors on the frequency and the severity of them. Conversely, to the best of our knowledge, the research measuring the risk of crashes in bus transit networks is seldom faced. This paper adjusts existing methods to assess the safety on bus transit networks by the integration of safety factors, prediction models and risk methods. More recisely, first, the methodology identifies several safety factors as well as the exposure risk factors. Second, this methodology specifies the risk components in terms of frequency, severity and exposure factors that may affect bus crashes and models their relationships in a risk function. Third, this methodology computes the risk of crashes for each route and provides a ranking of safety performance. A real case study demonstrates the feasibility of this methodology using 3,457 bus crashes provided by a mid-sized Italian bus operator. This experiment shows that transit managers could adopt this methodology to perform an accurate safety analysis on each route. Moreover, this methodology could be implemented in a road traffic safety management system in order to evaluate the risk of crashes on routes, monitor the safety performance of each route and qualify each route according to recent safety norms