An investigation of the slipstreams and wakes of trains and the associated effects on trackside people and objects

A mathematical model is developed which predicts if a person or a pushchair is destabilised by a train's slipstream. The model simulates the mean slipstream velocity time history using the theories of potential flow, boundary layer growth and wake decay. The turbulence-induced fluctuations are reproduced with an autoregressive model. A randomised person is generated and subjected to the simulated slipstream, and their response is modelled by a simple solid object and a mass-spring-damper system. If the slipstream forces cause the person to be displaced by a critical distance the person is destabilised. A randomised pushchair is also generated and positioned so as to be capable of being destabilised by either toppling over or moving along the ground on its wheels. A toppling pushchair is modelled as a simple solid object in a similar manner to that of a person, and a pushchair will move along the ground on its wheels if the slipstream force is greater than the frictional force. Greater numbers of destabilised people and pushchairs are associated with the slipstream of a freightliner than that of a passenger train, increasing train speed and decreasing distance from the train side

The influence of resistant force equations and coupling system on long train dynamics simulations

In the simulation of the longitudinal dynamics of long trains, the modeling of the resistant forces and of the coupling system are two essential aspects. The modeling of the resistant forces directly affects the speed reached by each vehicle as well as the in-train forces. A literature review witnesses different laws for the calculation of both ordinary and accidental resistances. One of the objectives of this paper is to evaluate from the numerical point of view the influence of the resistant forces modeling strategy on the simulation outputs, i.e., on the speeds and in-train forces, by comparing different laws for propulsion and curving resistances. For what concerns the connection between the vehicles of the train, it is well known that the connection system is of utmost importance for the safety and running stability of the train. In this paper, the two existing coupling systems, i.e., the European buffer-hook system and the coupler used outside the European continent are first described, both in terms of operation and modelling techniques, and then they are compared on the same simulation scenario. All the simulations are performed on the first scenario of the International benchmark of the longitudinal train dynamic simulators, using the LTDPoliTO code developed by the railway research team from Politecnico di Torino

An investigation into hybrid power trains for vehicles with regenerative braking

Imperial Users onl

Transportation and power solutions for Africa: The assessment and optimization of the Purdue utility platform

The Purdue Utility Platform (PUP) is an off-road utility vehicle that was created to improve agricultural productivity in sub-Saharan Africa by providing appropriate transportation and mobile power solutions. The vehicle design has matured to a level where it now requires more robust engineering tools to perform a rigorous assessment of its function. The assessment will be pursued in two areas: durability of the frame and the roll stability of the vehicle. To assess the durability of the frame, a data acquisition system was installed to collect strain gauge information during the vehicle’s operation. This data was then related to an ANSYS model of the PUP. The investigation of the roll stability of the vehicle was accomplished by building and utilizing a MATLAB simulation showing the vehicle’s dynamics during a turn at relatively high speeds. The results from the frame study showed that the areas under investigation were well under yield stress, but some areas need to be studied further for fatigue failures. Respective loads related to 4 g and 1.6 g accelerations were experienced while operating the vehicle over 4.625” bumps. The roll stability study found that the PUP is primarily safe in rollover, but care must be taken while loading the vehicle. The PUP is least stable when a driver and passenger are sitting in the front seats without a load in the bed. In this case, it is possible that the PUP could roll traveling towards top speed while entering a tight turn on surfaces where the peak friction coefficient is above 0.8. The design tools developed in this assessment can be used in future vehicle designs

How do drivers avoid crashes: the role of driving headway

Rear-end crashes are a major part of road injury burden, accounting for one-third of all vehicle-to-vehicle crashes in New South Wales, Australia. Close following or driving with short headways is a key cause, yet the role of driver behaviour in rear-end crash risk is not well researched. The primary aim of this research was to develop a better understanding of rear-end crashes by assessing headways on Australian roads and investigating driver behaviour and performance associated with close following in crash and non-crash scenarios. Two systematic reviews of headway were conducted. First, a review of research on headway identified the need for a consistent and accurate definition of headway, so the thesis puts forward an improved definition. The second review identified the range of external factors that increase the risk of short headway and increase crash risk including speed, task engagement, lead vehicle type, traffic conditions, road characteristics, weather/visibility, drug use, driving fatigue, innovative lane markings, and various warning systems. These factors were then explored in New South Wales data on rear-end casualty and multiple vehicle crashes. The modelling of these associated factors were confirmed as contributing factors in rear-end crashes, congruent with the review of headway. Higher speed, free flowing traffic, volitional task engagement, low cue environments, and collision warning lead to longer headway. Despite lower fatalities, higher odds of injury were observed for rear-end crashes than other crash types. Rear-end crashes were more likely to lead to multiple vehicle crashes, which had a higher chance of fatality than other types of crashes. Finally, naturalistic driving study data was used to investigate headway during normal driving, exploring close following at different speeds and classifying potential risky driving at various headways. In 64 hrs accumulated across 2101 trips, short headways of under 1 s occurred in around 15% of driving. Common manoeuvres to avoid rear-end crashes when close following were changing lanes, or braking, almost always by the following driver. Headway was associated with both driver speed and posted speed limits, decreasing as posted speed limits increased. Over-the-speed-limit driving was observed in all headway scenarios, but especially in higher speed zones. The findings challenge the notion that rear-end crashes are less severe with low injuries. Road users should be made aware of how frequently safe headways are violated and severity of injury outcomes. Driver education, community engagement, application of driver assistance technology consistent with driver behaviour and safety campaigns need to focus on safer speed and headway management to reduce rear-end crash risk

Analysis and Improvement of Security Concerning Light Commercial Vehicles

Statistics confirm that there is a need to study the safety of vans with a permissible maximum laden mass between 2000 and 3500 kg. as well as develop strategies for improvement. The number of fatalities in accidents involving vans has been constant during the last 10 years, not following the diminishing tendency shown by the general accidents. Not only efficient, but also safer road freight transport is required. This report analyses the security of the light commercial vehicles across the study of the influence from load distribution and the effectiveness of ESC (Electronic Stability Control). Through the medium of simulations made with Pc-Crash software, it has been analysed if the implementation of ESC in vans can at some extent compensate the influence of inaccurate load distributions. Furthermore, due to van’s relatively high centre of gravity and its load, vans may have less avoidance properties than a passenger car. Also (in addition) the differences of braking and dynamic properties between passenger cars and light commercial vehicles have been studied. Neither through literature review nor through own tests, the widespread opinion that vans have much worse active safety systems (brakes, driving stability when negotiating a turn) than passenger cars could not be verified. Effectiveness of ESC implementation was proved just on specific load configurations, highlighting the importance of proper load distribution. On the other hand, Cost-Benefit analysis considering the installation of the ESC shows positive Social benefits for both countries, Denmark and Spain

License to Supervise:Influence of Driving Automation on Driver Licensing

To use highly automated vehicles while a driver remains responsible for safe driving, places new – yet demanding, requirements on the human operator. This is because the automation creates a gap between drivers’ responsibility and the human capabilities to take responsibility, especially for unexpected or time-critical transitions of control. This gap is not being addressed by current practises of driver licensing. Based on literature review, this research collects drivers’ requirements to enable safe transitions in control attuned to human capabilities. This knowledge is intended to help system developers and authorities to identify the requirements on human operators to (re)take responsibility for safe driving after automation

DYNAMIC ANALYSIS OF VEHICLE SYSTEMS Development of a driving simulator Analysis and design of an automatic transmission for motor-scooters

In this work, two researches in the field of dynamic analysis of vehicle systems are presented. The first part of the thesis deals with the development of a driving simulator. This activity was carried out in the framework of a research project co-funded by the Italian Ministry of Education, Universities and Research (MIUR). It aimed at developing a driving simulator for the analysis of the driving style, in order to identify potentially dangerous conditions coming from a non proper interaction between driver, vehicle and environment, especially those related to low driver’s attention. As core part of the driving simulator, a vehicle simulation model, which reproduces the behaviour of the main vehicle systems, was developed. The simulator is made of a fixed driving platform, a single channel visual system and allows to acquire all driver’s inputs and vehicle motion signals. The system was involved in experimental campaigns which allowed the development of the driving style analysis techniques and demonstrated the reliability and the capability of the system. The second part of the thesis treats the dynamic analysis and design of a high efficiency automatic transmission for motor-scooters and was carried out in the framework of the Italian MUSS project funded by the Italian Ministry of Economic Development. Motor-scooters are currently almost always equipped with CVT transmission with rubber belt. This transmission can be very cheap to manufacture, it has good comfort performance but low mechanical efficiency. An alternative automatic transmission was analysed and different architectures were studied. The system is based on a discrete ratio gear box with mechanical control of the gear shit by means of centrifugal clutches and free wheels. A dynamic model of the transmission was developed and its behaviour was investigated by means of results of simulated manoeuvres, highlighting the positive and negative aspects of the system. Finally, a preliminary design was also carried out with reference to an application of the transmission in a hybrid powertrain