Cars In Cities Research Articles

CFD model simulation of dispersion from chlorine railcar releases in industrial and urban areas

To assist in emergency response decisions and planning in case of releases of pressurized liquefied chlorine from railroad tank cars in industrial sites and cities, the FLACS Computational Fluid Dynamics (CFD) model has been used to simulate the transport and dispersion of the dense chlorine cloud. Two accident locations are studied: an actual railcar accident at an industrial site in Festus, MO, and a hypothetical railcar accident at a rail junction in the Chicago urban area. The results show that transport of a large dense gas release at ground level in an industrial site or large city could initially extend a hundred meters or more in the upwind and crosswind directions. The dense cloud may follow terrain drainage, such as river channels. Near the source, the obstacles tend to slow down the dense gas cloud and may constrain it and cause increased concentrations. Farther downwind, the obstacles may cause enhanced mixing and dilution once the cloud has grown larger. In some cases, significant amounts of cloud mass may become “trapped” in obstacle wakes for many minutes after the main cloud has passed. Although the CFD model can account for the details of the flow and dispersion much better than standard widely-used simple dense gas models, many similarities are found among the various models in their simulated variations with downwind distance of the maximum cloud centerline concentration.

On the Simulation of Traffic Signals Operation

Traffic lights are available in almost all cities and towns worldwide. They solve many traffic congestion problems, save numerous human lives and avoid frequent automobile accidents. Optimizing the operation of traffic light systems in roads is essential for any city's economy, safety and environment. Simulation technology is probably the best tool to analyze and optimize the operation and design of traffic light systems. The increasing use of automobiles in cities has lead city administrators and local governments to install traffic lights and detectors in large quantities in order to avoid accidents and optimize the movement of automobiles and humans. Although signalization can solve traffic conflicts at the intersections, it causes stoppage. The chief objective of optimal traffic control is to improve system mobility and throughput at reduced delays. Delays and stops are not only irritating and pricey to drivers and passengers, but they also add to air contamination and energy use. In this paper, we analyze and demonstrate how the timings of a traffic light system are calculated in order to determine the optimum and proper timings needed to optimize traffic flow.

Showcase and showroom: automobiles and experience architecture

In the postmodern society, 'emotions' are of growing importance in the constitution of meaning in everyday life. Emotion, the pivot of a new 'experience rationality' (Schulze, 1992), lubricates the 'experience economy' (Pine and Gilmore, 1999). Architects claim their part in the emotional branding of cars ? designing local showrooms, as well as great showcases for the brands at the headquarters of automobile companies. Nowadays, consumers consider car shopping an outing: showrooms along auto boulevards, 'car cities', and great automobile shows offer an opportunity. This paper analyses the relationship between auto-loyalty, brand loyalty and showroom architecture. Does the brand-architecture nexus shape postmodern consumer identity? Can showroom architecture produce brand loyalty, something both companies and architects claim? To answer these questions, we interviewed German company officials and their architects, Gunter Henn (Munich), Qua (Amsterdam) and Van Berkel (UN Studio Amsterdam). We also visited showrooms in the Netherlands and interviewed the dealers. Theoretical research fed our argued interpretation of these data and produced a hypothesis.

Progress and future challenges in controlling automotive exhaust gas emissions

By the early 1970s increased use of cars in some major cities had resulted in serious concerns about urban air quality caused by engine exhaust gas emissions themselves, and by the more harmful species derived from them via photochemical reactions. The three main exhaust gas pollutants are hydrocarbons (including partially oxidised organic compounds), carbon monoxide and nitrogen oxides. Engine modifications alone were not sufficient to control them, and catalytic systems were introduced to do this. This catalytic chemistry involves activation of small pollutant molecules that is achieved particularly effectively over platinum group metal catalysts. Catalytic emissions control was introduced first in the form of platinum-based oxidation catalysts that lowered hydrocarbon and carbon monoxide emissions. Reduction of nitrogen oxides to nitrogen was initially done over a platinum/rhodium catalyst prior to oxidation, and subsequently simultaneous conversion of all three pollutants over a single three-way catalyst to harmless products became possible when the composition of the exhaust gas could be maintained close to the stoichiometric point. Today modern cars with three-way catalysts can achieve almost complete removal of all three exhaust pollutants over the life of the vehicle. There is now a high level of interest, especially in Europe, in improved fuel-efficient vehicles with reduced carbon dioxide emissions, and “lean-burn” engines, particularly diesels that can provide better fuel economy. Here oxidation of hydrocarbons and carbon monoxide is fairly straightforward, but direct reduction of NOx under lean conditions is practically impossible. Two very different approaches are being developed for lean-NOx control; these are NOx-trapping with periodic reductive regeneration, and selective catalytic reduction (SCR) with ammonia or hydrocarbon. Good progress has been made in developing these technologies and they are gradually being introduced into production. Because of the nature of the diesel engine combustion process they produce more particulate matter (PM) or soot than gasoline engines, and this gives rise to health concerns. The exhaust temperature of heavy-duty diesels is high enough (250–400°C) for nitric oxide to be converted to nitrogen dioxide over an upstream platinum catalyst, and this smoothly oxidises retained soot in the filter. The exhaust temperature of passenger car diesels is too low for this to take place all the time, so trapped soot is periodically burnt in oxygen above 550°C. Here a platinum catalyst is used to oxidise higher than normal amounts of hydrocarbon and carbon monoxide upstream of the filter to give sufficient temperature for soot combustion to take place with oxygen. Diesel PM control is discussed in terms of a range of vehicle applications, including very recent results from actual on-road measurements involving a mobile laboratory, and the technical challenges associated with developing ultra-clean diesel-powered cars are discussed.

Évaluation des potentiels de réduction des trafics automobiles dans le cas de la zone dense francilienne

The Pari 21 research project does not attempt to justify a move towards a radically different system—practically everything there is to say about the benefits and disadvantages of cars in cities has already been said. Instead, the project will perform simulations and assess, from the point of view of individuals, the feasibility of a transport system that is based mainly On the use of modes Other than the private car in the densely populated zone Of the Greater Paris Area (Paris city plus the inner suburbs). By constructing and evaluating transport policy scenarios, this research also aims to measure the potential for reducing car use in highly urbanized zones, particularly that which results from the reduction in journey speeds which are a likely consequence of the policies in question The method is based on repeated iterations of a simulation model which combines the assignment of round trips to modes other than the automobile with reformulations of transport supply. Demand is channelled towards personal modes (walking, cycling), public transport and a combination of personal and public modes. These iterations are based on the 1991-1992 Paris Region comprehensive travel survey which recorded all the round trips by car made in a typical day by the individuals living in the zone (i.e. the sequence of all trips made between each time the individual leaves home and returns home).

Transportation for livable cities

Transportation for Livable Cities, Vukan R. Vuchic, New Jersey, Center for Urban Policy Research, Rutgers University, 1999, 352 pp., US$29.95The debate over the role of public transit and the role of automobiles in cities has energised planners for many decades. Authors who take on this controversy usually hold strong positions at one end or the other of the spectrum of policy choices. Vukan R. Vuchic, UPS Foundation Professor of Transportation at the University of Pennsylvania, is no exception. In his comprehensive book, Transportation for Livable Cities, he explains the importance of offering true choices in transportation which are appropriate to the size and complexity of an urban region. His goal is to explain the case for more transit, for regionally integrated multi-modal transportation, and for learning from European experience. The basic approach of the book is to enumerate critical decisions about transportation in urban areas-how many expressways to build, whether they go downtown, whether to introduce rail transit and what type, and how to coordinate and fund the transportation system. Vuchic has tried to incorporate all of the experiences and findings of his career into advice on how to tackle these problems. His goal is to improve transportation planning for cities in countries like the USA and the UK where automobile domination is strong. He uses the USA as his primary object of study and recommendations.As Vuchic notes, the USA has often been innovative in urban transportation-having used and developed streetcars and associated ?suburbs', having used passenger railroads to tie exurban towns and villages to the metropolis, and having done key early work in highway and road safety. But since the Second World War the USA has made many wrong turns according to the author. In short, the massive Federal support for the Interstate Highway System made automobile dependency and dominance inevitable. Since it became clear around 1970 that the pendulum had swung too far towards the automobile, there have been halting attempts to support public transit and encourage more environmentally sustainable transportation. But as he notes (p. 16) c... the present differences between the United States and its peers in urban transportation are not as extreme in laws and officially proclaimed policies as they are in implementation'.Vuchic clearly states the case for more transit, and for more coordinated multi-modal transportation systems. He does not really conduct a debate, however. In most cases the proponents of his approach are given due attention, but the opposition is not given much due. For example, he cites the transit side of the auto versus transit debate (Newman and Ken worthy, 1989), but not the auto side (Gordon and Richardson, 1989). This debate has changed over the years into a broader discussion of sprawl which is very important to the transportation choices in urban regions (Gordon and Richardson, 1997; Ewing, 1997). Unfortunately, Vuchic does not make the case as well as he could because he does not take on auto advocates directly.Again he misses an opportunity to take on transit critics directly when he dismisses routine errors; the mistakes made in many cities in the construction of new subways and light rail systems. Detailed critiques of these projects (Pickrell, 1992) are not mentioned nor effectively countered.A key chapter in the heart of the book is his review of what has been done in peer countries (and their cities). His discussion of national policy in Germany, France, The Netherlands, Great Britain, Switzerland, Norway, Sweden and Finland is clearly organised and includes details on 12 cities. …

The Fifth Branch: Science Advisors as Policymakers

We learned in our civics classes that federal government has three branches: executive, legislative, and judicial. In practice, observers of governmental process have long recognized importance of a fourth branch—the regulatory agencies such as Environmental Protection Agency (EPA) and Food and Drug Administration (FDA), which have much to do with interpreting laws, writing regulations, and enforcing them. The proliferation of science and technology and resulting products and services have led these agencies to seek expert, scientific advice concerning health, safety, and environmental policy. Sheila Jasanoff views scientific advisory process as so pervasive and influential that she has labeled it the fifth branch. These scientific advisers play central roles in determining whether we should eat supermarket apples, use hair spray, drive cars in inner cities, incinerate our wastes, generate nuclear energy, [or] release genetically engineered organisms into environment (p v). Despite this influence,

Analysis of Running Pattern and Fuel Economy of Cars in Cities

For a long range prospect of energy demands, improvement of fuel economy(FE) of cars is an important factor because it is not easy to substitute gasoline demands by other energy resources. Although recent FE for a standard running pattern has been remarkably improved, FE in real use depends on actual running patterns in cities, and there are some discrepancies between actual and the standard FE. Therefore, to improve accuracy of energy demands prediction, quantitative analysis of running patterns and their effects on FE is required, and authors measured actual running profiles for various road conditions by developing a simple measurement system, from which basic running patterns in cities are obtained. Then a model to estimate FE from the data is developed, and effects of present city running on FE are analysed quantitatively with the model, which can be used to evaluate future changes of FE in real use.