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[en] In his famous novel The Caves of Steel, Isaac Asimov imagined a public transportation system based on a series of parallel moving walkways accelerating pedestrians progressively toward a high-speed central lane which continuously carries the crowds of the gigantic cities of our future Earth. In this paper, it is shown that the user of this system would face an interesting optimization problem, namely the design of the path which would minimize the travel time from one place to another. This problem is solved with the classical techniques of Lagrangian mechanics. (paper)
[en] The concept of smart city gives an excellent resolution to construct and develop modern cities, and also demands infrastructure construction. How to build a safe, stable, and highly efficient public transportation system becomes an important topic in the process of city construction. In this work, we study the structural and robustness properties of transportation networks and their sub-networks. We introduce a complementary network model to study the relevance and complementarity between bus network and subway network. Our numerical results show that the mutual supplement of networks can improve the network robustness. This conclusion provides a theoretical basis for the construction of public traffic networks, and it also supports reasonable operation of managing smart cities. (rapid communication)
[en] Arguments for and against the highly controversial levy approved by Translink, the transportation authority in Greater Vancouver, are discussed. This highly controversial plan will cost car owners in the Greater Vancouver Regional District up to $120 per year for transportation improvements to roads, public transit and bicycle paths. Supporters of the levy contend that divisive as the levy may be, it is a bold first step towards a user-pay system. The GVRD transportation system is badly in need of improvement and the levy is a quick and temporary way to finance the necessary work. However, even supporters of the scheme suggest that the levy should not be seen as the final solution. Instead, they urge Translink to move towards a usage-pay system, including a fuel tax, combined with road and bridge tolls. A pay-as-you-go system would encourage residents to drive less, or to drive more fuel-efficient vehicles. Regardless of how the public reacts to the levy system, Translink should commit to building a more equitable system to pay for the transportation improvements needed by the region
[en] Following a feasibility study and a detailed specification phase, the realization of a fuel cell city bus prototype was started in autumn 1996. The project is a joint development effort of Siemens, MAN and Linde, which receives a 50 % funding by the Bavarian State Ministry for Economic Affairs, Transport and Technology (BStMWVT) in the context of the Hydrogen Initiative Bavaria. An MAN low-floor bus will be equipped with the components for a fuel cell drive system. The PEM fuel cell is developed by the power generation division of Siemens. Four fuel cell modules deliver a total electrical output of 120 kW to the two electric motors, which are linked by a summation gearbox by the Siemens Transportation Systems Division. MAN Technologie AG is responsible for the compressed hydrogen storage system allowing for a driving range of more than 250 km, while Linde AG takes care of the hydrogen periphery and delivers the hydrogen for the test operation scheduled for the beginning of the year 2000. Project coordination is done by Ludwig-Boelkow System-technik GmbH. The project is divided into four phases. The conceptual design phase is scheduled to last until the end of 1997. The partly overlapping system integration phase will end in the first quarter of 1999. The subsequent test and commissioning phase will prepare the test operation at the beginning of 2000 with a bus operator yet to be defined. (author)
[en] Rapid economic growth has caused severe traffic congestion and air pollution in the Seoul metropolitan area (SMA). As a consequence, traffic demand management (TDM) policies have been implemented to mitigate traffic congestion in the region. This study analyzed travel patterns that occurred as a result of transport policy changes in Seoul between 1996 and 2002. General travel pattern changes in the SMA were compared with the travel patterns of regions with car-oriented road construction policies and public transit-invested regions. Results of the study showed that investment in road construction had no significant impact on reducing traffic congestion. The modal shift to public transit modes caused a reduction in the number of cars on roads. The study demonstrated that transit-oriented policies can be used to overcome severe traffic congestion. 7 refs., 7 tabs., 6 figs.
[en] The question of whether the stellar populations in the Milky Way take part in the flaring of scale heights as observed for the H I gas is a matter of debate. Standard mass models for the Milky Way assume a constant scale height for each of the different stellar distributions. However, there is mounting evidence that at least some of the stellar distributions reach, at large galactocentric distances, high altitudes, which are incompatible with a constant scale height. We discuss recent observational evidence for stellar flaring and compare it with H I data from the Leiden/Argentine/Bonn survey. Within the systemic and statistical uncertainties we find a good agreement between both.
[en] Given the difference between peak and off-peak occupancy rates in public transport, emissions per traveller kilometre are lower in the peak than in the off-peak period, whereas the opposite pattern is observed for cars. It is argued that it is much more fruitful to analyse environmental effects in marginal terms. This calls for a careful analysis of capacity management policies of public transport suppliers that are facing increased demand during both peak and off-peak periods. A detailed analysis of capacity management by the Netherlands Railways (NS) revealed that off-peak capacity supply is mainly dictated by the demand levels during the peak period. The analysis included the effects of increased frequency and increased vehicle size on environmental impacts, while environmental economies of vehicle size were also taken into account. The main conclusion is that the marginal environmental burden during the peak hours is much higher than is usually thought, whereas it is almost zero during the off-peak period. This implies a pattern that is the precise opposite of the average environmental burden. Thus, an analysis of environmental effects of public transport based on average performance would yield misleading conclusions
[nl]Aangezien de bezettingsgraad van het openbaar vervoer in de spits hoger ligt dan daarbuiten zou men verwachten dat spitsreizigers minder vervuilen dan dalreizigers. In deze bijdrage wordt aangetoond dat dit in elk geval voor de trein niet opgaat. De reden hiervan is dat een extra treinreiziger in de spits leidt tot de inzet van extra capaciteit (meer of langere treinen) die ook buiten de spits wordt ingezet. Dit betekent dat een extra treinreiziger buiten de spits niet leidt tot de inzet van meer capaciteit: er is dan immers ruimte genoeg in de treinen. De marginale milieukosten van treinreizigers buiten de spits liggen dus dicht bij nul. Voor deze analyse is het onderscheid tussen gerniddelde en marginaie kosten essentieel. Een ander belangrijk concept waarmee in de analyse rekening wordt gehouden betreft het bestaan van milieu-schaalvoordelen: per zitplaats vervuilen kleine voertuigen meer dan grote. De conclusie is dat NS in overweging zou moeten nemen om capaciteitsplanning en prijszetting in sterkere mate af te stemmen op de vraag. Dit is niet alleen goed voor het milieu maar zou ook gunstige bedrijfseconomische effecten kunnen hebben
[en] This article described different traffic congestion schemes that cities around the world have adopted to ease traffic grid-lock. Congestion fees that discourage road use involve assigning a price to a road based on the demand for using that road. A weekday congestion fee which was imposed on drivers in the city of London in 2003 resulted in a 30 per cent drop in vehicular traffic in the city centre. The pricing structure was independent of vehicle type, distance travelled or time of day. The successful scheme is credited with an increase in cycling and public transit ridership as well as a decrease in accidents and air pollution without hindering business within the congestion zone. However, the effectiveness of congestion fees in North America is questionable. Although San Diego's high-occupancy toll lanes have helped reduce congestion and pollution because the revenue raised is invested in public transportation, objections have been raised regarding plans to implement congestion fees in San Francisco and New York city centres because doing so would prevent those with low incomes from driving in the city. London has responded to such challenges by putting all net revenues derived from the fees back into public transportation. Similar measures were taken in Stockholm, Sweden where massive improvements were made to its transit system prior to introducing congestion fees to avert criticism. In order for congestion fees to be effective and gain public approval, there should be clear objectives that include demand management, good transportation alternatives, revenues that go to public transit and a simple pricing system that uses proven technology. The cumulative annual cost of congestion in 9 urban centres in Canada ranged from $2.3 billion to $3.7 billion in 2002 according to Transport Canada. Analysts have cautioned that congestion schemes would be difficult to duplicate in North American cities that are highly dependent on automobiles. However, the authors emphasized that this should not deter Canadian municipalities from taking action to reduce grid-lock, particularly when there are lessons from which to learn. 2 refs., 1 fig
[en] In most countries with greenhouse gas emission reduction commitments, transportation has been relatively spared, thus, far in the targeting of reduction obligations, owing to the supposedly high marginal cost. With the prospect of tightening reduction targets, pressure is, however, mounting to address transportation more seriously in the near term and not to rely solely on medium to long-term breakthroughs of alternative fuel technologies. This means stricter policies at the demand side of the mobility market. In addition to fiscal and spatial policies, cap-and-trade systems have been put forward as a new option that deserves serious consideration. This paper reviews the possibilities and pitfalls of such a system applied to passenger transport. Key concerns are the transaction costs of the system and trade-offs between transaction cost and equity effects. A simple system with low(er) transaction cost is more likely to invoke politically sensitive equity effects. On the basis of the recent upsurge in monitoring and feedback studies, one may also conclude that the organisation and tailoring of the information interfaces for the household/traveller requires still elaborate study and testing.
[en] Optimal counterflow in centrifuge with typical regime of flow and radially heterogeneous transit flow was found on the basis of refined method for average to radius. Dependences of concentration gradients from parameters of feeding were established in different areas of the flow. It was shown that the radial concentration gradient in the counterflow area approached half its equilibrium value, the axial gradient was small in long rotor under optimum counterflow and end feeding. Taking into account the heterogeneity of transit flow provides reduction in optimal intensity of counterflow and decrease in concentration gradients. Contrary to standard method for average to radius the obtained results are adaptable in the case of arbitrary ratio of feeding and counterflow intensities
[ru]На основе уточненного метода усреднения по радиусу найден оптимальный противоток в центрифуге с типичной схемой течения и радиально неоднородным транзитным потоком. Установлены зависимости градиентов концентрации в различных областях течения от параметров питания. Показано, что в длинном роторе при оптимальном противотоке и конечном питании радиальный градиент концентрации в противоточной области близок к половине своего равновесного значения, осевой градиент мал по сравнению с радиальным. Учет неоднородности транзитного потока приводит к снижению оптимальной интенсивности противотока и уменьшению градиентов концентрации. В отличие от стандартного метода усреднения по радиусу полученные результаты применимы при произвольном соотношении интенсивностей питания и противотока