The Chatter of Semi-Active On-Off Suspensions and its Cure

Semi-active suspensions are those in which otherwise passively generated damper forces are modulated using feedback control and small amounts of control effort. Recently it was discovered that two-stage, ON-OFF, semi-active control would chatter between the ON and OFF states in a manner similar to bang-bang, active control systems. This chatter is dependent upon the switching algorithm. This paper describes the dynamics of this chatter and suggests alternative control policies for its cure.     

通过停车收费筹措公共服务资金

很多城市的低收入社区面临两大突出难题：超负荷的路内停车和低配置的公共服务。通过构建一项政策可以同时解决这两个难题：基于市场价格征收路内停车费,并将其收入用于本地公共服务运营。基于北京一处胡同改善项目发现,通过合理收取停车费,该社区用于卫生、治安、景观和停车管理的投资能够在不到三年内回收。同时,该项目社区中只有35%的住户拥有私人小汽车,拥车住户的家庭年收入是无车住户的近3倍。     

Public involvement in offshore oil development: Lessons from New England

Abstract

Public perceptions of the risks and benefits of offshore oil development off the New England coast are examined. The influence of these perceptions on state policies toward federal actions is analyzed. A distinct trend of issue identification, critical analysis, consensus building, and state or regional action is observed. Throughout this interactive process between the region and the federal government, even though divergent state positions have evolved, there is a growing regional acceptance of coastal zone management concepts.     

Affordable housing in California's Coastal Zone: A tale of state authority vs. local autonomy

Abstract

This article examines the efforts of the California Coastal Commission to pursue simultaneously goals of environmental quality and affordable housing in the same state‐imposed regulatory program. The authors conclude that the Commission made substantial progress toward realizing both ends. However, the coastal body fell victim to its own successes, and housing was removed from its jurisdiction. As the Coastal Commission exercised its authority, opposition grew in strength and numbers. Key opponents included local government, which lost land‐use regulatory power to the Commission, the building industry, whose relationships with coastal localities were disrupted, and local property owners, whose land was restricted to uses other than the most profitable one.     

寻找路内停车泊位产生的车辆巡游

为寻找路内停车泊位在道路上巡游的车辆是造成交通拥堵的原因之一。首先指出路内停车低价与路外停车高价共同刺激驾驶人选择巡游而非使用路外停车场（库）。其次针对洛杉矶的巡游开展调查,得到车辆平均巡游时耗和距离,并得出每年由此产生的车辆行驶里程、时间浪费、燃油消耗及CO2排放。然后通过分析路内停车价格与车辆巡游的关系,提出城市全日泊位使用率大约为85%时,停车泊位处于供需平衡状态,停车价格较合理。接着以加利福尼亚格雷伍德城停车价格制定及停车收益使用为例,给出停车增量融资的收益回馈方式。最后指出,为了减少拥堵、降低温室气体排放、改善街区环境等,城市应制定合理的路内停车价格并将产生的收益用于改善公共服务。     

Running for the 7:45: The effects of public transit improvements on commuter stress

This research project took advantage of the implementation of a major mass transit improvement by New Jersey Transit which provided a "one-seat ride" into New York City for many commuters who previously had to transfer in Hoboken in order to take Port Authority Trans Hudson (PATH) trains into New York City. The creation of this new service provided a natural experiment in which some riders switched to the new route, while others continued to use their previous route. We studied psychological and psychophysiological responses to these commuting options, using a quasi-experimental, pre-post change, field research design.We found that riders on this new line had lower levels of stress, as multiply measured, than they had earlier, before the advent of this new train, or than did other riders currently using the Hoboken-PATH option. The stress effects seemed to be mediated by the time of the trip – that is, the reduced trip time of the new, direct service seemed to be a primary factor in the reduced stress to riders. Predictability of the trip was also inversely correlated with stress, but did not distinguish between the commuter groups. These results were largely replicated with a student group who rode the same lines acting as simulated commuters.     

Parking subsidies and travel choices: Assessing the evidence

This article reviews empirical studies of how employer-paid parking affects employees' travel choices. A strong effect is found: parking subsidies greatly increase solo driving. When employers reduce or remove parking subsidies, a significant number of solo drivers shift to carpools and/or transit. This conclusion is based on studies of parking subsidies in a variety of circumstances, including central city and suburban areas, private and public employers, and clerical and professional employees. Three measures are developed to compare changes in commute patterns: changes in the share of solo drivers. changes in the number of autos driven to work per 100 employees, and the parking price elasticity of demand for solo driving. The studies reviewed here show that 19 to 81 percent fewer employees drive to work alone when they pay for their own parking. Because 90 percent of American commuters who drive to work receive employer-paid parking, these findings are significant for designing transportation policies to reduce air pollution, traffic congestion, and energy consumption.     

Modelling discretionary travel in the presence of imperfect data

The use of mathematical models in transportation and regional planning is limited by the need to obtain reasonably accurate, complete data sets. In particular complete spatial coverage is required for the usual discrete origin-destination models. Because of the time and cost constraints of obtaining such data, those charged with decision making responsibilities may choose to do without information that could be provided by quantitative models. This paper presents a procedure for estimating origin-constrained flows in situations where complete data collection is difficult or impossible. To this end an abstract model of origin-constrained travel is formulated. The required urban fields are constructed using interpolation and/or approximation techniques applied to available data. The tractability of the general model is demonstrated in the case of estimating the energy consumed in travel to existing or proposed facilities. The ability of the model to function with incomplete data was tested by using it to predict travel to the major retail centers located in the Albany-Schenectady-Troy Metropolitan Area.