Mandating Density: The Blunt Instrument of Smart Growth

This essay expresses concern that urban growth management places too heavy a reliance on densification, particularly upzoning with minimum density requirements in suburban infill situations. Increasing densities may be appropriate when other aspects of urban development can be controlled through urban design. However, evidence provided here indicates that mandating density reduces land consumption, but does not achieve other objectives of growth management, particularly street connectivity, greater use of alternative modes of transportation, and more housing choices. This analysis finds that upzoning and requiring minimum-densities, when used to regulate suburban residential infill developments, is not effective in producing quality compact development. Instead it is resulting in small-lot single-family developments that can only be accessed by cul-de-sac designs augmented by shared driveways. Incentive based approaches to increase density may be preferable. This analysis raises concern about placing too much emphasis on densification as a policy tool for “smart growth.” Too much attention and effort is expended on increasing density of development and there is little evidence of benefits of doing so. The positive aspects of density results from favorable market forces, rather than regulatory forces

Hot mantle upwelling across the 660 beneath Yellowstone

P-to-s receiver functions mapped to depth through P and S body-wave tomography models image continuous 410 and 660 km discontinuities beneath the area covered by USArray prior to the year 2011. Mean depths to the 410 and 660 km discontinuities of 410 and 656 km imply a mantle transition zone that is about 4 km thicker than the global average and hence has a slightly cooler mean temperature and/or enhanced water content. Compared to the mean 660 depth beneath this ~2000 km wide area, the 660 beneath the Yellowstone hotspot is deflected upward by 12–18 km over an area about 200 km wide. This is the most anomalous shallowing of the 660 imaged and its horizontal extent is similar to the area where P and S tomography image low-velocity mantle extending from the top of the transition zone to about 900 km depth. Together, these results indicate a high-temperature, plume-like upwelling extending across the 660. The depth of 410 km discontinuity beneath the Yellowstone region is within 5 km of the mean depth implying that the plume is vertically heterogeneous and possibly discontinuous. Tomography indicates a similar vertically heterogeneous thermal plume. The irregular plume structure may be intrinsic to the dynamics of upwelling through the transition zone, or distortion may be caused by subduction-induced mantle flow. Topography of the 410 and 660 confirms that subducted slabs beneath the western U.S. are highly segmented, as inferred from recent tomography studies. We find no evidence of regionally pervasive velocity discontinuities between 750 and 1400 km depth. The plume's depth of origin within the lower mantle remains uncertain

Proceedings of a Workshop on Interactive Graphics for Transportation Planners

The workshop attracted transportation planners from transit and regional planning agencies, consulting firms, and local governments. It explored the use of interactive graphics coupled with multi-modal transportation planning. Several key aspects of the use of interactive graphics were explored in panel discussions and demonstration workshop sessions. These aspects included the evolution of interactive graphics technology, the structured application of this technology in implementation, the operational environment, impacts on planning agencies and future applications of this technology. The demonstration of applications was made possible by use of Metro\u27s EMME/2 system. Metro is the Metropolitan Planning Organization (MPO) for the Portland area. Metro is the first planning jurisdiction in the United States to use EMME/2, so Metro\u27s experience with the implementation of the system is particularly valuable. After acquiring the Urban Transportation Planning System (UTPS) in 1977, Metro began to look for new technology to better serve their regional transportation planning needs. In 1983, Metro acquired the EMME/2 system. Metro personnel who have used the system on a day-to-day basis have valuable insight into the functional aspects of this new technology

Effects of Light Rail Transit in Portland: Implications for Transit-Oriented Development Design Concepts

In the Portland, Oregon, region many local planners have embraced the neotraditional planning concept in the form of transit-oriented development (TOD). One of the primary components of transit-oriented development, light rail transit (LRT), has been in place in Portland long enough to provide data for analysis. Because neotraditional planners often emphasize LRT as a crucial element in decreasing auto use and in encouraging high-density development, this paper examines the effects of LRT in the Portland region including mode share, density, and property values. The empirical analysis provides evidence that light rail alone has not been sufficient to have an appreciable impact on development patterns, residential density, auto ownership, and transit modal behavior, although there has been some positive effect of rail on single-family property values. There has also been less of a decline in transit use and slower growth in two-car households in the LRT corridor as compared to a parallel bus corridor. The small positive effects of LRT may indicate the beginning of a self-selection in housing location choice wherein persons desiring rail transit choose to live where it is available. This assessment of the evidence in terms of impacts on development trends indicates the extent to which consumer preferences have responded to LRT investments. This kind of assessment is needed to provide the basis for estimating travel mode shares and market shares for dispersed and concentrated development forms. Examination of data suggests that it may be advisable for planners to entertain more modest expectations of LRT

A Proposed Method of Transportation Feature Identification

Geographic information systems (GIS) are being increasingly deployed by transportation agencies to help them display, review, and utilize data. The primary items of interest are transportation facilities and services, which may take the form of highways, airports, bus routes, and seaports, among others. Using GIS software, transportation facilities are represented as geometric shapes; i.e., points, lines, and areas. However, it is increasingly apparent to GIS users in the field of transportation that a geometry-based approach is not sufficient. The offered solution is to develop a feature-based GIS approach for transportation. The central requirement of such an approach is to have an unambiguously identified set of transportation features and a means of locating related features and attributes on or adjacent to the transportation features. For linear transportation features, the common location referencing system (LRS) is also linear. Usually based on milepoint offsets from a beginning point, linear LRSs are widely used by transportation agencies to locate data stored in numerous legacy databases. Some agencies may have multiple linear LRSs for various applications or topical areas. Data users unfamiliar with linear LRSs have difficulty using highway data provided by transportation agencies, and the correlation of linear and non-linear LRSs is generally quite difficult. The result is that sharing of digital road map databases within and among organizations is difficult since there are no consistent ways of representing transportation features, and different decision rules exist as to what features to include and how they are identified. Numerous efforts are underway to develop a national standard for linear LRS design and implementation, including a set of field procedures to ensure that needed accuracy is achieved. This paper will describe a means to unambiguously define transportation features using a simple set of naming rules. These rules will support linear and other forms of LRS for all types of transportation features, including airports, seaports, railroads, highways, transit services, bridges, intersections, signs, and related facilities and services. Such features may be displayed at multiple scales as point, line, and area graphical objects

Light Rail Transit Impacts in Portland: The First Ten Years

This paper examines how the first decade of light rail transit (LRT) in the Portland region has affected auto ownership, mode share, density, and property values. The empirical analysis provides evidence that light rail has had some positive effect of rail on single-family property values, transit use, and slower growth of two-plus car households in the outer part of the LRT corridor as compared to an outer part of a parallel bus corridor. These effects may be the result of households self-selecting to make housing location decisions where LRT is located, rather than current households changing mode. This assessment of the evidence indicates the extent to which consumer preferences have responded to LRT investments. This kind of assessment is needed to provide the basis for estimating travel mode shares and market shares for dispersed and concentrated development forms. Examination of data suggests that it may be advisable for planners to entertain more modest expectations of LRT

Sharing Transportation GIS Data

Updating and maintaining Geographic Information Systems-Transportation data (GIS-T data) is proving difficult. Different database formats needed to support diverse applications leads to inconsistencies and inaccuracies, and duplication in updating. Dueker and Butler (1998) have proposed an Enterprise GIS-T data model that unbundles the various components of transportation data (network links, cartography, and attributes) to facilitate generating application-specific networks, and which eases updating and maintenance. However, developers of existing application-specific databases that employ integrated data models that bundle the network link with cartography and attributes are reluctant to step back to an intermediate form for managing their data. Consequently, attention is given in this report to the development of a method of incorporating transportation system changes directly to existing application- specific networks

ORBIT: The Oregon Road Base Information Team, A Draft Summary Report

It is clear that transportation organizations across the nation are integrating GIS into operations at many different levels—from day to day use for data display, to full-scale enterprise level integration for operations, inventory management, research and a variety of other purposes. The cost of building and maintaining a current and accurate GIS database can be substantial within any given organization. For some smaller level organizations—small counties, cities or special districts, the cost of gathering data, organizing it and implementing systems within expensive software on an expensive operating platform can be downright discouraging. Also, as more complex data structures are accumulated a window for more comprehensive modeling and analysis of regional issues is opened. Each of these trends alone provide ample incentive to develop data standards that can be applied to all systems to facilitate data sharing between organizations for system development, system update, or project specific purposes. Taken together these trends provide an imperative to develop data-sharing standards

Pedestrian Infrastructure Improvements: Effects on Transit Use and Perceptions of the Pedestrian Environment in Portland\u27s Roseway Neighborhood

Over the past two years the Pedestrian Transportation (PTP) of the City of Portland has been engaged in a project to encourage walking and transit use through targeted infrastructure improvements. These improvements are intended to enhance pedestrian access to transit service by aiding street crossing and providing more amenities at bus stops. Other improvements include landscaping, sidewalks, curb extensions and ramps, and improved street lighting. One of the basic assumptions of this project is that the pedestrian environment is related to transportation choices. This report explores that assumption

The Effects of Roadway Capacity on Peak Narrowing - Evidence from 1995 NPTS

Spreading of the peak is one effect of increased peak-period congestion. Due to peak spreading, the travel-time impact of congestion is mitigated for some travelers, but the inconvenience of traveling at a less-preferred time also has a cost. Alternatively, increases in capacity have their impacts on peak-period congestion mitigated by a narrowing of the peak. This reduces the travel-time savings, but it generates a benefit for those traveling closer to their preferred times. This benefit from capacity improvements has largely been ignored, and one reason is the difficulty of quantifying the effect. This paper reports on some crude attempts to quantify the peak-narrowing effect of increased capacity. Using 1995 Nationwide Personal Transportation Survey (NPTS) data, this study investigates how workers in Metropolitan Statistical Areas (MSAs) in the US respond to roadway capacity differences in terms of changing their departure time to work. It is assumed that there is some distribution of travel times given by a mean and some measure of deviation from the mean. Peak narrowing is then measured by decreases in the deviation from the mean. The peak narrowing effects are modeled for both the morning commute and all departures from home for work at any time of the day. As expected, in urban areas with higher roadway capacity per capita, workers tend to depart from home closer to the peak time. For the morning commute, the model estimates that each one-percent increase in lane-miles per capita results in workers departing from home about 5.75 percent closer to the peak time. The effects of roadway capacity are found to be statistically significant in both models