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Wallingford Center, CT, United States

Fitzpatrick K.,Texas A&M University | Brewer M.,Texas A&M University | Eisele W.,Texas A&M University | Zhang Y.,Texas A&M University | And 3 more authors.
Transportation Research Record | Year: 2012

Left-turn movements at intersections, including driveways - especially movements that are made from lanes that are shared with through traffic - cause delays and adversely affect safety. Although some left-turn warrants have been updated, many agencies still use research performed by M. D. Harmelink in the mid-1960s. Most states use procedures that are based on Harmelink's work, but several limitations have been identified. Economic analysis can provide a useful method for combining traffic operations and safety benefits of left-turn lanes to identify situations in which left-turn lanes either are or are not justified economically. This project used a benefit-cost approach to determine when a left-turn lane would be justified. The steps included simulation to determine delay savings from installing a left-turn lane, crash costs and crash reduction savings determined from safety performance functions and crash modification factors available in the Highway Safety Manual, and construction costs. Left-turn lane warrants were developed for rural two-lane highways, rural four-lane highways, and urban and suburban roadways. In addition, warrants for bypass lanes were developed for rural two-lane highways. Source


Allen J.,Regional Transportation Authority | Levinson H.,5305 Ashlar Village
Transportation Research Record | Year: 2012

During the first third of the 20th century, 16 commuter rail operations in major North American metropolitan areas adopted electric traction. Ten of these electrifications survive. The other six were discontinued between 1929 and 1949, although parts of the alignments of some properties have been returned to regional transit use. With a comparison of the histories of the former electric railroads with those of operations that survived, the reasons for their discontinuance are investigated. Perhaps unexpectedly, the Great Depression does not solely account for the demise of most of these lines. Instead, major geographic barriers precluding direct downtown service and the construction of new highway links appear to have been at least as important. Furthermore, all surviving electrifications addressed practical operating needs. However, no installations undertaken as technological test beds or in response to competing lines have survived. Source


Allen J.G.,Regional Transportation Authority | Levinson H.S.,5305 Ashlar Village
Transportation Research Record | Year: 2011

Traditional rail rapid transit systems are primarily limited to central cities, but a modern variant, regional rapid transit (RRT), extends far enough into suburbs to be considered truly regional in scope. RRT uses automatic train driving, other advanced technologies, long station spacing, and park-and-ride lots to serve suburban as well as city travel. Inaugurated between 1969 and 1979, RRT operations in several regions (Philadelphia, Pennsylvania; Boston, Massachusetts; San Francisco, California; Washington, D.C.; and Atlanta, Georgia) combined advanced rapid transit technology with station spacing and market functions akin to inner-zone to midrange commuter rail. To establish similarities and differences between the properties of RRT and other rail systems, data are analyzed for these and other rapid transit systems, as well as for historically established commuter railroads. RRT operations today face challenges of aging infrastructure but continue to be vital in the areas that they serve and have undergone incremental expansion in some instances. Source


Holguin-Veras J.,Rensselaer Polytechnic Institute | Jaller M.,Rensselaer Polytechnic Institute | Destro L.,Rensselaer Polytechnic Institute | Ban X.J.,Rensselaer Polytechnic Institute | And 2 more authors.
Transportation Research Record | Year: 2011

Several findings call into question current practices. The chief conclusion is that the accuracy of freight generation (FG) and freight trip generation (FTG) models depends on the consistency between the model's structure and actual FG-FTG patterns, the degree of internal heterogeneity of the economic and land use aggregation used to estimate the model, and the appropriateness of the spatial aggregation procedure used to obtain the desired FG-FTG estimates. Relative to model structure, the paper establishes strong reasons to treat FG and FTG as separate concepts, because the latter is the output of logistic decisions, whereas the former is determined by the economics of production and consumption. The connection between business size variables-for example, employment-and FG is relatively strong because they are economic input factors, whereas the one with FTG is weaker because inventory and transportation costs come into play. Thus it is generally not correct to assume proportionality between FTG and business size or to assume that using constant FTG rates could be problematic. For instance, only 18% of the industry sectors in New York City exhibit constant FTG rates per employee. For economic and land use aggregation, the finer the level of detail the better, as independent variables have a better chance to explain FG-FTG. In the case of spatial aggregation, the correct aggregation procedure depends on the underlying disaggregate model. For a FG-FTG model to work well, both economic and land use and spatial aggregations must be appropriate. Source


Gattis J.L.,University of Arkansas | Levinson H.S.,5305 Ashlar Village | Gluck J.S.,AECOM Technology Corporation | Barlow J.M.,Accessible Design for the Blind | And 2 more authors.
Transportation Research Record | Year: 2010

Driveways are the link between public roadways and the abutting activities that they serve. Driveways serve a wide range of activities in a variety of contexts. Driveway design guidelines have traditionally focused on accommodating motor vehicles, but in recent years, growing emphasis has been placed on a broader range of issues, such as better managing access and accommodating all modes, including pedestrians and bicyclists. How well driveways are designed affects the safety and mobility of not only motorists but also bicyclists and pedestrians. This paper draws from research performed for NCHRP Project 15-35, Geometric Design of Driveways. It discusses multimodal driveway design considerations and provides design guidelines that recognize the needs of pedestrians (including those with disabilities and transit users) and bicyclists. Source

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