Suchergebnisse

A common rule of thumb for signalization in a city is one traffic signal for every 1,000 residents. When a city is depopulating, does this ratio apply when determining how many signals can be removed? The City of Detroit has lost 61% of its population since its peak. If signals were installed to serve the peak population, applying this rule of thumb, 61% of the signal inventory should be able to be removed. An operational analysis was performed on a random sample of the signal inventory of the City. Based on this sample, it was determined that 30% of the signal inventory could be removed and replaced with either two-way or all-way stop control, while still maintaining adequate levels-of-service for all approaches, resulting in a savings of US$460,000 to US$3,700,000 annually in operating costs. Other cities with declining populations should conduct similar analyses to reveal the extent of potential savings.

Minimum sign retroreflectivity standards issued by the Federal Highway Administration (FHWA) on January 29, 2008, have focused the attention of administrators and sign managers on improving the nighttime performance of traffic signs. To predict when a sign will need replacement, an agency will need to know when the retroreflectivity of signs with similar characteristics deteriorate to the minimum level established by the FHWA. Currently in the literature, there is limited information about the long-term deterioration behavior of ASTM Type III and IX signs. One way of achieving a better understanding of long-term sign deterioration is to establish an experimental sign retroreflectivity measurement facility (ESRMF). An ESRMF is an arrangement of signs in a controlled area that have their retroreflectivity measured at regular intervals to determine how it deteriorates as a function of time. This article shows how such a facility should look and why. A template is presented that can be used by agencies nationwide for collecting critical sign data to inform policy decisions.

Forecasting skilled construction labor demand ensures that the construction industry can train and supply an adequate workforce. Crucial to developing reliable forecasts is the collection of accurate and consistent data on which to base projections. This article summarizes research efforts to formally identify and collect quality economic and construction industry data intended for use in a labor forecast model. The methodology used to collect data for five key independent variables ( interest rate, material price, construction output, productivity, and real wage) and a dependent variable ( labor demand) from a variety of data sources is discussed. An assessment of the availability and quality of the data is made, and recommendations are given on how it can be improved. With these recommendations, more extensive data collection can be undertaken to produce accurate and consistent data. Doing so will provide the construction industry with more meaningful skilled labor data to support accurate forecasts for planning, recruitment, and retention efforts. This article fills a significant void in addressing construction industry data.

This article addresses paint centerline pavement marking retroreflectivity. The authors collect yellow centerline retroreflectivity data on two-lane highways, taking measurements in two directions. A paired t test on the data shows that there are differences and they are statistically significant. A field study is initiated to investigate the relationship between the direction the marking is painted and the retroreflectivity direction. The key result of this study is that paint centerline retroreflectivity values measured in the direction of paint striping are significantly higher than values measured in the opposite direction. Findings indicate that it is the lower retroreflectivity values of yellow centerlines (measured in the opposite direction from paint striping) that should be used to compare with the newly proposed Federal Highway Administration minimum standard because the drivers in that direction experience lower marking retroreflectivity at night. The implications for safety, for policy making, and for transportation asset management are significant.

This work aimed to determine, quantify, and present alternative approaches for agencies to meet the Federal Highway Administration's (FHWA) proposed minimum levels of retroreflectivity for signs. This study based these approaches on current North Carolina Department of Transportation sign maintenance practices and sought to minimize the cost and labor required to meet FHWA standards. This article offers four approaches: Nighttime visual inspection (current method), improved nighttime visual inspection procedures, sign inventory management system (no visual inspection), and combination of alternatives #2 and #3. This study ultimately recommends alternative #4, although it is the most costly. This article also recommends that an evaluation be made periodically to determine what benefits and improvement in sign condition, if any, have resulted from implementation.

Due to technological advances in data collection equipment, many transportation agencies are considering the use of mobile mapping systems: data collection vehicles equipped with a Global Positioning System receiver, an inertial navigation system, several digital cameras, and a computer. The host system is driven on a roadway, and data are collected on the fly. These raw data are then processed on a computer using photogrammetric software packages and input to an inventory database. Many transportation agencies are faced with the decision on using mobile mapping systems to improve their infrastructure data. This article presents a stepwise test protocol that transportation agencies can use to judge different data collection methods. Based on results of four experiments, the protocol provides guidance on different activities associated with the recommended evaluation process. The protocol is accompanied by information that transportation agencies may use as a benchmark for evaluating different inventory data collection methods.

Numerous unconventional intersection and interchange designs (UIIDs) exist with documented benefits, but implementation is slow. There are public, professional, and political barriers. Numerous papers explain the benefits of one design or compare designs, but few identify common barriers. This research surveyed transportation professionals to identify the barriers inhibiting the implementation of promising UIIDs and to identify solutions. Engineers believe that the public's main concerns are driver confusion and fear of the unknown. Survey results highlight education as important, and that public opinion generally improves once an UIID is constructed. Professionals and politicians want proof that a design will work and are reluctant to try nonstandard designs. An important political consideration is cost, but the life cycle cost can be competitive. We need guidelines to assist designers, increased focus on alternatives analysis, and inclusion of UIIDs in planning. This will make the designs more familiar to the public and decrease opposition.