Analysis of Saturation Flow at Signalized Intersections

The accuracy of saturation flow values is of prime importance when determining the capacity of signalized intersections. The objective of this study was to collect a large sample of field measurements so that reliable saturation flow values could be obtained and the factors affecting saturation flow could be identified. The results identified several factors which had significant influence on saturation flow. A formula was recommended for use in estimating an appropriate saturation flow value for a specific lane on an approach to an intersection. Adjustment factors were applied to a base\u27\u27 saturation flow value. Adjustments were developed for the following factors; location in city, city population, vehicle type and turning maneuver, gradient, width of lane, turning radius (jar right-turning vehicles), pedestrian activity, type of lane, speed limit, and light condition

Accident Rates by Vehicle Type

This report describes the calculation of accident rates for different vehicle types, using vehicle-miles travelled as the measure of exposure. Rates are reported for passenger cars, single-unit trucks, combination trucks, buses, and motorcycles on various highway types. Highway types are broken down by functional classificaion, administrative classification, number of lanes, and rural or urban location. Generally motorcycles had the highest rates and passenger cars had the lowest, although this varied by highway type

Child Restraint Usage in Kentucky (Pre-Legislation)

In an attempt to increase child restraint usage, a law was enacted by the 1982 Kentucky Legislature requiring use of child restraints for children forty inches or less in height. To evaluate the effectiveness of this law, a usage survey had to be completed before the law became effective. Objectives of this study were to determine statewide child restraint usage and statistics relating to improper usage. Seatbelt usage of drivers was also analyzed. A statewide child restraint usage rate of 14.4 percent was obtained. Only 44 percent of restraints were coded as used properly. Several factors, such as population, age of child, and driver restraint usage, were related to child restraint usage. The specific restraint brand was noted and a few, such as the Strolee and Bobby Mac, were the most common. The major overall improper usage was failure to tether the restraint as required. A statewide driver restraint usage rate of 4.2 percent was found

Analysis of Lost Times at Signalized Intersections

When determining the capacity of a signalized intersection, knowledge of certain traffic parameters is necessary. The previous investigation conducted under this study dealt with an analysis of saturation flow values. The objective of this investigation was to determine appropriate values to use for lost times at signalized intersections. The lost times at the beginning and ending of the phases were analyzed, as well as lost times during the phase due to the interference of pedestrians, local buses, and opposing traffic for left turns. Factors affecting those lost time values were identified. The lost time values, along with the previously identified saturation flow values, permit the calculation of capacity at signalized intersections and may be used as input when using computer models to simulate and optimize signal systems. Base values of 1.40 and 1.67 were found for beginning and ending lost time, respectively. Formulas were given that considered the effect of several factors on beginning and ending lost times. Case studies illustrating the use of those formulas are given

Plasticity in current-driven vortex lattices

We present a theoretical analysis of recent experiments on current-driven vortex dynamics in the Corbino disk geometry. This geometry introduces controlled spatial gradients in the driving force and allows the study of the onset of plasticity and tearing in clean vortex lattices. We describe plastic slip in terms of the stress-driven unbinding of dislocation pairs, which in turn contribute to the relaxation of the shear, yielding a nonlinear response. The steady state density of free dislocations induced by the applied stress is calculated as a function of the applied current and temperature. A criterion for the onset of plasticity at a radial location $r$ in the disk yields a temperature-dependent critical current that is in qualitative agreement with experiments.Comment: 11 pages, 4 figure

Weak turbulence theory of the non-linear evolution of the ion ring distribution

The nonlinear evolution of an ion ring instability in a low-beta magnetospheric plasma is considered. The evolution of the two-dimensional ring distribution is essentially quasilinear. Ignoring nonlinear processes the time-scale for the quasilinear evolution is the same as for the linear instability 1/t_ql gamma_l. However, when nonlinear processes become important, a new time scale becomes relevant to the wave saturation mechanism. Induced nonlinear scattering of the lower-hybrid waves by plasma electrons is the dominant nonlinearity relevant for plasmas in the inner magnetosphere and typically occurs on the timescale 1/t_ql w(M/m)W/nT, where W is the wave energy density, nT is the thermal energy density of the background plasma, and M/m is the ion to electron mass ratio, which has the consequence that the wave amplitude saturates at a low level, and the timescale for quasilinear relaxation is extended by orders of magnitude

Late-Type Stars in M31. I.: A Photometric Study of AGB Stars and Metallicity Gradients.

We have imaged five 7\arcmin \x 7\arcmin\ fields in M31 spanning galactocentric radii from 4 to 32 kpc along the SW-major axis. The fields were observed through two broad-band (\V\ and \I) and two narrow-band (\CN\ and \TiO) filters. The broad-band data were used to construct \IvsVI\ color-magnitude diagrams (CMDs) and, in some of our fields, we found significant numbers of stars in the Cepheid instability strip. A distance modulus for the Cepheids in the middle field was found that agreed well with other values in the literature values. The width of the giant branch (GB) in the \IvsVI\ CMD of all 5 fields was investigated, and we show that in four of the fields a likely explanation for the GB width is a combination of {\it both} metallicity and mass variations. Using the broad-band data, the asymptotic giant branch (AGB) luminosity functions (LFs) were measured in the five fields, and we show that differences exist between these LFs. We speculate on how the different star forming histories in the fields may lead to the observed AGB LFs and GB widths. Using the narrow-band data along with the broad-band data we separated the AGB stars into carbon-rich (C) and oxygen-rich (M) types. The carbon stars LFs were used to obtain an estimate for the distance modulus of M31 which agrees with the value derived from Cepheids. The ratio of C- to M-stars (C/M) is believed to be an indicator of gaseous chemical abundance at the time of formation of these stars. We show that the C/M ratio increases smoothly with galactocentric distance, suggesting an inverse correlation with metallicity. This is the first demonstration of this effect within a single extragalactic system. We find that differences in the width of the GB and the AGB LFs do not significantly affect the C/M ratio. We consider the effect of the increasing C/M ratio on the ISM in M31, and cite evidence in favor of a model where the grain composition in M31 is a function of galactocentric distance.Comment: UUencoded compressed postscript, 3 Figs. available on request. (Contact [email protected]

Survey of Effectiveness of Transportation Services

With increased emphasis on public accountability and program evaluation, the need for effectiveness measures to indicate the extent to which an agency\u27s goals and objectives are being met is increasingly apparent. A research study was undertaken to establish and implement a procedure for monitoring the effectiveness of transportation services in Kentucky. Quantitative data for many of the effectiveness measures were obtainable only through responses from the public. Surveys of licensed drivers and bus riders were selected as data sources. This report addresses the procedures and results of the two surveys. Responses were received from 35.5 percent of the 10,000 licensed drivers who were sent questionnaires and 26.0 percent of the 4,560 bus riders. Results from the surveys were summarized into the following areas: (l) survey response, (2) personal information, (3) satisfaction with transportation services, (4) inadequate transportation services, (5) drivers\u27 complaints and compliments, (6) future government spending for transportation, (7) problems getting to various destinations, (8) use of other modes of transportation, (9) opinions on laws or government regulations, and (10) bus rider survey

Evaluation of Thermal Imaging Technology for Commercial Vehicle Screening

Brake and tire violations are common problems identified through commercial vehicle inspections. Identifying and correcting these types of problems before a crash occurs can produce significant safety benefits. Thermal imaging technology can be used by commercial vehicle enforcement to screen vehicles as they approach a weigh station to determine if they may have flat tires and inoperable brakes. The vehicles do not have to be stopped at a weigh station to be screened. Kentucky currently has three stations outfitted with thermal imaging technology. The objectives of this study were to evaluate the benefits of using the thermal imaging cameras to identify brake and tire problems and to develop recommendations for how enforcement personnel can receive the most benefits from this technology. The data presented in this report include: 1) a summary of previous research, 2) evaluations of the technology, 3) on-site data collection at a Kentucky weigh station, 4) an interview with one of Kentucky’s primary users of the technology, and 5) an analysis of Kentucky inspection data, specifically, brake and tire violations and vehicle out-of-service (OOS) rates. A Federal Motor Carrier Safety Administration (FMCSA) evaluation concluded that the OOS rate for vehicles pinpointed via thermal imaging camera systems was 59 percent, whereas the OOS rate for conventional inspection was only 19 percent. Facilities with a thermal imaging system recorded a higher percentage of tire and brake violations per inspection as well as a higher vehicle out-of-service (VOOS) rate than facilities without a thermal imaging camera. However, the effectiveness of thermal imaging technology was significantly influenced by whether law enforcement embraced it as well as by inspectors’ proficiency operating the systems. This study recommends that enforcement staff who can access thermal imaging technology receive periodic training on its operation, then graduate to a practicum that lets them use the technology under expert supervision. Promotional materials that highlight the value of thermal imaging technologies should be distributed to all Kentucky enforcement personnel. In addition, methods and enforcement mechanisms should be identified so that personnel can be held accountable for using the technology