Evaluation of Alternative Intersections and Interchanges: Volume II—Diverging Diamond Interchange Signal Timing

This report presents findings from field studies of operations at diverging diamond interchanges (DDIs) in Salt Lake City, Utah and Fort Wayne, Indiana. These discuss optimization of signal offsets both within the DDI, and with the DDI integrated as part of an arterial corridor. Optimization of Fort Wayne, Indiana corridor comprising the DDI and three neighboring intersections yielded an annualized user benefit of $564,000, when assessing origin-destination paths both along the arterial and for movements to and from the freeway. This is the first field study of DDI offset optimization with neighboring intersections. Additionally, a pilot study was carried out in Salt Lake City on a new phasing scheme that incorporated a “holdback” phase into the signal sequence that delayed vehicles exiting the ramp in order to better coordinate their arrival at the downstream intersection, increasing the percent on green from 53% to 92%. The report concludes with a discussion of practical issues pertaining to DDI signal timing and provides a series of guidelines to assist in the design of new signal timing plans for future DDI deployments

Deep Sequencing of the HIV-1 env Gene Reveals Discrete X4 Lineages and Linkage Disequilibrium between X4 and R5 Viruses in the V1/V2 and V3 Variable Regions

ABSTRACT HIV-1 requires the CD4 receptor and a coreceptor (CCR5 [R5 phenotype] or CXCR4 [X4 phenotype]) to enter cells. Coreceptor tropism can be assessed by either phenotypic or genotypic analysis, the latter using bioinformatics algorithms to predict tropism based on the env V3 sequence. We used the Primer ID sequencing strategy with the MiSeq sequencing platform to reveal the structure of viral populations in the V1/V2 and C2/V3 regions of the HIV-1 env gene in 30 late-stage and 6 early-stage subjects. We also used endpoint dilution PCR followed by cloning of env genes to create pseudotyped virus to explore the link between genotypic predictions and phenotypic assessment of coreceptor usage. We found out that the most stringently sequence-based calls of X4 variants (Geno2Pheno false-positive rate [FPR] of ≤2%) formed distinct lineages within the viral population, and these were detected in 24 of 30 late-stage samples (80%), which was significantly higher than what has been seen previously by using other approaches. Non-X4 lineages were not skewed toward lower FPR scores in X4-containing populations. Phenotypic assays showed that variants with an intermediate FPR (2 to 20%) could be either X4/dual-tropic or R5 variants, although the X4 variants made up only about 25% of the lineages with an FPR of <10%, and these variants carried a distinctive sequence change. Phylogenetic analysis of both the V1/V2 and C2/V3 regions showed evidence of recombination within but very little recombination between the X4 and R5 lineages, suggesting that these populations are genetically isolated. IMPORTANCE Primer ID sequencing provides a novel approach to study genetic structures of viral populations. X4 variants may be more prevalent than previously reported when assessed by using next-generation sequencing (NGS) and with a greater depth of sampling than single-genome amplification (SGA). Phylogenetic analysis to identify lineages of sequences with intermediate FPR values may provide additional information for accurately predicting X4 variants by using V3 sequences. Limited recombination occurs between X4 and R5 lineages, suggesting that X4 and R5 variants are genetically isolated and may be replicating in different cell types or that X4/R5 recombinants have reduced fitness

Analysis of Peer Intersection Data for Arterial Traffic Signal Coordination Decisions

This is the author-accepted manuscript version of Day, C.M., T.M. Brennan, H. Premachandra, J.R. Sturdevant, and D.M. Bullock, “Analysis of Peer Data on Intersections for Decisions About Coordination of Arterial Traffic Signal,”Transportation Research Record: Journal of the Transportation Research Board, No. 2259, Transportation Research Board of the National Academies, Washington, D.C., pp. 23–36, 2011, copyright National Academy of Sciences.http://dx.doi.org/10.3141/2259-03 Its corresponding poster can be found here:http://docs.lib.purdue.edu/atspmw/2016/Posters/3

Court Strategy

This session focuses on the following issues: (1) access to the courts, (2) secrecy of court documents and settlements, (3) court bias, and (4) public education and tools. The panelists present possible solutions for the issues discussed

Sequence Optimization at Signalized Diamond Interchanges Using High-Resolution Event-Based Data

Signalized diamond interchanges are pairs of ramp intersections characterized by interlocked left turns and relatively close spacing. This paper describes a series of performance measures derived from high-resolution signal controller event data that can be used to optimize the internal phase sequence and offset to improve traffic flows within diamond interchanges and to assess the progression of the interior movements qualitatively and quantitatively. The new heuristic developed in this paper improves on traditional green band optimization techniques by incorporating actual demand profiles measured in the field. A field analysis was performed on a diamond interchange at I-69 and 96th Street in northwest Indianapolis, Indiana, where the existing sequence data were collected and used to model the alternative sequences to identify the optimal sequence. Interior operations were improved under the optimized settings: the percentage of vehicle arrivals on green increased by 19% during the 09:00-to-15:00 midday plan. Video observations were used to corroborate the data and are included in a video synthesis of the time–space trajectories. </jats:p

Integrating Traffic Signal Performance Measures into Agency Business Processes

This report discusses uses of and requirements for performance measures in traffic signal systems facilitated by high-resolution controller event data. Uses of external travel time measurements are also discussed. The discussion is led by a high-level synthesis of the systems engineering concepts for traffic signal control, considering technical and non-technical aspects of the problem. This is followed by a presentation of the requirements for implementing data collection and processing of the data into signal performance measures. The remaining portion of the report uses an example-oriented approach to showing a variety of uses of performance measures for communication and detector system health, quality of local control (including capacity allocation, safety, pedestrian performance, preemption, and advanced control analysis), and quality of progression (including evaluation and optimization)

Evaluation of Special Event Traffic Management: The Brickyard 400 Case Study

This paper reports on the anonymous tracking of Bluetooth enabled consumer electronic devices to measure the travel time, or space mean speed, of travelers. This sampling technique was deployed at six interstate locations and two signalized arterials in the Indianapolis, IN metropolitan area the week of the NASCAR Brickyard 400. The week prior to the race before data was also collected from a subset of those sites. The day of the race, almost 19,000 unique MAC address were captured at the eight locations. From that information real-time travel time estimates were provided to Indiana Department of Transportation (INDOT) mobile data terminals. After the race, the data was processed to obtain travel time plots and origin destination matrixes to provide a quantitative evaluation of race day traffic management operations. Selected reports and charts from that analysis are discussed in the paper

Detector-Free Optimization of Traffic Signal Offsets with Connected Vehicle Data

It has recently been shown that signal offset optimization is feasible using vehicle trajectory data at low levels of market penetration. This study performs offset optimization on two corridors using this type ofdata. Six weeks oftrajectory splines were processed for two corridors including 25 signalized intersections, in order to create vehicle arrival profiles, using a proposed procedure called virtual detection. After processing and filtering the data, penetration rates between 0.09-0.80% were observed, varying by approach. The arrival profiles were statistically compared against those measured with physical detectors, with the majority of the approaches showing statistically significant goodness-of-fit at a 90% confidence level. Finally, the virtual detection arrival profiles were used to optimize offsets, and compared against a solution derived from physical detector arrival profiles. The results demonstrate that virtual detection can produce good quality offsets with current market penetration rates of probe data. The study also includes a sensitivity analysis to the sample period, which shows that two weeks of data may be sufficient for data collection at current penetration rates