Reliability, Flexibility, and Environmental Impact of Alternative Arterial Offset Optimization Objective Functions

A wide variety of alternative optimization objective functions, such as minimizing stops, minimizing delay, and maximizing arrivals on green, has been reported in the literature. An extensive literature evaluates these alternative objective functions with models. This paper reports on the field deployment of these alternative optimization functions, developed with high resolution controller data, to adjust offsets on an arterial system of eight coordinated signals. The deployment consisted of a 1-week base data collection and four 1-week deployments of offset plans developed with four alternative optimization objective functions. Travel times of anonymous probe vehicles were measured during the study period to evaluate the impact of these alternative optimization functions on corridor travel time. All objective functions were successful in reducing median corridor travel time significantly. Median travel time decreased by more than 1 min in both directions on the 5-mi corridor. Travel time reliability, as quantified by the difference between 75th and 25th percentile travel times, was improved for the busiest portion of the day. A lower bound of the estimated annual savings on user costs was $472,817, with an associated reduction in carbon dioxide emissions of 197 tons per year. </jats:p

Mineral phosphorus drives glacier algal blooms on the Greenland Ice Sheet

Melting of the Greenland Ice Sheet is a leading cause of land-ice mass loss and cryosphere-attributed sea level rise. Blooms of pigmented glacier ice algae lower ice albedo and accelerate surface melting in the ice sheet’s southwest sector. Although glacier ice algae cause up to 13% of the surface melting in this region, the controls on bloom development remain poorly understood. Here we show a direct link between mineral phosphorus in surface ice and glacier ice algae biomass through the quantification of solid and fluid phase phosphorus reservoirs in surface habitats across the southwest ablation zone of the ice sheet. We demonstrate that nutrients from mineral dust likely drive glacier ice algal growth, and thereby identify mineral dust as a secondary control on ice sheet melting.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Performance Measures for Traffic Signal Systems: An Outcome-Oriented Approach

This monograph is a synthesis of research carried out on traffic signal performance measures based on high-resolution controller event data, assembled into a methodology for performance evaluation of traffic signal systems. High-resolution data consist of a log of discrete events such as changes in detector and signal phase states. A discussion is provided on the collection and management of the signal event data and on the necessary infrastructure to collect these data. A portfolio of performance measures is then presented, focusing on several different topics under the umbrella of traffic signal systems operation. System maintenance and asset management is one focus. Another focus is signal operations, considered from the perspectives of vehicle capacity allocation and vehicle progression. Performance measures are also presented for nonvehicle modes, including pedestrians, and modes that require signal preemption and priority features. Finally, the use of travel time data is demonstrated for evaluating system operations and assessing the impact of signal retiming activities

Quantifying Benefits of Traffic Signal Retiming

Improvements in the quality of service on a signalized intersection or arterial can be interpreted as a reduction in the user cost of service, which is expected to induce demand based on economic theory. This report presents a methodology for measuring and interpreting changes to user costs, and determining whether demand was induced. High-resolution signal event data and Bluetooth device MAC address matching are demonstrated in three case studies with the purpose of quantifying the impacts of changes in signal timing plans. In the first case study, 21 months of vehicle volume data are used to test whether demand was induced by optimizing offsets on a Saturday plan. In the second case study, the increase in demand for pedestrian service is quantified with respect to the implementation of an exclusive pedestrian phase using an econometric model taking the effects of season, weather, and special events into account. Finally, the third case study demonstrates the use of vehicle travel time data in quantifying changes in user costs and environmental impact (tons of carbon). A method of describing changes in travel time reliability is also presented

Citizen Band (CB) Radio Communication Commenting on Indiana State Police Enforcement Activity

This audio was recorded from Citizen Band (CB) radio traffic on Channel 19 adjacent to mile marker 127.8 on I-65 in Indiana (Latitude 39.918554, Longitude -86.329367). The audio recording represents selected transmissions recorded at approximately 9:30am on 21 July 2010 documenting the public perception of an Indiana State Police enforcement detail that was occurring along I-65 and I-865 in Boone and Marion County. Approximately 12 different Indiana State Police personnel were involved in the enforcement detail at the time of the recording

Visualizations of Travel Time Performance Based on Vehicle Reidentification Data

This paper provides a visual reference of the breadth of arterial performance phenomena based on travel time measures obtained from reidentification technology that has proliferated in the past 5 years. These graphical performance measures are revealed through overlay charts and statistical distribution as revealed through cumulative frequency diagrams (CFDs). With overlays of vehicle travel times from multiple days, dominant traffic patterns over a 24-h period are reinforced and reveal the traffic behavior induced primarily by the operation of traffic control at signalized intersections. A cumulative distribution function in the statistical literature provides a method for comparing traffic patterns from various time frames or locations in a compact visual format that provides intuitive feedback on arterial performance. The CFD may be accumulated hourly, by peak periods, or by time periods specific to signal timing plans that are in effect. Combined, overlay charts and CFDs provide visual tools with which to assess the quality and consistency of traffic movement for various periods throughout the day efficiently, without sacrificing detail, which is a typical byproduct of numeric-based performance measures. These methods are particularly effective for comparing before-and-after median travel times, as well as changes in interquartile range, to assess travel time reliability

Combined effect of algae and dust on snow spectral and broadband albedo

The optical properties of snow can be strongly modified by the presence of a variety of impurities including mineral dust and snow algae. We made use of measured concentration of snow algae and mineral dust to parameterize the BioSNICAR radiative transfer model. Surficial snow samples were gathered during a field campaign on 7th July 2020 at the Presena glacier (Rhaetian Alps). We collected 18 samples of surface snow containing different amount of snow algae and mineral dust. Through radiative transfer simulations we estimated an average broadband albedo reduction of 7.4 +/- 6.1 % and 35.3 +/- 7.4 % compared to clean snow, caused by snow algae and mineral dust presence, respectively. When we considered the combined effect of snow algae and dust, we estimated a broadband albedo reduction equal to 40.8 +/- 8.4 %. We estimated an average instantaneous radiative forcing induced by snow algae, mineral dust and both impurities equals to 42.3 (+/- 36.1) W/m(2), 203.7 (+/- 45.5) W/m(2), and 211.8 (+/- 45.9) W/m(2), respectively.Using BioSNICAR simulations, we also tested a series of narrowband spectral indices to determine the concentration of mineral dust and snow algae from multi- and hyper -spectral data. Results showed that most spectral indices used for snow algae mapping are correlated also with mineral dust concentration. We found that only an index correlates uniquely with snow algae: the scaled band integral at 680 nm. A new spectral index, namely the Green Blue Normalized Index, is therefore proposed to discriminate mineral dust from snow algae when both impurities are present. The high spectral resolution of current (e.g. PRISMA, EnMAP) and future (e.g. CHIME, SBG) hyperspectral satellite missions will be fundamental to decouple the effect of mineral dust and snow algae on the optical properties of snow. In fact, from those data it is possible to calculate all narrowband indices presented in this study