Paul E Benson

A review of the development and application of the CALINE3 and 4 models

Abstract A description of the California Line Source Dispersion Model, CALINE, is given along with a brief history of its development. The model is based on the Gaussian plume methodology and is used to predict air pollutant concentrations near roadways. Predictions can be made for carbon monoxide, nitrogen dioxide and suspended particulates. There are two versions of the CALINE model in current use. CALINE3, published in 1979, replaced the virtual point approximation contained in earlier versions of the model with an equivalent finite line source representation and added a multiple link option. CALINE4, published in 1984, incorporated flexible input/output options including an option for modeling air quality near intersections. It also includes dispersion algorithms to account for vehicle-induced thermal turbulence and wind direction variability. CALINE4 is verified using results from five separate field studies. Comparisons to CALINE3 indicate modest improvements in the accuracy of the newer version.

The sequenced activity mobility simulator (SAMS): an integrated approach to modeling transportation, land use and air quality

The persistence of environmental problems in urban areas and the prospect of increasing congestion have precipitated a variety of new policies in the USA, with concomitant analytical and modeling requirements for transportation planning. This paper introduces the Sequenced Activity-Mobility Simulator (SAMS), a dynamic and integrated microsimulation forecasting system for transportation, land use and air quality, designed to overcome the deficiencies of conventional four-step travel demand forecasting systems. The proposed SAMS framework represents a departure from many of the conventional paradigms in travel demand forecasting. In particular, it aims at replicating the adaptative dynamics underlying transportation phenomena; explicitly incorporates the time-of-day dimension; represents human behavior based on the satisficing, as opposed to optimizing, principle; and endogenously forecasts socio-demographic, land use, vehicle fleet mix, and other variables that have traditionally been projected externally to be input into the forecasting process.

Modifications to the Gaussian vertical dispersion parameter, σz, near roadways

Estimates of the Gaussian vertical dispersion parameter σz are made using near roadway tower and ground level concentrations of CO and SF6 from four independent dispersion studies. The results indicate that the Gaussian model adequately describes the vertical distribution of vehicular emissions near the roadway. The active release of pollutants from vehicles is shown to yield greater initial vertical dispersion than would be expected from a similar passive release given neutral to stable atmospheric conditions. The initial value of σz near the roadway edge is relatively insensitive to surface layer stability, but significantly increases with decreasing wind speed. This is explained in terms of increased residence time at low wind speeds for emissions within the intensely turbulent mixing zone of the roadway. A method of combining a residence time model for initial σz and established vertical dispersion curves for passive releases is presented. Verification of the method using results measured under crosswind conditions to a distance of 100 m from the roadway yields no significant bias and an r.m.s. error of 28 %

Performance Review of a Quality Control/Quality Assurance Specification for Asphalt Concrete

A statistical review of 50 jobs recently completed by using California’s new quality control/quality assurance (QC/QA) specification for asphalt concrete is presented. Performance is contrasted to the quality achieved under method and end-result specifications. A cost analysis is made and issues related to verification are discussed. Improvements to the current specification are proposed. The data present clear evidence that the allowable tolerance of ±0.5 percent for asphalt content is too wide for current practice. Also, an increase in compaction variability for many QC/QA jobs could be controlled by adding an upper specification limit or adopting a two-sided volumetric specification. Although bid amounts did not increase, costs for QC/QA jobs went up approximately 3 percent to pay for bonuses allowed under the specification. Analysis of the contractor’s QC test data indicate that this increase is more than compensated for by projected reductions in future rehabilitation costs. However, a significant lack of agreement between the contractor QC and agency QA testing brings this finding into question. More rigorous verification of contractor-provided test results must be incorporated into the specification and the results analyzed before the cost-effectiveness can be determined.

Specification of Asphalt Concrete Using Total Quality Management Principles

The application of total quality management principles to asphalt concrete specifications is discussed. Specifications from 16 states are reviewed, and their attributes are critiqued. Verification procedures, statistical compliance measures, tolerance limits, lot definition, point of acceptance, density determination, and pay adjustment methods are recommended. The innovative concepts of contractor rating systems and warranties are examined briefly.

Modeling In-Use Construction Equipment Emissions for Highway Projects

Interest in estimating the air pollutant emissions that occur during highway project construction is increasing. This paper describes a construction emissions modeling framework with companion calculation methodologies. On the basis of bid data and field data collected from a range of highway construction projects, the modeling framework builds linkages between material quantities, equipment in-use hours, and pollutant emissions. The data calculation and processing methodologies can assist project analysts in creating emissions estimates across various construction operations at early environmental assessment stages when, typically, limited data are available for characterizing equipment activity for the future project. A hypothetical freeway-widening case study was used to demonstrate the application of the modeling framework and calculation methodologies. The example illustrates the frameworks ability to disaggregate emissions by construction operation; in the case analysis, hours of equipment use and emissions were greatest during roadway excavation and foundation work. Project analysts can also vary individual equipment characteristics that affect emissions, such as tier group (emissions certification standards), horsepower rating, equipment deterioration, and other factors in construction emissions analyses. For example, the emissions reduction benefits of shifting the equipment fleet to more stringent (Tier 4) emissions standards, especially as a strategy for reducing particulate emissions, can be quantified.

Process for Selecting Innovative Quality Assurance Practices for Materials

A process used in California to evaluate and implement innovative quality assurance practices for materials is described. The process involves three distinct phases: an audit of current practice, a structured evaluation of innovative practices, and the planned development of a materials management system (MMS). More than 1,600 performance elements were identified and categorized by material type. The quality assurance practice for each element was documented, and an assessment was made of its criticality on the basis of the consequence of failure. Testing and inspection workload for each materials category is determined through workload standards, sampling frequencies, and bid quantities. Analyses of these data reveal that testing and inspection costs are higher, dollar for dollar, for materials whose consequence of failure is low. This suggests that innovative practices such as quality control–quality assurance (QC/QA), pre- or postqualification of bidders, and warranties should be considered seriously for these materials. Evaluation of recent QC/QA projects indicates that adoption of innovative practices may not save dollars in the short term, but it can free resources for redirection to more critical needs and may provide higher quality work. The structured evaluation process used to assess the appropriateness of 18 primary and 11 supporting quality assurance options by performance element is described, and tables detail the decision logic used. Many of these options rely on an effective method for storing materials test information and tracking contractor and producer compliance. Design considerations for an MMS capable of providing this ability are discussed.

NONPARAMETRIC APPROACH TO MANAGING MATERIALS QUALITY

The normal distribution was tested for its goodness of fit to quality control data from 25 California Department of Transportation projects. The binder content and relative compaction of asphalt concrete were studied. In a significant number of cases, the assumption of normality was rejected. Closer examination of the observed distributions revealed instances of skewed, truncated, and bimodal distributions. Indications of nonnormality were found for a third of the asphalt content cases and nearly half of the relative compaction cases. An alternative nonparametric procedure for estimation of the percentage of material outside specification limits (POL) is proposed. Comparisons with the current methodology, which assumes that the data are normally distributed, indicated that somewhat lower, but arguably more accurate, estimates of POL are obtained by the nonparametric approach. Issues of accuracy and precision were addressed through a simulation study. The nonparametric method offers considerably greater statistical accuracy and power than the parametric approach when the data are not distributed normally and a performance comparable to that of the parametric approach when they are.