Roger L Wayson

Development of traffic air quality simulation model

The U.S. Environmental Protection Agency currently promulgates the use of CAL3QHC to model the concentrations of carbon monoxide near roadway intersections. The steady-state and macroscopic methods used in this model represent rough approximations of the physical phenomena that occur at intersections and are unintuitive for the users. Therefore, the traffic air quality simulation model (TRAQSIM) was developed to create a theoretically more realistic (more natural), easier to understand, and more flexible modeling environment than CAL3QHC. Instead of the steady-state plume equations used in CAL3QHC, TRAQSIM models dispersion through the use of Gaussian puffs emitted from discrete moving sources in a traffic simulation environment. Although most components incorporated in TRAQSIM are not new, the combination of these components within a fully integrated environment is new and provides the potential for a more direct (more logical) expansion of modeling capabilities. As part of an initial validation assessme...

Effect of Vehicle Speed on Sound Frequency Spectra

The objective of this study was to investigate how the noise spectra generated by motor vehicles is influenced by vehicle speed. From this, a mathematical relationship that predicts the shift in frequency spectra, and the subsequent change in dominant frequency can be developed. The final result would be to implement this mathematical model within the framework of future highway traffic noise prediction models to allow for more accurate prediction of sound levels and better design of any noise abatement measures. This is necessary because the most common prediction scheme used in noise barrier design is based on use of the Fresnel number which is highly frequency dependent.

Comparison of Measured and Modeled Sound Levels in the Vicinity of Traffic Noise Barriers

A detailed noise prediction model was used to compare 11 highway noise barrier locations in Florida. Insertion losses, ground effects, shadow zones, and overall trends were determined or analyzed, or both. Each location was modeled using STAMINA2.0 (current FHWA regulatory model), STAMINA2.1 (Florida’s version of STAMINA2.0 with state-specific emission levels), the Traffic Noise Model (often referred to as TNM; this model will replace STAMINA2.0 in the year 2002), and the University of Central Florida Community Noise Model (CNM5.0). The modeled results were then statistically compared with the measured results. Statistical evaluation results were similar for all models for overall, absolute prediction compared with the measured value, with STAMINA2.1 being slightly better. All models provided adequate results, but ranges of error were significant. When the propagation components were explored, by comparing reference levels with those behind the barrier, the TNM was significantly better. The results also provided further insight into the benefited regions behind the barrier, a more detailed understanding of how the models perform for this complex interaction with the ground and sound wave, and how background levels change the actual size and shape of the benefited region.

Simulation approach to traffic noise modeling : American Automobile Manufacturers Association Community Noise Model version 4.0

Several models are available for predicting traffic noise levels. The FHWA-promulgated model, STAMINA 2.0, is the most widely used noise model in the United States and is used to model free-flow vehicular traffic. STAMINA 2.0 cannot directly model interrupted-flow traffic. Sound levels from interrupted-flow traffic can be approximated with STAMINA 2.0 using the method presented in NCHRP Report 311. This method is time-consuming and difficult to use. These limitations demonstrate the need for a traffic noise model that can model the acceleration and deceleration behavior of interrupted-flow traffic. The University of Central Florida has developed the American Automobile Manufacturers Association Community Noise Model (CNM). The CNM is a traffic simulation model that determines sound levels at receivers by modeling vehicles as discrete moving point sources. The vehicle energy is determined from acceleration, deceleration, idle, and cruise reference energy mean emission level curves. Sound energy attenuation is calculated from distance, ground absorption, and user input barriers. The model sums the energy at receivers from all vehicles and then calculates the Leq noise level at the receivers. It is demonstrated that the CNM predicts receiver Leq levels that are very close to STAMINA 2.0 results for constant-speed traffic. The CNM can also accurately predict sound levels at receivers located before and after intersections. In addition to the advantages of a real simulation model, the CNM is user friendly, allowing the user to place lanes and receivers using the mouse.

Understanding Airport Air Quality and Public Health Studies Related to Airports

This report provides airport industry stakeholders with an overview of what is known and not known regarding the impact of airport activity on air quality and public health. The report begins with a review of air quality standards and regulations. It then focuses on airport air quality issues, including source characteristics and emissions contributions, airport operations, geography, meteorology, mitigation measures, airport emissions and dispersion modeling, air quality measurement capabilities, and aircraft landing/takeoff emissions impacts vs. impacts at cruising altitude. The report then provides an overview of air quality health impacts and risk, followed by a discussion of the industry’s current understanding of airport air quality health impacts. The report concludes with recommendations for future research. Key features of the report include a summary of findings in the form of frequently asked questions and an extensive table summarizing the literature review.

Florida Noise Barrier Evaluation and Computer Model Validation

The results of a project that investigated the effectiveness of in situ noise barriers in Florida are presented. The prediction accuracy of the FHWA Traffic Noise Model (TNM) is compared with STAMINA 2.0 and 2.1 (Florida-specific). A total of 20 barrier sites were visited during a 3-year period that resulted in 844 discrete 20-min equivalent sound level (Leq) measurements behind the barriers. Barrier insertion loss was determined using the ANSI indirect barrier method. A methodology was developed to estimate shadow zone length created behind highway noise barriers. All of the barriers tested were effective (>5 dB:LAeq insertion loss at distances equivalent to the first row of homes, where LAeq is the A-weighted Leq) except one site because of marginal additional shielding from a berm–barrier combination. Only three sites had an insertion loss of less than 5 dB at distances representative of the second row of homes. Overall, measurements indicate that the barriers provide substantial sound level reduction for residents along the highway. TNM was the best prediction model when considering all test sites; however, the STAMINA models were more accurate at predicting source level. TNM predictions using the Average pavement input overpredicted the reference sound levels measured at these sites. TNM predictions using the OGAC (open-graded asphalt concrete) input were improved (under 2 dB:LAeq of error) over those using the Average pavement type input. This result is expected because Florida uses an open-graded asphalt friction mix.

QUEUEING ALGORITHM FOR CALCULATING IDLING EMISSIONS IN FLINT--THE FLORIDA INTERSECTION AIR QUALITY MODEL

The theoretical development of the queueing model used in the FLINT (FLorida INTersection) air quality model is described. FLINT is an area source model used to predict carbon monoxide concentrations for under-saturated and oversaturated traffic conditions at signalized intersections. In the FLINT model, deterministic queueing is used to estimate the queue length for cases of undersaturated conditions. In oversaturated cases, a cycle failure method has been developed to estimate queue length. In addition, a new concept is presented for calculating idling time for each vehicle’s position in the queue during both the red and the green phases of the traffic signal cycle. A limited set of undersaturated cases from monitoring data in Melrose Park, Illinois, was used to compare the predicted queue lengths with the measured queue lengths for several air quality models. It was found that FLINT predicted the queue length within one vehicle of the observed queue length. The same cases were tested using CAL3QHC, TEXIN2 intersection air quality models, and the American Automobile Manufacturers Association (AAMA) simulation model. It was found that predictions of the AAMA and the FLINT models were very close to the measured queue lengths in cases of undersaturated conditions. Moreover, although the FLINT and the AAMA models use a different approach to estimate queue length, their predicted queue lengths were very close in oversaturated cases. However, the predicted queue lengths of CAL3QHC were too long for oversaturated cases.

Guidance for Quantifying the Contribution of Airport Emissions to Local Air Quality

This report is a guide for airport operators on effective procedures for using air quality models in combination with on-site measurement equipment to prepare a comprehensive assessment of air pollutant concentrations in the vicinity of airports. It is designed to help practitioners generate information desired by local communities as they seek to develop more detailed local air quality assessments as well as respond to regulatory needs, including those of the National Environmental Policy Act (NEPA). The guide provides in-depth information on the capabilities and limitations of modeling and measurement tools, adding to an increasing knowledge base concerning preparation of air quality assessments near airports. Starting with the Federal Aviation Administrations (FAAs) regulatory EDMS/AEDT, it describes how best to use available models, in combination with potential on-site monitoring programs, to conduct air quality assessments. Detailed information on the monitoring campaigns and modeling assessments is included in a set of appendices that accompany the guide. The appendices (available in CRP-CD-115) describe the models tested and the various equipment used to collect data, the rationale behind the selection of Washington Dulles International Airport as a case study application, and the components and steps involved in the measurement campaigns, and include an assessment of the various model outputs.

Sound Levels and Shadow Zones Behind Barriers in Florida

A description is given of new results based on measurements of 19 noise barriers in the state of Florida and the innovative techniques used during data analysis. This work is a continuation of an ongoing study of noise barrier effectiveness in Florida. A new empirical method was developed to estimate the length of shadow zones behind highway noise barriers. This new method can lead to more effective design of future highway noise barriers. The method required an estimate of location and strength of a simulated background source to determine a more realistic edge of the shadow zone. This work also produced custom software that estimates and graphs the formation of shadow zones behind barriers, given readily available site information.

Method To Determine Reasonableness and Feasibility of Noise Abatement at Special Use Locations

Most states have policies in place that determine whether noise abatement is necessary and reasonable/feasible for Type I projects. These policies mirror federal guidance and apply to various land uses near the proposed project. Special land use facilities such as parks, churches, and schools are included in the policy as far as when abatement may be necessary (i.e., FHWA noise abatement criteria), but the determination of whether the abatement is reasonable or feasible may not be adequately addressed. A survey of state Departments of Transportation (DOTs) indicated that states are dealing with this need for reasonable/feasible determination for special land uses but do not have formal policies in place to address the issue. A systematic procedure would eliminate arbitrary decisions. A methodology developed for the Florida DOT to aid in the development of a procedure for special land use cases is presented. This methodology includes a feasibility flowchart that leads an individual through the process of determining whether abatement at a special land use site is feasible. The feasibility flowchart directs the individual to cease analysis because abatement is not feasible or to continue onto a reasonableness worksheet that determines whether abatement at the site is reasonable. The reasonableness worksheet leads the individual through site-specific calculations to derive an “abatement cost factor” used to determine reasonableness of abatement at the site.