bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of model schematisation, geometry and parameter values on urban flood modelling
Authors: Vojinovic Z. , Seyoum S. D. , Mwalwaka J. M. , Price R. K.
Published: February 2011

One-dimensional (1D) hydrodynamic models have been used as a standard industry practice for urban flood modelling work for many years. More recently, however, model formulations have included a 1D representation of the main channels and a 2D representation of the floodplains. Since the physical process of describing exchanges of flows with the floodplains can be represented in different ways, the predictive capability of different modelling approaches can also vary. The present paper explores effects of some of the issues that concern urban flood modelling work. Impacts from applying different model schematisation, geometry and parameter values were investigated. The study has mainly focussed on exploring how different Digital Terrain Model (DTM) resolution, presence of different features on DTM such as roads and building structures and different friction coefficients affect the simulation results. Practical implications of these issues are analysed and illustrated in a case study from St Maarten, N.A. The results from this study aim to provide users of numerical models with information that can be used in the analyses of flooding processes in urban areas.
Microbial community analysis in the autotrophic denitrification process using spent sulfidic caustic by denaturing gradient gel electrophoresis of PCR-amplified genes
Authors: Lee J. -H. , Lee S. -M. , Choi G. -C. , Park H. -S. , Kang D. -H. , Park J. -J.
Published: February 2011

Spent sulfidic caustic (SSC) produced from petrochemical plants contains a high concentration of hydrogen sulfide and alkalinity, and some almost non-biodegradable organic compounds such as benzene, toluene, ethylbenzene and xylenes (BTEX). SSC is mainly incinerated with auxiliary fuel, leading to secondary pollution problems. The reuse of this waste is becoming increasingly important from economic and environmental viewpoints. To denitrify wastewater with low COD/N ratio, additional carbon sources are required. Thus, autotrophic denitrification has attracted increasing attention. In this study, SSC was injected as an electron donor for sulfur-based autotrophic denitrification in the modified Ludzack-Ettinger (MLE) process. The efficiencies of nitrification, COD, and total nitrogen (TN) removal were evaluated with varying SSC dosage. Adequate SSC injection exhibited stable autotrophic denitrification. No BTEX were detected in the monitored BTEX concentrations of the effluent. To analyse the microbial community of the MLE process, PCR-DGGE based on 16 S rDNA with EUB primers, TD primers and nirK gene with nirK primers was performed in order to elucidate the application of the MLE process to SSC.
Development of a real-time RT-PCR assay combined with ethidium monoazide treatment for RNA viruses and its application to detect viral RNA after heat exposure
Authors: Kim K. , Katayama H. , Kitajima M. , Tohya Y. , Ohgaki S.
Published: February 2011

A method was developed for discriminating damaged viruses or naked viral RNA from intact viruses by ethidium monoazide (EMA) treatment before RT-PCR. The applied EMA treatment consisted of three steps: (1) EMA dose, (2) exposure to light, and (3) additional purification by spin-column gel filtration. Approximately 4-log reduction in viral RNA concentration was observed by adding a dose of 10 μg/mL-EMA with 300 s of light irradiation. Although residual EMA can be an inhibitor of RT-PCR, its effect was reduced by spin-column gel filtration or a QIAamp® Viral RNA Mini Kit. EMA-RT-PCR was applied to the thermally treated PV1. Results of EMA-RT-PCR were similar to the plaque assay when PV1 was thermally inactivated. Although this is a preliminary study investigating applicability of the EMA-RT-PCR method for RNA viruses, the results suggest that the method is potentially applicable for the selective detection of epidemiologically important enteric viruses in water such as enteroviruses and noroviruses.
Simulating organic pollutant flows in urban stormwater: development and evaluation of a model for nonylphenols and phthalates
Authors: Björklund K. , Malmqvist P. -A. , Strömvall A. -M.
Published: February 2011

Stormwater-quality models can be useful tools for predicting pollutant loads and identifying sources of contamination. Most models in current use handle pollutants such as metals, nutrients and suspended solids, whereas models including emerging organic contaminants are rare. This study aims at developing and evaluating a model for simulating stormwater flows of two groups of organic pollutants; nonylphenols and phthalates. Sources, emission patterns and environmental fate were examined to create a model framework for the organic contaminants. The model was calibrated using field data from three urban catchments. The results show that the simulated pollutant concentrations are overestimated compared to the measured concentrations, which are often close to or below the analytical detection limit. The high uncertainty and the low predictive power of the model may be explained by factors such as incorrect catchment data, lack of knowledge on buildup, washoff and other processes involved in substance fate, and an underreporting of pollutant concentrations in stormwater. More data on release patterns and sewer fate are needed to adequately simulate stormwater concentrations of nonylphenols and phthalates. A conventional substance flow analysis based on bookkeeping, evaluated in parallel to the computer model, has proven to be useful for calculating fluxes of nonylphenols and phthalates in urban catchments.
A practitioner’s perspective on the uses and future developments for wastewater treatment modelling
Authors: Daigger G. T.
Published: February 2011

The modern age of wastewater treatment modelling began with publication of the International Water Association (IWA) Activated Sludge Model (ASM) No.1 and has advanced significantly since. Models are schematic representations of systems that are useful for analysis to support decision-making. The most appropriate model for a particular application often incorporates only those components essential for the particular analyses to be performed (i.e. the simplest model possible). Characteristics of effective models are presented, along with how wastewater modelling is integrated into the wastewater project life cycle. The desirable characteristics of wastewater treatment modelling platforms are then reviewed. Current developments of note in wastewater treatment modelling practice include estimates of greenhouse gas emissions, incorporating uncertainty into wastewater modelling and design practice, more fundamental modelling of process chemistry, and improved understanding of the degradability of wastewater constituents in different environments. Areas requiring greater emphasis include increased use of metabolic modelling, characterisation of the hydrodynamics of suspended and biofilm biological treatment processes, and the integration of biofilm and suspended growth process modelling. Wastewater treatment models must also interface with water and wastewater management software packages. While wastewater treatment modelling will continue to advance and make important contributions to practice, it must be remembered that these are complex systems which exhibit counter-intuitive behaviour (results differ from initial expectations) and multiple dynamic steady-states which can abruptly transition from one to another.
Chemical monitoring strategy for the assessment of advanced water treatment plant performance
Authors: Drewes J. E. , McDonald J. A. , Trinh T. , Storey M. V. , Khan S. J.
Published: February 2011

A pilot-scale plant was employed to validate the performance of a proposed full-scale advanced water treatment plant (AWTP) in Sydney, Australia. The primary aim of this study was to develop a chemical monitoring program that can demonstrate proper plant operation resulting in the removal of priority chemical constituents in the product water. The feed water quality to the pilot plant was tertiary-treated effluent from a wastewater treatment plant. The unit processes of the AWTP were comprised of an integrated membrane system (ultrafiltration, reverse osmosis) followed by final chlorination generating a water quality that does not present a source of human or environmental health concern. The chemical monitoring program was undertaken over 6 weeks during pilot plant operation and involved the quantitative analysis of pharmaceuticals and personal care products, steroidal hormones, industrial chemicals, pesticides, N-nitrosamines and halomethanes. The first phase consisted of baseline monitoring of target compounds to quantify influent concentrations in feed waters to the plant. This was followed by a period of validation monitoring utilising indicator chemicals and surrogate measures suitable to assess proper process performance at various stages of the AWTP. This effort was supported by challenge testing experiments to further validate removal of a series of indicator chemicals by reverse osmosis. This pilot-scale study demonstrated a simplified analytical approach that can be employed to assure proper operation of advanced water treatment processes and the absence of trace organic chemicals.
Heat Transfer Enhancement of a Three Phase Circulating Fluidized Bed Fruit Juice Evaporator Using Inert Particles
Authors: Song Jitian , Chi Jun
Published: February 2011

In this paper, pumpkin juice concentration was carried out using a three-phase circulating fluidized bed evaporator. The flow and heat transfer characteristics of the evaporation process were investigated and parametric studies were conducted to identify the governing parameters in the process. It was found that the heat transfer efficiency was improved by 35 percent through addition of the inert particles into the two-phase evaporation process. Inert particles also inhibited the forming of fouling during the pumpkin juice concentration. A correlation equation of the boiling heat transfer coefficient was established for the three-phase circulating fluidized bed evaporator. This work improves the understanding of the three-phase circulating fluidized bed evaporator, which is beneficial to its wider application in the foodstuff processing field.
Investigation of the bioremediation potential of aerobic zymogenous microorganisms in soil for crude oil biodegradation
Authors: Solevic Tatjana , Novakovic Milan , Ilic Mila , Antic Malisa , Vrvic Miroslav , Jovancicevic Branimir
Published: February 2011

The bioremediation potential of the aerobic zymogenous microorganisms in soil
(Danube alluvium, Pancevo, Serbia) for crude oil biodegradation was
investigated. A mixture of paraffinic types of oils was used as the
substrate. The laboratory experiment of the simulated oil biodegradation
lasted 15, 30, 45, 60 and 75 days. In parallel, an experiment with a control
sample was conducted. Extracts were isolated from the samples with chloroform
in a separation funnel. From these extracts, the hydrocarbons were isolated
by column chromatography and analyzed by gas chromatography-mass spectrometry
(GC-MS). n-Alkanes, isoprenoids, phenanthrene and its derivatives with one
and two methyl groups were quantitatively analyzed. The ability and
efficiency of zymogenous microorganisms in soil for crude oil bioremediation
was assessed by comparison between the composition of samples which were
exposed to the microorganisms and the control sample. The investigated
microorganisms showed the highest bioremediation potential in the
biodegradation of n-alkanes and isoprenoids. A considerably high
bioremediation potential was confirmed in the biodegradation of phenanthrene
and methyl phenanthrenes. Low bioremediation potential of these
microorganisms was proven in the case of polycyclic alkanes of the sterane
and triterpane types and dimethyl phenanthrenes.
Empirical Derivation to Improve the Definition of the Metabolic Syndrome in the Evaluation of Cardiovascular Disease Risk
Authors: Wildman Rachel P. , McGinn Aileen P. , Kim Mimi , Muntner Paul , Wang Dan , Cohen Hillel W. , Ogorodnikova Alexandra D. , Reynolds Kristi , Fonseca Vivian
Published: February 2011

OBJECTIVE

To examine whether a quantitatively derived metabolic syndrome definition predicts incident cardiovascular disease (CVD) events better than do existing definitions.

RESEARCH DESIGN AND METHODS

Data were pooled from the Atherosclerosis Risk in Communities, Cardiovascular Health, and Framingham Offspring studies (n = 20,581). Incident coronary heart disease and stroke events were ascertained over 9 years.

RESULTS

The sensitivity for incident CVD events was higher and the specificity lower for the empirically derived versus the Adult Treatment Panel (ATP) III, International Diabetes Federation (IDF), or Harmonized metabolic syndrome definitions (sensitivity/specificity 0.65/0.53 vs. 0.53/0.63, 0.51/0.66, and 0.64/0.56, respectively), resulting in no overall improvement in discrimination. Multivariable-adjusted hazard ratios for incident CVD events were similar across definitions and were 1.7 (95% CI 1.6–1.9) for ATP III, 1.8 (1.6–2.0) for IDF, 1.9 (1.7–2.0) for Harmonized, and 1.7 (1.6–1.9) for the empirically derived definition.

CONCLUSIONS

Empirical derivation of the metabolic syndrome definition did not improve CVD discrimination or risk prediction.
Diagnosis of the Metabolic Syndrome Is Associated With Disproportionately High Levels of High-Sensitivity C-Reactive Protein in Non–Hispanic Black Adolescents
Authors: DeBoer Mark D. , Gurka Matthew J. , Sumner Anne E.
Published: February 2011

OBJECTIVE

Whereas it is known that the metabolic syndrome (MetS) has a paradoxically lower prevalence in non–Hispanic black adolescents than in non–Hispanic whites or Hispanics, the relative severity of MetS by race/ethnicity is unknown. Inflammation, indicated by high-sensitivity C-reactive protein (hsCRP), is a key factor linking MetS to cardiovascular disease and type 2 diabetes. Our goal was to determine whether elevations of hsCRP vary by race/ethnicity among adolescents with MetS.

RESEARCH DESIGN AND METHODS

We used the National Health and Nutrition Examination Survey (1999–2008) and evaluated adolescents (age 12–19 years) using a pediatric/adolescent adaptation of the ATP III definition of MetS. We used linear regression to evaluate the interaction between MetS status and ethnicity with respect to hsCRP concentration.

RESULTS

For male and female adolescents, MetS was associated with elevated hsCRP levels compared with adolescents without MetS. However, the elevation in hsCRP between adolescents with and without MetS was greater in non–Hispanic blacks compared with that in non–Hispanic whites (P = 0.04) but not that in Hispanics (P = 0.18). hsCRP concentrations correlated with individual MetS components similarly among all ethnicities. In an evaluation of adolescents diagnosed with MetS, non–Hispanic blacks had higher BMI and more hypertension than other ethnicities but there were no other racial/ethnic differences in the features of MetS.

CONCLUSIONS

Non–Hispanic black adolescents have a greater differential in hsCRP between those with and those without MetS than the differential in non–Hispanic whites but not that in Hispanics. Therefore, even though MetS has a low prevalence in non–Hispanic blacks, MetS is a particularly good indicator of inflammation in non–Hispanic black adolescents.
Urine C-Peptide Creatinine Ratio Is a Noninvasive Alternative to the Mixed-Meal Tolerance Test in Children and Adults With Type 1 Diabetes
Authors: Besser Rachel E.J. , Ludvigsson Johnny , Jones Angus G. , McDonald Timothy J. , Shields Beverley M. , Knight Bridget A. , Hattersley Andrew T.
Published: February 2011

OBJECTIVE

Stimulated serum C-peptide (sCP) during a mixed-meal tolerance test (MMTT) is the gold standard measure of endogenous insulin secretion, but practical issues limit its use. We assessed urine C-peptide creatinine ratio (UCPCR) as an alternative.

RESEARCH DESIGN AND METHODS

Seventy-two type 1 diabetic patients (age of diagnosis median 14 years [interquartile range 10–22]; diabetes duration 6.5 [2.3–32.7]) had an MMTT. sCP was collected at 90 min. Urine for UCPCR was collected at 120 min and following a home evening meal.

RESULTS

MMTT 120-min UCPCR was highly correlated to 90-min sCP (r = 0.97; P < 0.0001). UCPCR ≥0.53 nmol/mmol had 94% sensitivity/100% specificity for significant endogenous insulin secretion (90-min sCP ≥0.2 nmol/L). The 120-min postprandial evening meal UCPCR was highly correlated to 90-min sCP (r = 0.91; P < 0.0001). UCPCR ≥0.37 nmol/mmol had 84% sensitivity/97% specificity for sCP ≥0.2 nmol/L.

CONCLUSIONS

UCPCR testing is a sensitive and specific method for detecting insulin secretion. UCPCR may be a practical alternative to serum C-peptide testing, avoiding the need for inpatient investigation.
When Technology Tells Novice Drivers how to Drive
Authors: Musicant Oren , Lampel Liat
Published: February 2011

The usefulness of feedback from technology to moderate risky behavior of young novice drivers was studied in a before-and-after experiment. Thirty-two vehicles were fitted with a device designed to identify occurrences of unsafe driving events (e.g., sharp turns, excessive braking and accelerating, swift lane changing) by young novice drivers. The event frequency (EF) in more than 18,000 trips was analyzed with mixed effect regression models with Poisson errors and several graphical methods. Results indicated a reduction in EF of more than 50% when feedback was available. These results suggested that feedback from technology could reduce risky behavior by young novice drivers.
Law Enforcement Vehicle Crashes in Florida
Authors: Carrick Grady , Srinivasan Siva , Washburn Scott S.
Published: February 2011

This study analyzed 31,438 reported crashes that involved 33,638 law enforcement vehicles, 27,723 non–law enforcement vehicles, 463 pedestrians, and 391 bicyclists that occurred in Florida from 2005 through 2008. These crashes resulted in more than $101 million in total damages, 10,124 injuries, and 88 fatalities. The law enforcement vehicle crashes could be characterized by descriptive techniques such as frequencies analysis and cross-tabulation. This study found that the typical law enforcement crash was a low-speed event on a local street. Stop and signalized intersection locations were well represented in the data. The law enforcement vehicle commonly moved straight, slowed, and stopped or was parked when it crashed. Rear-end and backing-type crashes were common. Most crashes occurred during the daytime, under favorable driving conditions, and during routine operating mode. Most of the time, the driver of the law enforcement vehicle did not contribute to the cause of the collision, and the vast majority of crashes did not result in any injury. Typically, law enforcement vehicles were driven away from the scene of the collision, and total damages averaged slightly more than $3,000. Pursuit and emergency operation mode crashes made up about 23% of the crashes. In these operating conditions, vehicle speed, injury severity, and damages all increased, although the culpability of the law enforcement vehicle operator usually did not. The environmental conditions for emergency mode were not significantly different than for other crashes.
Exploring Travel Characteristics and Factors Affecting the Degree of Willingness of Seniors in Taiwan to Use an Alternative Service Bus
Authors: Chen Wan-Hui
Published: February 2011

This study investigated the travel characteristics of seniors in Taiwan through the use of a questionnaire survey. Survey results revealed that walking was the travel mode used to participate in the three most popular activities among seniors: doing outdoor exercise, chatting with neighbors, and shopping. For an aging society, a safe and barrier-free walking environment was an essential transportation requirement. Access to a transit system with frequent bus service could help ensure participation by elderly citizens in activities at greater distances from their homes. In areas where bus service was infrequent, a demand-responsive service (DRS) bus could serve as an alternative means of transportation for older adults. This study examined factors that contributed to the degree of willingness of elderly subjects to use a DRS bus for their medical trips. The influential factors included age, education, eye and bone problems, transportation mode typically used for medical trips, distance to the closest hospital or clinic, walking distance to the nearest bus stop, and bus frequency. This study suggested that the following areas should have the highest priority for a DRS bus system: areas located 20 min or more from the nearest hospital or clinic, areas located 10 min or more from the nearest bus stop, and areas where bus service is infrequent.
Development of a Kilometer-Based Rewards System to Encourage Safer Driving Practices
Authors: Greaves Stephen , Fifer Simon
Published: February 2011

Interest is growing in the use of kilometer-based financial mechanisms to encourage safer driving practices and reduce accident claims. The rationale behind such an approach is that, in addition to driver characteristics such as age and gender, crash risk is intrinsically a function of both the kilometers driven and the circumstances under which those kilometers are driven (e.g., time of day, day of week, road type, speed). Using recent accident data and travel survey data collected in the Sydney, Australia, greater metropolitan area, options were explored to design a kilometer-based reward scheme that incentivized drivers to reduce their kilometers traveled, nighttime driving, and speeding. Results show that young drivers (17 to 30 years old) would be hardest hit by the proposed scheme, and middle-aged drivers (31 to 65) would fare best. The impacts of the rewards system were assessed hypothetically by using evidence from 125 motorists who completed 5 weeks of driving in which their kilometers traveled, nighttime driving, and speeds were monitored with the latest Global Positioning System technology. Various charging scenarios and hypothesized behavioral changes were implemented to assess both their incentive for change and the overall financial impact of the project. These results were used in conjunction with the theoretical and empirical justification outlined in this paper to set the final charging regime rates on the basis of the overall study budget.
Review of State Roundabout Programs
Authors: Pochowski Alek , Myers Edward J.
Published: February 2011

As the modern roundabout continues to grow in popularity in the United States, more states are considering or implementing statewide roundabout programs. To assist states in implementing statewide roundabout programs, a review of four such programs was conducted in Kansas, Maryland, New York, and Wisconsin. The review was completed through an examination of published state roundabout guides and interviews. Results from the review indicate that agency buy-in, public perception, and establishment of a statewide roundabout policy all play crucial roles in the success or failure of a statewide roundabout program. It is recommended, therefore, that agencies focus on these areas to ensure success in establishing a roundabout program statewide.
Roundabouts in Signalized Corridors
Authors: Hallmark Shauna L. , Fitzsimmons Eric J. , Isebrands Hillary N. , Giese Karen L.
Published: February 2011

Typically, roundabouts in the United States are installed at isolated intersections to address location-specific safety or operational needs. The use of roundabouts in signalized corridors, however, has not been well evaluated. It is commonly believed that roundabouts can improve traffic flow and travel speeds along an urban corridor by reducing delay caused by idling at intersections. Concern exists, however, that a roundabout in a coordinated signalized corridor will disrupt continuous traffic flow: downstream signals can more efficiently process vehicles in a platoon, and roundabouts disperse rather than form platoons. Roundabouts also can discharge vehicles more efficiently when traffic arrives randomly. Thus unnecessary queuing may result when roundabouts are downstream of signalized intersections. Since little research was available to compare the traffic flow impacts of roundabouts within a signalized corridor, two case studies were evaluated with the microscopic traffic simulation package, VISSIM. A roundabout and two signalized alternatives, as well as a roundabout and a four-way, stop-controlled alternative, were compared at intersections along signalized corridors in Ames, Iowa, and Woodbury, Minnesota, respectively. The traffic data and corridor geometry were coded into VISSIM, and traditional intersection traffic control within the corridors was compared with a scenario that had a two-lane roundabout. With the microsimulation software, average travel time, stopped delay, and average delay for the entire corridor were compared.
Impact of Network Improvement on Revenue Performance and Bonding Costs of Toll Roads
Authors: Vajdic Nevena , Damnjanovic Ivan , Suescun David R. , Waller S. Travis
Published: February 2011

Increased interest in new and alternative methods for delivering projects places special emphasis on agreements for public–private partnerships. In such arrangements, the public sector must conform to a set of contractual obligations and also is responsible for long-term planning of the transportation network and for providing a better service on the existing public infrastructure. In this context, any changes in the initial network structure represent an additional risk element, acting as an externality to the toll road developer. This paper examines the impact of these changes on the price of selected risk measures (that is, the price of the revenue risk minus the cost of debt). An analytical method is developed that relates network improvement decisions to credit risk measures. The method is applied to two networks to examine the behavior of the credit spread when changes occur in the capacities on feeder and competing links. Sensitivity analyses show that a decrease in the capacity on feeder links might have a higher (adverse) impact on the credit spread than an increase in the capacity on competing links.
Flexible-Term Highway Concessions
Authors: Vassallo José Manuel
Published: February 2011

Highway concessions are becoming popular around the world. One of the main issues in adequately designing concession contracts is how best to allocate traffic risk. Many concession contracts, therefore, are incorporating traffic risk mitigation mechanisms to limit the amount of traffic risk ultimately taken on by the concessionaire. One of the most interesting approaches in the mitigation of traffic risk is the design of flexible-term concessions (FTCs) that end automatically when a certain level of accumulated traffic or revenues is reached. The concession duration may be extended if real traffic becomes lower than expected and shortened when real traffic is higher than expected. The aim of this paper is to survey and assess the implementation of FTCs to explore why these mechanisms have so seldom been adopted. The author found that the main reason for the scarce implementation of these mechanisms lies in the strong opposition of the private sector to FTCs because of the asymmetric risk profile that FTCs present. This risk profile means that the potential gains for the concessionaire are substantially limited, while potential losses are not limited to nearly the same degree. The paper ends with some recommendations for improving the acceptability of FTCs.
Quantitative Analysis of Impacts of Moving toward a Vehicle Mileage-Based User Fee
Authors: Sana Bhargava , Konduri Karthik C. , Pendyala Ram M.
Published: February 2011

This paper offers a broad examination of the revenue generation and social equity implications of a national mileage-based user fee that could be substituted for all or part of the current gas tax. Data from the 2001 National Household Travel Survey are combined with documented elasticity values that can be used to calculate changes in vehicle fleet composition and miles of travel by time of day in response to price signals. These data provide the basis for calculating the impacts of a mileage-based user fee system. It is found that modest mileage-based fees of just 0.5 cent per mile to 1.3 cents per mile can offer revenue streams that replace current gas tax revenue. In addition, the mileage-based user fee system appears to have minimal, if any, differential impacts across income classes and thus eliminates any potential equity concerns that may arise from the implementation of such a user fee system. Impediments to a mileage-based user fee system appear likely to be technological and personal privacy issues as opposed to transportation or social equity issues.
Consideration of Congestion Pricing and Managed Lanes in Metropolitan Transportation Planning
Authors: Loudon William R. , Synn Jienki , Miller Harlan
Published: February 2011

Under FHWA sponsorship, DKS Associates conducted a national scan of how agencies in major metropolitan areas are developing plans for congestion pricing, managed lanes, or both. Staff members from the metropolitan planning organization (MPO) and the state department of transportation (DOT) in 10 metropolitan areas were surveyed to find out how they are including consideration of congestion pricing, managed lanes, or both in their metropolitan planning processes and the development of long-range transportation plans for the region. In addition, the study team identified projects already in operation in each region, those already in the long-range plan, and those being considered. The study results reported in this paper focused on how the MPOs, state DOTs, and other key agencies interact, contribute, and cooperate in considering congestion pricing or managed lanes. The study also produced information on methods used to evaluate these strategies, including modeling tools used, performance measures used, and how network effects, diversion of trips, and equity effects are taken into account. The study identified how federal grants were used to fund studies and projects in the early stages of consideration of congestion pricing or managed lanes in the 10 regions. Public and stakeholder involvement methods used by the MPOs and state DOTs to advance projects were also identified.
Congestion Pricing on Highways in Chicago, Illinois
Authors: Greene Elizabeth R. , Smith Colin
Published: February 2011

Traffic congestion causes losses of $7.3 billion per year in the six-county Chicago, Illinois, area. Many efforts are under way to improve existing infrastructure and manage travel demand to reduce the burdens of congestion. In 2008, the Chicago Travel Options Study, a stated preference survey, was conducted to assess whether two types of road pricing would manage travel demand. The survey employed a split sample approach: half of the respondents completed stated preference experiments that tested the likelihood of using managed lanes on Chicago area highways, and the other half completed experiments that tested peak period toll increases. The paper finds that Chicago travelers appear to favor managed lanes over increasing or placing tolls on toll-ways and expressways. The survey asked a set of questions to gauge attitudes toward tolling, public transit, and environmental concerns. The paper examines how individuals' opinions on these three topics vary by demographics and trip characteristics and presents the results of a K-means cluster analysis that shows that around 20% of the respondents have a strong willingness to pay tolls and to change their behavior to benefit transit and the environment. A group of respondents similar in size is open to managed lanes as a means to reduce congestion but is less likely to change behavior for environmental reasons. The paper benchmarks Chicago area travelers' opinions against those of travelers from other parts of the United States and shows that they have a higher willingness to pay tolls and to use toll roads but have similar environmental attitudes.
Freight and Passenger Modeling Using Hybrid Econometric–Network Models
Authors: Vilain Pierre B. , Muhammad Talha , Li Cathleen , Hallissey Matt
Published: February 2011

The experience of the past several years for toll roads in the Americas and Europe has been sobering, with generalized declines in traffic after years of consistent growth. The twin effects of high fuel prices and economic recession have resulted in year-over-year traffic declines for some facilities of well over 10% and in some instances as much as 20%. Analysis suggests that the focus of passenger and freight traffic modeling needs to include the impact of economic variables more comprehensively, because this area is responsible for substantial variability and economic risk to a project's financial returns. This risk is greater in the case of freight traffic, which is more prone to economic cycles than passenger traffic. This paper describes an approach that incorporates both econometric models (which explicitly model the relationship between economic variables and traffic) and network models (which account for changes in the network and relative congestion on alternative routes). The paper illustrates several examples of mature facilities for which the risk from economic uncertainty far outweighs the risk from network changes. The principal focus of the paper is a description of how network and econometric models can be combined into a single model, with an assessment of how this combination results in improved forecasting tools. Case studies are included to outline the settings to which combined models are most readily applied, and calibration results are reported to illustrate the soundness of the approach.
Tale of Two Ecosuburbs in Freiburg, Germany
Authors: Broaddus Andrea
Published: February 2011

This paper compares two ecosuburbs of Freiburg, Germany, created over the past 10 years and similar in many respects except for provision of parking. Both are transit-oriented developments designed as family-friendly live–work–play places, composed of mixed-use commercial and residential buildings meeting ecological best practices. Both suburbs have similar high density, are located about 3 km from the city center, and have excellent transit and bicycling connections. Rieselfeld followed the German convention of one parking spot per residence, while Vauban was designed by environmentalist citizen–activists to support car-free living. Parking cost and location were unbundled from housing, with parking spots provided at construction cost in garages on the periphery of the Vauban district. Demand was strong for this pedestrian- and bicycle-oriented housing, and residents used these modes at a higher rate. Fewer households in Vauban owned cars, and car-owning households were observed to drive less often. Travel behavior data showed that residents of Rieselfeld had higher rates of transit use in an otherwise typical modal split, while Vauban's residents had an extremely low share of cars and a high share of bicycles. These differences were attributed in part to Vauban's more restrictive parking policies.
Markets for Dynamic Ridesharing?
Authors: Deakin Elizabeth , Frick Karen Trapenberg , Shively Kevin M.
Published: February 2011

Ridesharing programs are widespread across the United States. Dynamic ridesharing is a newer way to share rides on the fly or up to several days in advance using cell phone or computer messaging to make arrangements. This paper describes research conducted to assess the potential for dynamic ridesharing for travel to downtown Berkeley, California, and the University of California, Berkeley, campus. The study provides insights about the opportunities and challenges presented by this travel option. Data were collected from statistical and geographic analysis of the downtown and campus travel markets, and surveys and focus groups were administered to employees and graduate students. The study found that about one-fifth of commuters who drive alone to the campus would be interested in using dynamic ridesharing at least occasionally and live in areas where matches could be found. They would prefer to arrange a shared ride at least the night before rather than immediately before the trip is made. Many of these travelers were unaware of current rideshare services, and some would be willing to find a regular carpool partner. Finally, if parking charges are fairly high and parking supply is limited and regulated, financial incentives and carpool parking subsidies greatly increase interest in dynamic ridesharing.
Carsharing Parking Policy
Authors: Shaheen Susan A. , Cohen Adam P. , Martin Elliot
Published: February 2011

Carsharing provides users access to a shared vehicle fleet for short-term use throughout the day, reducing the need for private vehicles. The provision of on-street and public off-street parking dedicated to carsharing is an important policy area confronting public agencies. As of July 2009, approximately 377,600 individuals were carsharing members in North America in about 57 metropolitan areas. Seventeen jurisdictions, one state (California), and eight public transit operators in North America have formal and informal carsharing parking policies, pilot projects, and proposed legislation. These policies, projects, and proposals are reviewed in this paper, along with a framework for carsharing parking policy that reflects three levels of government support. In addition, the authors examine carsharing parking policies in three jurisdictions in the San Francisco Bay Area in California that account for an estimated 50,000 carsharing members and 1,100 shared-use vehicles. Supporting this examination is an intercept survey on carsharing parking (n = 425) conducted in the Bay Area. Most people supported the conversion of some type of spaces for carsharing use, and 48% thought that carsharing organizations should compensate the city for on-street spaces. At the same time, converting most types of spaces was opposed by at least 20% of respondents. Neighborhood residents were generally more in favor of parking conversion for carsharing than people visiting the area for work or errands. Finally, a majority (61%) thought that nonprofits should have priority over for-profit organizations for carsharing spaces and should pay less than for-profit organizations.
Mesoscopic Modeling of Bus Public Transportation
Authors: Cats Oded , Burghout Wilco , Toledo Tomer , Koutsopoulos Haris N.
Published: February 2011

Analysis of public transport system performance and level of service in urban areas is essential. Dynamic modeling of traffic conditions, passenger demand, and transit operations is important to represent adequately the complexity of and the interactions between these components in modern public transportation systems. This paper presents a transit simulation model designed to support evaluation of operations planning and control, especially in the context of advanced public transportation systems. Unlike most previous efforts in this area, the simulation model is built on a platform of a mesoscopic traffic simulation model, which allows modeling of the operation dynamics of large-scale transit systems, taking into account the main sources of service uncertainty and stochasticity. The capabilities of Mezzo as an evaluation tool of transit operations are demonstrated with an application to a real-world, high-demand bus line in metropolitan Tel Aviv, Israel, under various scenarios. The application shows that important phenomena such as bus bunching are reproduced realistically. A comparison of simulated running times and headway distributions with field data shows the model is capable of replicating observed data.
Mental Workload, Longitudinal Driving Behavior, and Adequacy of Car-Following Models for Incidents in Other Driving Lane
Authors: Hoogendoorn Raymond , Hoogendoorn Serge P. , Brookhuis Karel , Daamen Winnie
Published: February 2011

The values on parameters describing longitudinal driving behavior in car-following models differ substantially between drivers. Different individual interactions with the environment are assumed to play an important role, which might be explained through mental workload. Therefore a driving simulator experiment with a repeated measures design was performed to investigate to what extent perception of an incident in the other driving lane influences physiological indicators as well as subjective estimates of mental workload and longitudinal driving behavior. As almost none of the current models of car-following behavior incorporate mental workload as a determinant of driving behavior, an investigation was conducted by using a calibration approach for joint estimation to determine whether these models, represented by the intelligent driver model and the Helly model, adequately described longitudinal driving behavior in case of incidents in the other driving lane. The results indicated that perception of an incident in the other driving lane influenced mental workload as measured by physiological indicators and longitudinal driving behavior. In addition, the results indicated that current car-following models did not adequately describe driving behavior in case of incidents in the other driving lane.
Calibration Issues for Multistate Model of Travel Time Reliability
Authors: Park Sangjun , Rakha Hesham , Guo Feng
Published: February 2011

Travel time reliability has received much attention from researchers and practitioners because it not only affects driver route choice behavior but also is used in the assessment of transportation system performance. Current state-of-the-art travel time reliability research assumes that roadway travel times follow a unimodal distribution. Specifically, a Weibull, exponential, lognormal, or normal distribution is used within the context of travel time reliability modeling. However, field observations demonstrate that roadway travel times are multimodal, especially during peak periods. This paper demonstrates that the multimodes observed in field data are a result of temporal variations in travel times both between and within days. This study evaluates the potential for generating multimodal travel times by using INTEGRATION software and investigates the underlying traffic states that result in these multimodes. The study validates the two-state model proposed in an earlier study and demonstrates the robustness of model parameter estimates under varying stochastic traffic congestion levels and sampling techniques.
Using Trajectory Data to Analyze Intradriver Heterogeneity in Car-Following
Authors: Wang Hao , Wang Wei , Chen Jun , Jing Ming
Published: February 2011

This paper presents a methodology for using vehicle trajectory data to study the intradriver heterogeneity of driving behavior between the acceleration process and the deceleration process. Trajectory data were collected during peak hours on Dutch Motorway A2. Criteria were proposed for the selection of subtrajectories corresponding to both the acceleration and the deceleration processes of car-following. With the application of these subtrajectories to calibrate three types of models (the Helly model, the Gipps model, and the intelligent driver model), it was found that obvious intradriver heterogeneities existed in driving behaviors between the acceleration and deceleration processes of car-following: (a) the average response time of drivers in the acceleration process was longer than that in the deceleration process according to the prediction of the Helly and intelligent driver models; (b) drivers were apt to respond more intensively to surrounding traffic in the deceleration process than they did in the acceleration process; and (c) more than 65% of drivers involved in this study drove in obviously different styles between the acceleration and deceleration processes. Moreover, a compensation for the response delay from model parameters was observed, and all three models presented low robustness in predicting driving behaviors of one car-following process with the parameters optimized from the data of other car-following processes. This work not only provides insight into intradriver heterogeneity in car-following behaviors but also suggests some important criteria for car-following modeling.
Onset of Congestion from Low-Speed Merging Maneuvers within Free-Flow Traffic Stream
Authors: Duret Aurélien , Bouffier Jacques , Buisson Christine
Published: February 2011

Low-speed merging maneuvers performed within a free-flow stream are believed to trigger congestion. These accelerating moving bottlenecks introduce local constraints that can disturb the flow at a local or global scale. Low-speed merging maneuvers are also suspected to cause capacity drop. Using the kinematic wave theory, this paper explores the analytical solution of a simple first-order model when moving boundary conditions are introduced. The paper shows that shock waves initiated by low-speed merging maneuvers are a linear transformation of the moving boundary conditions, no matter the shape of the moving boundary condition. These results are then applied to typical situations to show that the interaction of two moving boundaries can modify the analytical solution of the problem. The results are then extended to multiple merging maneuvers to show that they can interact. Every possible interaction between two identical merging maneuvers is explored to identify the conditions that lead to global congestion. Finally, these results are used to propose an analytical formulation of the capacity drop for multiple merging maneuvers at a single location. It is shown that capacity drop is related to the demands on the minor and major streams and to the speed of the merging vehicle.
Adaptive Estimation of Noise Covariance Matrices in Unscented Kalman Filter for Multiclass Traffic Flow Model
Authors: Ngoduy Dong , Sumalee Agachai
Published: February 2011

Traffic state estimation problems must deal with imperfect information. Imperfect information may occur as a result of misalignments between reality and the assumptions or simplifications made when developing the models as well as incomplete or corrupted data. One of the well-known methods of handling imperfect information is the Kalman filter algorithm and its variations, such as the extended Kalman filter and the unscented Kalman filter. While the standard Kalman filter and the extended Kalman filter have been widely applied to the state estimation of linear systems, the unscented Kalman filter has been reported the better choice in the multiclass traffic state estimation. In many applications of Kalman filters to traffic estimation problems, the model and measurement noise covariance matrices are normally estimated. When there is a mismatch between the true and the assumed noise distribution, however, the filter often suffers from performance degradation and even divergence in certain situations. To this end, this paper presents a more efficient and accurate algorithm embedded in the unscented Kalman filter to simultaneously estimate the traffic state and the model noise distribution statistics. The proposed method is facilitated through a simultaneous update of the model noise covariance matrix in the predicted covariance equations of the unscented Kalman filter algorithm. It is found through simulation that the proposed algorithm may improve the model performance over the standard algorithm.