bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Travel Demand Microsimulation Model for Equity Analysis
Authors: Castiglione Joe , Hiatt Rachel , Chang Tilly , Charlton Billy
Published: May 2018

This paper describes the application of a state-of-the-art, tour-based travel demand microsimulation model to estimate impact on mobility and accessibility on different populations to support development of a countywide transportation plan. Equity analyses based on traditional travel demand forecast models are compromised by aggregation biases and data availability limitations. Use of the disaggregate (individual person-level) San Francisco, California, tour-based microsimulation model made it possible to estimate benefits to and impact on different communities of concern on the basis of individual characteristics, such as gender, income, automobile availability, and household structure. The concepts and policy context of equity analysis in transportation are presented. Identifying communities of concern and relevant measures of transportation system performance are outlined. The San Francisco model structure is described, and the results of the equity analysis are presented.
Fitting Distributions to Random Parameters
Authors: Hollander Yaron
Published: May 2018

This research investigated the choice of distributions for the parameters of a mixed logit model, under the risk that the model appears statistically successful when its actual fit to the true behavior is poor. A subsampling technique is used to examine the aptitude of several model specifications to approximate the range of preferences of bus commuters in York, England. Difficulties in replicating the distribution of the willingness to pay are discussed. Various issues are raised, such as the existence of negative willingness to pay, constraining distributions by either estimation or imposition, and the potential of subsampling experiments.
Nonlinearity of Response to Level-of-Service Variables in Travel Mode Choice Models
Authors: Pinjari Abdul Rawoof , Bhat Chandra
Published: May 2018

It is important to accommodate variations in responsiveness (or response heterogeneity) to level-of-service (LOS) attributes in travel mode choice models. This response heterogeneity may be disaggregated into a systematic (observed) component and a random (unobserved) component. Earlier studies typically considered systematic response heterogeneity by examining differences in LOS response sensitivities caused by individual demographic and other attributes. The emphasis of the presented research is on another element of systematic response heterogeneity: that originating from nonlinear responsiveness to LOS attributes. Specifically, both the components of systematic response heterogeneity (due to individual characteristics and nonlinear responsiveness) as well as unobserved response heterogeneity are considered at the same time, and the empirical results of models that assume a traditional linear responsiveness to LOS attributes are compared with those that adopt a nonlinear responsiveness to LOS attributes. The empirical analysis uses data from the Austin commuter stated preference survey to examine commute travel mode choice. The nonlinear specifications for travel time and travel time unreliability indicate that in the first 15 min commuters place little value on travel time and high value on travel time reliability. Beyond 15 min, however, the valuation of travel time increases rapidly, whereas that of travel time reliability drops dramatically. In addition to clearly indicating the nonlinear nature of responsiveness to travel time and travel time unreliability, the results indicate that ignoring nonlinear responsiveness leads, in the current empirical context, to ( a) biased parameter estimates, ( b) an inflated estimate of unobserved heterogeneity, ( c) counterintuitive signs on the LOS variables for a high fraction of individuals, ( d) inaccurate estimates of willingness-to-pay measures, and ( e) loss in model fit.
Simulating Land use Development through a Stochastic Allocation Procedure in Johannesburg, South Africa
Authors: Venter Christoffel J. , Lamprecht Theuns , Badenhorst Willem
Published: May 2018

This paper describes a method of forecasting demographic and economic change at a spatially disaggregate level that is compatible with the requirements of a conventional transport model. The method was developed and tested in the city of Johannesburg, South Africa, as part of a scenario-planning exercise to assess potential land use and transport interventions. The procedure does not model land use development decisions explicitly but uses a geographic information system–based multi-criteria analysis approach incorporating the factors influencing the development of residential and nonresidential land uses, the constraints of land availability, and the guiding effects of government policy. Allocation occurs in discrete time steps, allowing the dynamic evolution of outcomes to be modeled in a nonequilibrium framework. It operates in connected mode with the transport model, taking accessibility changes as input into subsequent land use allocations. Monte Carlo simulation is used to approximate randomness in the location decision outcome, thus providing some sense of the variability of the outcomes that may occur at a zonal level. The method is illustrated for the city of Johannesburg for a 30-year planning horizon. It is shown to be particularly useful in developing societies where data to establish more elaborate behavioral models are absent or too costly to collect.
Location Choice vis-à-vis Transportation
Authors: Bina Michelle , Warburg Valdemar , Kockelman Kara M.
Published: May 2018

An understanding of residential location choice is fundamental to behavioral models of land use and, ultimately, travel demand. Detailed data and predictive models are needed. This research examined choices of apartment dwellers and their reasons for moving, their priorities when choosing a residential location, and the trade-offs involved. In addition to summary statistics of the data, linear regressions, binary logit, and ordered probit models were used to investigate variations in rent and apartment size and stated preferences of housing, location, transportation, and access. Binary logit and ordered probit models reveal similar results concerning people's preferences for accessibility. For instance, families and other multiperson households tend to place less value on commute times and freeway access and choose apartment improvements over travel savings. Women are more likely to state that they place a higher importance on commute time and freeway access, but, when asked to choose between travel times and apartment size, they are more likely to choose the larger apartment. Other models suggest that being within walking distance of a commercial center increases average rent by $24 per month. Increases in distances to the central business district (CBD) and mean neighborhood commute times reflect lower monthly rents, about $20 per mile from the CBD and $24 per added minute of commute (one way). Apartments in the urban area tend to be, on average, 75 ft2 smaller, all things being equal (including population density, which has an added effect). These results and many others provide several valuable insights regarding the location choice of those residing in apartments.
Nonstationary Spatial Interpolation Method for Urban Model Development
Authors: Vichiensan Varameth , Páez Antonio , Kawai Kenji , Miyamoto Kazuaki
Published: May 2018

In some situations in urban modeling practice, data cannot be preserved at the highest possible level of resolution. For example, when data from different sources are collated, the areal partitioning systems may not be compatible with each other. In other cases, related but separated models (e.g., urban transportation–land use and environmental models) may have been designed to operate at different spatial scales, posing a challenge to any efforts to link them. In these and similar situations, a method for interpolating data is required to produce compatible zoning systems or data at a desired level of resolution. A nonstationary (location-specific) spatial interpolation method, which has various potential applications in transportation as well as urban modeling, is proposed. The method combines the concept of location-specific parameters of a geographically weighted regression model and the concept of variogram function of kriging used to model spatial autocorrelation. Two case studies are presented to illustrate the application of the method in situations that are common in urban and transportation analysis. The results suggest that the method can be a useful alternative for spatial interpolation when nonstationarity and spatial autocorrelation appear co-incidentally in the analysis. The model is therefore expected to help to improve the performance of urban models by providing more accurate data at desired levels of resolution.
Tracking Land Cover Change in Mixed Logit Model
Authors: Wang Xiaokun , Kockelman Kara M.
Published: May 2018

As an essential part of integrated land use–transport models, prediction of land cover changes and illumination of the many factors behind such change are always of interest to planners, policy makers, developers, and others. A mixed logit framework is used to study land cover evolution in the Austin, Texas, region, recognizing distance-dependent correlations–-both observed and unobserved–-over space and time, in a sea of satellite image pixels. The computational methods used for model estimation and application are described, including generalized Cholesky decomposition and likelihood simulation. Results indicate that neighborhood characteristics have strong effects on land cover evolution: clustering is significant over time, but high residential densities can impede future development. Model application produces graphic predictions, allowing one to confirm these results visually and appreciate the variability in potential urban futures.
Probit-Type Reliability-Based Transit Network Assignment
Authors: Yang Liu , Lam William H. K.
Published: May 2018

This paper proposes a new probit-type reliability-based transit assignment model in a congested network with unreliable transit services. A new disutility function is developed to model the passenger route choice behavior under unreliable conditions; passengers will make a trade-off between the transit service reliability and the expected travel time for their route choice. In the proposed model, the total transit passenger demand is fixed, but the in-vehicle travel times by transit routes are formulated stochastically because of unreliable traffic conditions, particularly for buses on the road network. The effects of congestion on transit networks, such as elastic transit line frequencies and passenger overload delays, are also considered in the proposed model. A numerical example is provided to illustrate the applications of the proposed model and solution algorithm. It is shown that the traditional probit-type stochastic user equilibrium transit assignment is a special case of the proposed model. The findings also reveal the distribution of passenger waiting times and their overload delays at congested transit stations.
Parking at Mixed-Use Centers in Small Cities
Authors: Marshall Wesley E. , Garrick Norman W.
Published: May 2018

The debate about parking has shifted in the past decade, as some places attempt to move from conventional development patterns to urban centers modeled on new urbanism and smart growth concepts. There is now less focus on providing sufficient parking to meet demand and more on ensuring that the issue of parking does not undermine the creation of vibrant places. The goal for the presented project is to understand parking and parking provision better as it relates to smaller cities and towns with mixed-use centers. Specifically addressed are how a dense, walkable, mixed-use center affects parking supply and demand and how mixed-use centers compare with centers designed along more conventional lines. These questions were addressed by conducting case study assessments of six sites in New England. In general, the three mixed-use study sites provided much less parking per square foot than the conventional control sites. The study sites thrived by making much more efficient use of land for parking. The study sites also furnished a significant amount of on-street parking and relied more on shared municipal parking lots and parking garages. Given these differences, it is surprising to note that the towns with mixed-use centers demanded almost as much parking for new construction as did the towns in which the conventional sites are located. On average, the amount of parking mandated by base regulation in these six towns is about two and a half times greater than the peak use.
Influence of Transportation Access on Individual Firm Location Decisions
Authors: Targa Felipe , Clifton Kelly J. , Mahmassani Hani S.
Published: May 2018

Several studies of transportation and economic development impact have recognized the extent to which transportation investments may improve access to markets and, by doing so, influence firms’ location decisions. A study specified and empirically tested a firm-level model that captures the relationship between the propensity of a particular firm to relocate from its current business location as a function of local and regional accessibility, agglomeration economies, firm-specific characteristics, business-specific activity attributes, attitudes toward regional considerations, and factors that influenced the initial business location decision. The geographic area of analysis considers a four-county region in Maryland. The econometric analysis establishes significant association between transportation supply and firm-level relocation decisions in the study area and underscores the role of other firm and area-of-influence attributes in this process. The findings suggest a positive association between access to primary highway facilities and the level of economic activity. The results also confirm expectations that roads with higher functional form and capacity are likely to be more influential in the location and relocation decisions of businesses. The described model estimates could provide a basis for predicting the potential impact of local economic development policies in firm retention strategies.
Systems-Level Approach to Sustainable Urban Arterial Revitalization
Authors: Cherry Christopher R. , Deakin Elizabeth , Higgins Nathan , Huey S. Brian
Published: May 2018

Many cities in the United States are facing challenges associated with antiquated urban arterials, whose purpose has changed greatly since their development. Once considered the main streets of the city, with thriving businesses and attractive residential development, many have deteriorated over the decades for a number of reasons, including shifting demand for housing and retail development and the construction of parallel high-speed urban expressways. Because of the complexity of the problems associated with these arterials, a great challenge of transportation and land use planners is to develop a systems-level approach to revitalize and reinvent these arterials in a manner that encourages environmental, economic, and social sustainability. Presented is a methodology to revitalize multimodal urban arterials that includes land use planning, traffic and transit operations management, street redesign, and community participation to improve the conditions of such arterials. Analysis is carried out by using these principles on San Pablo Avenue, a major arterial in the San Francisco Bay Area in California. By using these analysis techniques, land use and transportation recommendations are made that will facilitate sustainable development along this corridor.
Finding Shortest Paths under Time–Bandwidth Constraints by using Elliptical Minimal Search Area
Authors: Han Lee D. , Wang Hui , Mackey William F.
Published: May 2018

Although many studies on shortest-path algorithms have been conducted, few of them have taken advantage of the added characteristics of highway networks and, thus, have failed to become more efficient in finding shortest paths, or lowest-cost paths, for transportation problems. A new concept is proposed for enhancing most existing shortest-path algorithms. Taking advantage of the geographical nature of most transportation networks, the new concept uses a minimal search area to reduce the amount of computations that must be performed by existing algorithms. To simplify the analysis, a hypothetical network in an L1 metric was used to approximate two-dimensional roadways. Empirical results from thousands of shortest paths between arbitrary origin–destination pairs suggested that an elliptical shape is most suitable for confining the search area when seeking a shortest path. Further analysis established the formulation of the ellipse, which becomes rounder when the origin is close to the destination and more elongated when the two points are far apart. The elliptical minimal search area is stable and has a high level of confidence in containing the true shortest path, even if the cost function for each link is dynamic or stochastic. A list of future tasks is presented to further the promising findings of this research. The algorithm, which is not in itself a shortest algorithm per se, can enhance other shortest-path algorithms for transportation roadway networks.
Influence of Land use on Tour Complexity
Authors: Maat Kees , Timmermans Harry
Published: May 2018

It is assumed that in new urban designs and compact cities, average travel distances tend to be shorter and more activities are linked in chains. As there is relatively little empirical evidence about the relationship between chain behavior and land use, especially from Europe, a study was done to obtain a better understanding of the influence of chains (referred to as tours) to test the hypothesis that compact urban forms reduce travel. The results indicate that higher densities lead not only to greater activity and greater tour demand but also to more complex tours. Although greater tour frequencies reduce mean tour distance, daily distance traveled increases. Moreover, complex tours have an encouraging effect on both tour distance and daily distance traveled. This confirms the hypothesis and previous evidence that more frequent tours and more stops per tour in high-density areas lead to more travel.
Impact of Mobile Phones on Travel
Authors: Srinivasan Karthik K. , Raghavender P. N.
Published: May 2018

Mobile phones are indispensable and ubiquitous tools that afford unprecedented levels of connectivity and accessibility to millions of users. A study investigated the influence of mobile phones on three travel-related dimensions: unplanned activity chaining, unplanned rideshares arranged by using mobile phones, and shopping by phone. These dimensions were investigated by using data from 400 workers in the city of Chennai, India. The results reveal that mobile phones significantly affect not only these travel dimensions but also activity participation. The data also provide evidence that social connectivity, activity characteristics, mobile phone use, and travel patterns are all strongly interlinked. Individual characteristics, such as flexible time and duration of working hours, and personal and household characteristics, such as age, gender, and vehicle availability, were found to be influential. The impact of mobile phones on the dimensions of unplanned stop making, ridesharing, and shopping trip substitution can have important practical implications for mode choice modeling, vehicle occupancy increase measures, and congestion alleviation measures.
Design Considerations for Detecting Bicycles with Inductive Loop Detectors
Authors: Kidarsa Richard , Pande Tarkesh , Vanjari Srinivas V. , Krogmeier James V. , Bullock Darcy M.
Published: May 2018

Inductive loop detectors are widely used for vehicle detection. Historically, these loop detectors have been installed by saw cutting 2-m-by-2-m octagons into the top 8 cm of a pavement. New construction practices often replace the octagon loop with a preformed circular shape and place this circular loop approximately 30 cm below the paved surface. Although such installation procedures provide acceptable detection for trucks and automobiles, their performance with bicycles is less clear. This paper develops a model of loop detector–bicycle interaction, verifies the model with field measurement, and provides plots documenting the location of bicycle detection zone hot spots adjacent to loop detectors. On the basis of the model, it is concluded that the performance of circular loops in detecting bicycles is almost identical to that of similarly wound octagon loops. However, when those loops are installed under the pavement, their ability to detect bicycles is significantly degraded. Because pave-over installation has several long-term life-cycle cost benefits, this paper suggests that when loops are installed in this manner, the loop closer to the stop bar be connected to its own individual loop detector, rather than wired in series, to improve its ability to detect bicycles.
Green Extension and Traffic Detection Schemes at Signalized Intersections
Authors: Tian Zong , Urbanik Thomas
Published: May 2018

This paper provides analyses of green extensions associated with two vehicle detection schemes for actuated signal control: the current single-channel detection and the emerging lane-by-lane detection. The current single-channel detection has all detectors across all lanes on a particular approach providing a single input to a signal phase. Lane-by-lane detection, however, monitors headways and gaps on a lane-by-lane basis. A simulation model was developed to analyze both detection schemes. With the simulation model, green extensions by the two detection schemes were compared over a wide range of traffic scenarios. On the basis of study results, it was found that the two detection schemes do not produce significantly different green extensions under normal traffic flow conditions. For the various factors examined, maximum allowable headway (also passage time) is found to be more sensitive compared with other factors such as arrival headway patterns and lane volume distribution. Although the difference between the two detection schemes in average green extension is generally minimal, large differences do exist among certain cycles, and the actual impact on signal operations could be more significant; this would need further evaluation with other standard traffic simulation models.
Limitations of Simultaneous Gap-Out Logic
Authors: Sharma Anuj , Bullock Darcy M. , Peeta Srinivas
Published: May 2018

The current practice of specifying simultaneous gap-out logic places constraints on signal controller logic. These constraints cannot be achieved under high traffic flow conditions, and degraded signal efficiency and dilemma zone protection often result. This study documents the phenomenon described above with set-back detectors at an instrumented intersection in Noblesville, Indiana, and characterizes the problem of dilemma zone protection as being traffic-volume dependent, a factor that should be carefully considered before the simultaneous gap-out logic is applied. Implementation of simultaneous gap-out logic led to max out ranging from 3.5% to 40% of cycles per hour during peak traffic flow periods and about 200 dilemma zone incursions per day. Results also indicate that simultaneous gap-out logic performs inefficiently and unsafely under high-volume conditions, whereas its performance is satisfactory under low-volume conditions. Analysis suggests an upper bound on potential savings of about 400 s of green time per day and a 25% reduction in dilemma zone incursions.
Design and Development of Integrated Arterial Signal Control Model
Authors: Vasudevan Meenakshy , Chang Gang-Len
Published: May 2018

This paper presents an arterial signal control system that provides arterial progression while optimizing signal timing plans at each intersection along the arterial. The proposed system is divided into two levels: progression control level and intersection control level. At the progression control level, arterial progression is provided by maximizing bandwidths using a modified version of the multiband model. In this study, unlike most bandwidth maximization models, queue clearance time and minimum green time are not prespecified, but are computed as a function of the existing queue at an intersection. At the intersection control level, signal timings are optimized for each intersection by minimizing a weighted combination of vehicle queue lengths, intersection control delays, and vehicle stop times, subject to bandwidths generated at the progression control level. The effectiveness of the system was evaluated through a case study conducted with CORSIM. Results showed that the proposed model was superior to actuated signal control implemented in the field and to the alternative that used the multiband model for signal progression. The proposed model resulted in significant reductions to control delays, stop times, and queues in addition to increases in throughput and speeds. Compared with the multiband model, the proposed model reduced arterial queues by 11%, control delays by 12%, and stop times by 14%. Compared with actuated signal control, benefits were greater, with reductions of 24% in vehicle queues, 17% in control delays, and 15% in stop times along the arterial.
System Optimal Signal Optimization Formulation
Authors: Beard Christopher , Ziliaskopoulos Athanasios
Published: May 2018

A mixed-integer linear programming formulation is proposed to solve the combined system optimal dynamic traffic assignment and signal optimization problem. Traffic conditions are modeled with the cell transmission model, a convergent numerical approximation to the hydrodynamic model of traffic flow. The formulation is suited to respond to oversaturated traffic conditions. It also can be adapted to account for turning movements, protected and permissive phases (gap acceptance), and multiple signal controller types: dynamic (traffic adaptive) and pretimed. Trials with a test network validated the formulation and achieved promising results. Specifically, dynamic signal control proved to be substantially more effective than pretimed control for incident conditions. In addition, potential benefits of rerouting vehicles in both directions of a roadway were revealed even when only one direction is closed.
Determination of Optimal Detector Location for Transit Signal Priority with Queue Jumper Lanes
Authors: Zhou Guangwei , Gan Albert , Zhu Xiaoxia
Published: May 2018

Transit signal priority (TSP) is an operational strategy that facilitates movement of transit vehicles through signalized intersections. As an important component of a TSP system, the transit vehicle detection system plays a key role in determining when to trigger TSP and which TSP strategy to use. This paper presents an analytical method to determine optimal detector locations for intersections implemented with TSP and queue jumper lanes. A queue jumper lane is a preferential treatment for buses that designates a short stretch of a special lane, such as a right-turn bay, to allow buses to bypass a traffic queue and then to proceed ahead of the queue by means of an early green signal for that lane. In this study, a comprehensive TSP strategy was used that considers early green, green extension, special phase insertion, coordination recovery, green reimbursement, and maximum number of continuous TSP requests. An analytical method for determining optimal detector locations under this TSP strategy for different bus arrival conditions was proposed. The effectiveness of the proposed method was verified with the VISSIM microsimulation model, and results show that the method is able to identify optimal bus detector locations for TSP with queue jumper lanes.
Development and Field Testing of Platoon Identification and Accommodation System
Authors: Chaudhary Nadeem A. , Abbas Montasir M. , Charara Hassan A.
Published: May 2018

This paper describes the development and initial field testing of an intelligent traffic control system for identifying and progressing platoons at isolated traffic signals on signalized arterials. This system uses advance detection to obtain real-time information about the presence and speeds of individual vehicles. Its algorithm identifies whether a platoon—of a user-specified minimum size and density—is approaching the signal and estimates platoon arrival time at the stop bar. When warranted, the system issues a low-priority preemption signal to progress the detected platoon. Duration of the initial preemption signal is based on estimated arrival and departure times for the smallest acceptable platoon and the estimated time needed to clear any queues present at the signal. Then, the system switches to an extension mode and provides progression to any additional vehicles determined to be in the platoon. It accomplishes that by increasing preemption time until no more vehicles are determined to be in the platoon or until the max timer expires. The system also ensures that the last progressed vehicle is not trapped in its dilemma zone. The platoon identification and accommodation system can be implemented by retrofitting existing National Electrical Manufacturers Association cabinets.
Dynamics of Variable Speed Limit System Surrounding Bottleneck on German Autobahn
Authors: Bertini Robert L. , Boice Steven , Bogenberger Klaus
Published: May 2018

This paper presents findings of an ongoing empirical study focusing on identification and examination of several recurring freeway bottlenecks. It integrates the fusion of several traffic management and driver information data sources along an 18-km (11.2-mi) section of Autobahn 9 near Munich, Germany. These combined data sources further understanding of traffic dynamics and driver behavior before, during, and after bottleneck activation. The primary focus of this paper has been the investigation of variable speed limit and traveler information systems provided by means of overhead dynamic message signs so as to improve understanding of how these systems affect driver behavior and bottleneck formation and location. Toward that end, speed limit and information messages have been compared with actual traffic dynamics on the segment of Autobahn 9, and the analysis has found a strong correlation. It has been found that when drivers were warned of approaching congested conditions, the speed limit was reduced before bottleneck activation as a means of managing dense traffic. The system reduced the speed limit to control dense but still flowing traffic, and traffic continued to flow during congested periods at speeds between 30 and 40 km/h (19 and 25 mph). A comparison of sampled measurements of flow and speed with fundamental diagrams of speed–flow and flow–density indicated that speed limits were reduced. These findings will be connected to a before-and-after comparison of the system to be done to determine benefits and effects of such a system.
Purchasing Travel Time Data
Authors: Smith Brian L.
Published: May 2018

Given recent advances in technology that support probe-based traffic monitoring, many transportation agencies are considering purchasing travel time data from private providers to supplement or replace data currently collected using agency-owned point sensors. Although this new approach potentially offers significant benefits, it also brings substantial risk. To mitigate the risk, it is essential that agencies develop clear, thorough requirements to use in travel time data purchasing agreements. The purpose of this research was to develop proposed travel time data service requirements. First, the research team conducted a critical analysis of expected data users and their applications. On the basis of that analysis, proposed requirements were developed in the following categories: ( a) travel time measure requirements defining what data should be provided in the agreement, ( b) spatial coverage requirements defining the directional link structure that should be used for travel time measurements, ( c) temporal requirements defining the measurement time intervals, ( d) data quality requirements defining minimum acceptable data quality to be provided, ( e) data quality validation requirements defining the methodology to use in assessing data quality, and ( f) data use requirements defining acceptable uses of the data by the purchasing agency.
Linking Planning and Operations to Improve Regional Mobility and Safety in Hampton Roads, Virginia
Authors: Ravanbakht Camelia , Akan Guzin , Hanshaw Stephany , Allsbrook Lynn
Published: May 2018

The Transportation Equity Act for the 21st Century identifies seven planning factors that must be considered in the transportation planning process. One of these factors requires that states and metropolitan planning organizations (MPOs) promote efficient system management and operation and establish a formal role for management and operations (M&O) activities in the transportation planning process. In support of this requirement the Hampton Roads Planning District Commission, the designated MPO for southeastern Virginia, has been aggressively involved in addressing transportation M&O under the structure and auspices of regional transportation planning. Recognizing the need for intergovernmental cooperation and technical innovations to meet planning for M&O activities and challenges, the Hampton Roads MPO formed the Intelligent Transportation Systems (ITS) Technical Committee in the early 1990s. In many ways the Hampton Roads region has long been on the leading edge of ITS planning efforts. The region pioneered development of an early deployment plan in 1995 and was also an early adopter of an ITS regional architecture. There is a strong partnership and collaboration among the region's ITS stakeholders. This paper focuses on planning efforts used in integrating ITS and M&O activities into the mainstream of the regional transportation planning process in Hampton Roads. The paper describes key elements and the process undertaken by key players to ensure integration for achieving a safe and efficient transportation system in the Hampton Roads region.
Mitigating Alkali–Silica Reaction in Concrete Containing Recycled Concrete Aggregate
Authors: Li Xinghe , Gress David L.
Published: May 2018

This work involves research on the use of fly ash to mitigate alkali–silica reaction (ASR) in concrete made with recycled concrete aggregate (RCA) that comes from concrete with a known ASR history. Modified ASTM C 1260 and C 1567 with different aggregate grading showed that a 25% cement substitution with a Class F fly ash controlled the expansion under 0.10% at 28 days. RCA from I-95 near Gardiner, Maine, was selected for this study. The RCA, coarse aggregate recovered from the RCA, and currently produced aggregate from the same source as the RCA were evaluated in the laboratory. The conventional ASTM C 1260/1567 14-day expansion results correlated well with ASTM C 1293 1-year criteria. The ASR-modified ASTM C 1260/1567 28-day expansion results also correlated well with ASTM C 1293 2-year failure criteria. Pore solution and thermal gravimetric analysis revealed both calcium hydroxide and alkalis are reduced by fly ash substitution. Calcium depletion alone is a sufficient condition for ASR arrest, but the substitution level, depending on the portland cement, can be as high as 60% and unusable in field concrete. Approximately 25% fly ash substitution was required to lower the pH to a range of 13.28 to 13.32, a presumed ASR threshold range. The effect of alkali reducing appears to be more pivotal than calcium consumption. Although alkalis were found to be present in the RCA, it was not shown that it was available to the pore solution. This suggests that alkali concentration in the new paste and the old RCA matrix are approximately equal and therefore in equilibrium with each other.
Capping Systems for High-Strength Concrete
Authors: Torres Sadí , Eggers John
Published: May 2018

This study focused on the effects of capping systems on the compressive strength of high-strength concrete (HSC). The three systems investigated were ground ends, bonded caps, and unbonded pads. Five compressive strength groups were examined with strength levels ranging from 6,000 psi to 14,000 psi. The capping compounds investigated were commercially available and advertised for testing HSC. The unbonded pads were neoprene pads with a Shore A Durometer hardness of 70. A grinding machine was used to obtain the required planeness and perpendicularity on the ground end cylinders. No significant difference was found between the capping systems at the 6,000-psi, 10,000-psi, and 14,000-psi levels. Significant differences were detected at the 8,000-psi and 12,000-psi levels. In the 8,000-psi group, ground ends produced significantly lower compressive strengths than three of the capping compounds. For the 12,000-psi group, ground ends produced significantly lower strengths than one of the capping compounds and the unbonded pads. In all strength levels but the 6,000-psi level, the ground ends method produced lower average compressive strengths than the other methods studied. These results imply the viability of alternative methods of end treatments such as unbonded pads and capping compounds for use with HSC.
Long-Term Effects of Magnesium Chloride and Other Concentrated Salt Solutions on Pavement and Structural Portland Cement Concrete
Authors: Sutter Larry , Van Dam Thomas , Peterson Karl R. , Johnston Daniel P.
Published: May 2018

Many state highway agencies use various chemicals to deice or anti-ice pavement and bridge surfaces. Most often these are aqueous solutions of various chlorides (e.g., magnesium chloride, sodium chloride, and calcium chloride) or other chemicals such as calcium magnesium acetate, urea, or others. Possible detrimental effects to concrete caused by these chemicals have not been fully examined and documented. Mortar specimens of three different water-to-cement ratios (0.4, 0.5, and 0.6) were immersed in concentrated solutions of various chemical deicers and held above freezing at a constant temperature of 40°F up to 84 days. Considerable expansion and cracking were noted in specimens immersed in the MgCl2 and CaCl2 solutions. Petrographic analysis and quantitative microanalysis were used to positively identify the presence of Mg(OH)2 (brucite) formation in the outer layers of the specimens. Furthermore, the results presented clear evidence of calcium oxychloride formation in the specimens analyzed. Further research is being conducted, including the same immersion test at 40°F on portland cement concrete specimens, to identify whether this distress mechanism is of concern for structures such as roads and bridges when subjected to deicing chemicals containing CaCl2 or MgCl2.
Investigation into Potential of Alkali–Acetate–Based Deicers to Cause Alkali–Silica Reaction in Concrete
Authors: Rangaraju Prasada Rao , Sompura Ketan R. , Olek Jan
Published: May 2018

Recent investigations by the FAA into the condition of airfield pavements have indicated increased occurrence of premature deterioration in concrete pavements, particularly caused by alkali–silica reaction (ASR). On the basis of the evidence, it was suspected that certain deicing chemicals used on the pavements may have been responsible for the distress. This paper presents the results from a study conducted to investigate the effect of potassium acetate–and sodium acetate–based deicers on causing ASR in test specimens. A modified ASTM C 1260 test procedure was used in this study, in which mortar bars prepared with reactive aggregates were soaked in deicer solutions, instead of 1 N sodium hydroxide solution as in the standard ASTM C 1260 test. Tests were conducted on four reactive aggregate sources and one nonreactive aggregate, using a low-alkali and a high-alkali cement. In addition, standard ASTM C 1260 tests were conducted on all aggregates considered in this study. The effect of concentration and temperature of soak solutions on the observed expansions of mortar bars was also investigated. Length-change measurements, dynamic modulus of elasticity, scanning electron microscopy, and energy dispersive X-ray analyses were conducted on test specimens. The pH values of the soak solution were monitored to observe any interactions between the soak solution and the mortar bars. On the basis of this research, it was found that the two common airfield deicing chemicals—potassium acetate–and sodium acetate–based deicer solutions—have a significant potential to cause ASR in test specimens containing reactive aggregates.
Efforts to Improve Durability of Concrete in Virginia
Authors: Ozyildirim Celik
Published: May 2018

This paper addresses some of the notable improvements in the durability of concrete for bridge structures, mainly decks, and of pavements by the Virginia Department of Transportation since 1938. These improvements are intended to extend service life with minimal maintenance. Improvements have been made in the design, material ingredients, proportioning, and construction practices for bridge structures and concrete pavements.
Impact of Highway Safety Flares on Driver Behavior
Authors: de la Riva Miguel , Garvey Philip M. , Pietrucha Martin T.
Published: May 2018

In the United States, nearly 350,000 parked or disabled motor vehicle crashes occur annually; these crashes cause the deaths of an average of 507 occupants and nonmotorists and injury to more than 30,000 people. Among safety measures aimed at reducing the frequency and severity of this type of crash, the deployment of flares is widely recommended and publicly accepted. The research presented supplements the literature on highway safety flare use by addressing the relative nighttime effectiveness of the number of flares, placement and spacing of flares, and use of flares with and without the additional activation of a police vehicle's light bar. The behavior of almost 4,000 passing vehicles was observed unobtrusively through the use of roadway sensors that counted the number and type of vehicles passing the study area and measured passing vehicle speed, lane distribution, and lateral separation from the roadway edge. Flare use had a significant and positive impact on all the dependent variables.
Effects of Adaptive Cruise Control and Alert Modality on Driver Performance
Authors: Lee John D. , McGehee Daniel V. , Brown Timothy L. , Marshall Dawn
Published: May 2018

Adaptive cruise control (ACC) is a rapidly emerging in-vehicle technology that can enhance or degrade driving safety. A critical factor governing the safety benefit of ACC concerns the driver's ability to assume control of the vehicle in situations that exceed ACC capabilities. The effectiveness of various warning modalities for reengaging distracted drivers during severe braking situations that exceed ACC capability was examined. Warnings that paired a visual icon with sound, seat vibration, or brake pulsation or that combined all three cues were compared. A total of 60 participants drove for 35 min in the National Advanced Driving Simulator. Drivers experienced two severe, four moderate, and eight mild braking situations. ACC could accommodate all but the two severe situations without driver intervention. It also provided a substantial benefit during mild events of lead vehicle braking, enabling drivers to maintain a longer, more consistent minimum time to collision. Unlike performance in previous studies, ACC did not decrease safety during severe braking situations. The combination of a visual icon with sound, seat vibration, or brake pulsation led to slower brake reaction time in severe braking situations, but the grouping of all four warning strategies led to a similar minimum time to collision and maximum braking. In contrast to several previous studies, these results suggest that drivers can effectively assume control when warned that ACC braking authority has been exceeded. Additional research is needed to identify the boundary conditions that specify when drivers can successfully intervene and retake control and whether a multimodal combination of cues can be crafted to speed rather than slow driver response.
Eyeglance Behavior of Novice Teen and Experienced Adult Drivers
Authors: Lee Suzanne E. , Olsen Erik C. B. , Simons-Morton Bruce
Published: May 2018

Eyeglance behavior and scanning patterns may be learned as a driver gains experience and lead to greater situation awareness on the part of the driver. This may help to explain differences observed in the safety records of novice teen and experienced adult drivers. For example, new drivers may focus almost exclusively on the road ahead and spend little time scanning the vehicle's mirrors. However, a novice driver performing a secondary task may spend more time with his or her eyes on the task than on the road, because of unfamiliarity with the vehicle or inexperience with consequences of long glances away from the forward view. For this study, 18 novice teen (under 17.5 years old and within 4 weeks of licensure) and 18 experienced adult drivers performed a set of in-vehicle tasks on a test track. A baseline driving segment was also included. Measures consisted of percentage of eyes-off-road (EOR) time, number of glances, and mean single-glance time. Results showed that teens glanced at the rearview mirror significantly fewer times than did adults, both during baseline driving and while performing in-vehicle tasks. Teens also had a significantly higher percentage of EOR time than adults had while performing a challenging reading task. The novice teen drivers spent more of their overall EOR time looking at the task display (e.g., cell phone), whereas adults used some EOR time to check mirrors or windows. Overall findings indicate that novice teens may lack the situation awareness of experienced adults.
How Multitasking Interacts with Visual Impairment and Age on Measures of Driving Performance
Authors: Wood Joanne M. , Chaparro Alex , Carberry Trent , Hickson Louise
Published: May 2018

This study investigates the impact of visual and auditory secondary tasks on the driving performance of participants (14 younger and 14 older) with simulated visual impairment. Participants drove around a closed road circuit under single- and dual-task conditions. Driving performance measures included road sign recognition, detection and avoidance of low-contrast hazards, gap judgment, and time to complete the course. Driving with two levels of visual impairment was compared against a baseline condition: goggles designed to replicate the effects of cataracts or blur (uncorrected refractive error visual impairment were used to simulate), and goggles were used to reduce binocular visual acuity to a mean level of 20/40. Secondary tasks required participants to add orally pairs of numbers presented through a computer speaker (auditorily) or via a dashboard-mounted monitor (visually). Results indicate that visual impairment significantly reduces driving performance ( P < 0.05) and the differences are greatest under the cataract condition. Multitasking (e.g., talking on a cell phone or using in-vehicle navigational devices) further exacerbated these effects, and the visual dual task had a greater detrimental effect on driving performance than did the auditory dual task ( P < 0.05), particularly for the older drivers. Overall, results indicate that multitasking impairs driving performance and the effects are exacerbated for older drivers and younger drivers with visual impairment. This finding has important implications as driving and in-vehicle environments become increasingly complex and older people comprise the fastest-growing segment of the driving population.