bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring Engagement in Household Activities and Decisions on Residential Tenure and Household Type
Authors: Chen Roger B. , Gehrke Steven R. , Liu Jenny H. , Jang Yunemi , Clifton Kelly J.
Published: November 2013

Residential locations play an important role in the spatial distribution of household activities and travel decisions and, subsequently, in long-term forecasting models. This study examined the relationship between housing location choices, time allocation to out-of-home activities, and other socioeconomic attributes related to household life-cycle stages. A choice model of housing tenure and type was formulated and estimated to provide a methodological framework for examining the impacts of engagement in household activities and life-cycle stage. Engagement in household activities was represented by factor scores from a factor analysis on the proportion of time households spent on 14 activity types. The scores of the identified factors, in addition to other socioeconomic and travel characteristics of the household, were estimated in a nested-logit choice model of housing tenure and type. Furthermore, households were segmented into different life-cycle stages on the basis of household size and age of members. Results from this study revealed that the life-cycle stage of a household had a significant statistical impact on the tenure choice to rent relative to the choice to own a home. In relation to time allocation for household activities, the time allocated to eating, recreation, and social activities was found to have the strongest statistical significance with respect to the choice of tenure and housing type. Overall, estimation results revealed a relationship between the choice of housing tenure and type, attributes of the household, and the allocation of activity time among its members.
Temporal Stability of Generation Choice Models
Authors: Huntsinger Leta F. , Rouphail Nagui M.
Published: November 2013

This paper evaluates the temporal stability of generation choice models by considering two cases. The first case evaluates temporal stability with widely used explanatory variables, and the second examines whether temporal stability improves with the inclusion of life cycle, area type, and accessibility. The results of this research show that generation choice models, with their ability to estimate person trips and accommodate more variables that define the traveler and the trip, are temporally stable for home-based work trips by workers and home-based other trips by nonworking adults. Home-based other trips by workers show mixed results with respect to temporal stability, while home-based other trips by children do not pass the test of temporal stability with any of the measures considered. This research shows that, while life cycle, area type, and accessibility variables help explain travel behavior, they provide little, if any, additional benefit with respect to temporal stability.
Assessment of Sustainability for Transportation Vehicles
Authors: Mitropoulos Lambros K. , Prevedouros Panos D.
Published: November 2013

Traditional urban planning ignores vehicle technology, including the large differences between conventional-, hybrid-, and alternative-fuel vehicles and buses. This study develops an assessment framework that has its foundations in the overarching principle of sustainability. The framework is composed of five sustainability dimensions: environment, technology, energy, economy, and users. From these dimensions, a set of indicators was developed for assessing the sustainability performance of five urban transportation vehicles. The indicators are based on vehicle life-cycle impacts and measure individual vehicle features that contribute to maximizing sustainability. The assessment reveals that the hybrid diesel–electric bus and the hybrid electric vehicle have the highest scores. Performance indices by vehicle type provide the basis for a sustainability tool. The tool was applied to a corridor in Honolulu, Hawaii, to assess the sustainability performance of three scenarios for mode share. Results show that modern propulsion systems can improve the overall sustainability performance relative to the technologies of the internal combustion engine. The sustainability performance of some new technologies currently suffers from limitations in engine and battery performance, comfort and convenience, and availability of charging stations.
Mixed-Use Development Trip Generation Model
Authors: Gulden Jeff , Goates J. P. , Ewing Reid
Published: November 2013

The mixed-use development (MXD) trip generation model provides a mechanism for estimating vehicle, walking, and transit trips for an MXD. The model applies trip modifications to standard single-use trip generation estimates developed by ITE. MXDs with diverse internal activities have been shown to capture internal trips at a rate higher than conventional suburban developments; therefore, the MXD trip generation model accounts for the internal capture of MXD sites by reducing the external trips produced and estimating the number of walking and transit trips that would typically be conducted by automobile. In addition, MXDs in central areas have been shown to generate shorter vehicle trips, and this factor has been taken into account in the model, as internal and external vehicle miles traveled (VMT) are estimated on the basis of published travel characteristics of MXDs. The MXD trip generation model provides a straightforward method of testing transportation-related metrics of MXDs. The model uses ratios from a leading research-based MXD model to reduce ITE vehicle trip estimates and presents a summary of results that show the effects on VMT, internal capture, and mode split as a result of enhanced activity density and diversity of land uses within the MXD. The MXD trip reductions are based on a methodology that analyzed data sets for 239 MXDs in six large and diverse metropolitan regions. Benefits of locally calibrated characteristics on vehicle ownership are also included in the mode split of the trip estimates of the MXD trip generation model.
Evolving ITE Trip Generation Handbook
Authors: Clifton Kelly J. , Currans Kristina M. , Muhs Christopher D.
Published: November 2013

This paper outlines a new perspective on data collection to inform site-level trip generation studies with amendments to ITE's Trip Generation Handbook in mind. The data collection proposed here is informed by the authors’ experiences in a study that aimed to adjust trip generation rates for an urban context. In this study, a consistent, reliable method for adjusting ITE's trip generation rates to account for increased non-automobile travel in different urban contexts was developed. On the basis of these experiences, the design presented here proposes more emphasis on collecting information on person counts and on how those person trips are distributed across various modes, including walking, cycling, and transit. This paper advocates a move from the vehicle-based counts used historically in these studies to a focus on how new development affects all users of transportation systems.
Destination Choice Model for Commercial Vehicle Movements in Metropolitan Area
Authors: Mei Bing
Published: November 2013

This paper describes the development of a destination choice model for the movements of commercial vehicles in a metropolitan area. The proposed model has two major differences from other regional commercial vehicle models in the United States: (a) the model is stratified by commercial vehicle type and trip purpose jointly, instead of by vehicle type only; and (b) the model employs the technique of discrete choice modeling instead of using a traditional gravity model. With this technique, nonimpedance variables could be tested for inclusion in the utility function of the model. The study found that, besides travel time being a strong predictor, interarea-type dummy variables were statistically significant in truck-related submodels that push truck trips to less developed areas. Intercounty dummy variables were attempted as a proxy for intercounty economic interaction and found statistically significant in several submodels. Both the interarea-type and intercounty dummy variables add explanatory power to the model. The model estimation results indicate that the model fits the data well, with likelihood ratio index (ρ2) values ranging from .24 to .32. This research effort demonstrates that a destination choice model stratified by both vehicle types and trip purposes can be successfully developed and employed for modeling commercial vehicle trip distribution.
Establishing Values of Time for Freight Trucks for Better Understanding of Impact of Toll Policies
Authors: Mei Qinfen , Hussein Mazen I. , Horowitz Alan J.
Published: November 2013

Many freight models have considered only travel time as the path building criterion, but truck drivers are sensitive to both time and cost when choosing routes. In addition, a key variable in understanding a driver's choice when in the presence of tolls is the value of a driver's time. Research has suggested that values of time (VOT) vary considerably by the parameters of the haul, principally the type of truck and the commodity carried. Behavioral methods of ascertaining passenger VOT are limited by the variety of VOT that can be conveniently obtained, while the number of commodities and truck types to carry them are large. Fundamentally, truck drivers attempt to minimize costs, although they may do so imperfectly. This paper uses a policy-sensitive truck cost model to obtain VOT and tests those on a full-scale simulation. A highly-detailed cost model of trucking was previously developed by the research team for the purposes of policy analysis. This cost model originally followed industry practice by basing most cost components on the length of haul, which would imply that truckers would mostly minimize distance when choosing routes. However, many cost components are more logically related to the time duration of the haul. This leads to two possible hypotheses, time- and distance-based costs and distance-based costs, each resulting in different VOT. VOT were tested by simulating truck traffic in a 10-state region that included numerous toll facilities. Comparisons of the simulation results to actual traffic data from automatic traffic recorder stations from the State of Ohio and from counts provided by the Ohio Turnpike Authority suggest that VOT more closely follow the time- and distance-based cost hypothesis.
Modeling Long-Distance Travel in Great Britain
Authors: Rohr Charlene , Fox James , Daly Andrew , Patruni Bhanu , Patil Sunil , Tsang Flavia
Published: November 2013

Trips longer than 50 mi account for less than one-fortieth of all trips but nearly one-third of all distance traveled within Great Britain. Because of the small proportion of all travel that they form, long-distance trips may not be adequately represented in national databases and models. However, because they account for a substantial proportion of total distance traveled, particularly on motorways and rail, these trips are important for transport policy and have a substantial impact on congestion. Moreover, study of existing data indicates that travelers’ behavior in longdistance journeys differs substantially from that in routine journeys. Not only is the set of available modes different, but the profile of travelers is also substantially different, with income playing an important role in both travel frequency and mode choice. In addition, model responsiveness and values of time vary significantly with journey length. For these reasons, treatment of the specific properties of long-distance travel is essential for appraising the impact of transport policy aimed at this market, such as high-speed rail, highway construction and management policies, and policies directed toward domestic air travel. This paper describes the development of a model to address these policy issues. The specific aim of the modeling work is to provide empirical evidence on the relative importance of mode, destination, and frequency responses for long-distance travel models. The models that have been developed form the basis for a forecasting model that can be used for the appraisal of a wide range of transport policy aimed at long-distance journeys.
Design and Evaluation of an Intelligent Dilemma-Zone Protection System for a High-Speed Rural Intersection
Authors: Chang Gang-Len , Franz Mark L. , Liu Yue , Lu Yang (Carl) , Tao Ruihua
Published: November 2013

This paper presents the design and evaluation of a dilemma-zone protection system that uses dynamic detection technology to track individual vehicles as they approach an intersection of interest. A high-speed rural intersection in Maryland experiencing a high crash frequency was selected for system installation and evaluation. Data were collected from three sensors designed specifically for tracking individual vehicles and deployed along the target approach. The sensors were used in real time to control the signal logic and provided green or all-red extensions when the predefined parameters of detected vehicles were met. A field test was conducted to evaluate the performance of the system design and the effectiveness of the associated parameters. The data analysis included the identification of falsely called red extensions (related to efficiency) and missed red extensions (related to safety) to assess the overall performance of the newly installed system. The field observation results indicate that the newly designed dynamic dilemma-zone protection system using an all-red extension offers distinct advantages over traditional systems by providing additional protection to highspeed vehicles even when they are in the “cannot go” zone and make an incorrect decision to go.
Experiences with Adaptive Signal Control in Germany
Authors: Brilon W. , Wietholt T.
Published: November 2013

Germany has a long tradition of traffic-actuated and -coordinated signal control. In recent years a specific approach to traffic actuation called a model-based system, or adaptive control, has found its way into practice. In the city of Muenster, Germany, the coordinated signal control system on the 6-km-long arterial Albersloher Weg, with 24 signalized intersections, has been completely renewed in a three-step process involving the old system, a rule-based traffic-actuation system, and an adaptive system. An empirical evaluation of this process by a university research team showed that conventional actuated signal control improved traffic performance in the first step. Additional significant improvement (as much as 30%) in traffic flow performance could be achieved by implementing Motion, an adaptive signal control system. However, further developments are required to meet the expectations of city engineers and road users. In particular, switching between optimized signal plans, which is an essential feature of the Motion system, must be improved.
Estimating Queue Length under Connected Vehicle Technology
Authors: Li Jing-Quan , Zhou Kun , Shladover Steven E. , Skabardonis Alexander
Published: November 2013

With the emergence of connected vehicle technology, the use of probe trajectory data to estimate queue length has recently received considerable attention. Unlike data collected by loop detectors, probe trajectory data can provide a lower bound on the queue length even if the market penetration rate is low. An event-based method is developed: it uses both probe trajectory and signal timing data to estimate queue length, and the estimation accuracy under different market penetration rates is examined. A data fusion method is developed: it combines probe trajectory data and loop detector data, and the situation in which the data fusion method is expected to work well is investigated. Case studies are conducted with microscopic simulation data, and some observations are made.
Transit Priority Strategies for Multiple Routes under Headway-Based Operations
Authors: Lin Yongjie , Yang Xianfeng , Chang Gang-Len , Zou Nan
Published: November 2013

This paper presents a transit signal priority (TSP) model designed to consider the benefits both to bus riders and to intersection passenger car users. The proposed strategy, which is mainly for headway-based bus operations, offers the responsible agency a reliable way to determine the optimal green extension or red truncation duration in response to multiple bus priority requests from different routes. The control objective is to minimize bus passenger waiting time at the downstream bus stop while ensuring that the delays for all passengers are not increased. In tests that used field data from Jinan, China, the proposed strategy showed promise in reducing bus passenger waiting time and total intersection delay. Further exploration with simulation experiments for sensitivity analysis found that TSP is most effective if the ratio between bus and passenger volumes exceeds a threshold of 2%.
Multiregime Adaptive Signal Control for Congested Urban Roadway Networks
Authors: Xin Wuping , Chang Jinil , Muthuswamy Satya , Talas Mohamad , Prassas Elena
Published: November 2013

A hierarchical adaptive signal control was developed and implemented in New York City to manage congestion in a complex urban roadway environment. Control strategies, including strategically regulating traffic demand and balancing the queue–storage ratio at critical intersections, work in concert to systematically alleviate congestion and improve mobility. The high usage of electronic toll collection tags in this area allows large amounts of per trip travel time data to be collected (nearly 1 million per trip travel time records daily) and used in real time for effective control. Congestion levels are mapped to different control regimes. Various demand-regulating strategies are applied at the peripheral roadways of the target control zone. These strategies proactively employ signal offsets and splits to exert a tapering and rebalancing effect on the traffic. Demand regulation results in a better use of available network storage spaces while preserving the capacity of the target control zone. Inside the target control area, a dynamic queue-balancing strategy is implemented at selected critical intersections to prevent propagation of spillovers with stabilized or diminished queues. The initial implementation covered 110 intersections in the highly congested central business district of midtown Manhattan New York City. Results to date are summarized.
Effects of Metered Entry Volume on an Oversaturated Network with Dynamic Signal Timing
Authors: Medina Juan C. , Hajbabaie Ali , Benekohal Rahim (Ray) F.
Published: November 2013

This paper analyzes the effects of different traffic metering levels at the entry points of a simulated signalized network to maintain efficient vehicle processing. Metering signals were placed along the network perimeter in advance of the bordering intersections to reduce the vehicle arrival rate and prevent oversaturation. In the simulation environment, traffic signals were externally controlled by independent agents using a learning algorithm based on approximate dynamic programming. Agents operated the signals in a cycle-free mode, reacting in real time to current demands and occupancy estimated from detectors placed at the entry and exit points of all links. The metering strategies were analyzed for delay, throughput, network congestion, and queue management. Results indicate that metering have a significant effect on network performance. Metering to levels just below the maximum throughput capacity of an intersection resulted in increased network throughput (up to 5%); reduced delay (up to 10.9%), including vehicles inside and those metered outside of the network; and queue lengths inside the network that allowed efficient use of green time. However, metering to points well below or above the capacity of an intersection did not always provide network improvements. This finding suggests that an optimal congestion level exists inside the network that can be achieved by a metering strategy. An analysis of the metering effects is presented in a case study, and field implementations and scenarios in which metering can be applied are discussed.
Arterial Queue Spillback Detection and Signal Control Based on Connected Vehicle Technology
Authors: Christofa Eleni , Argote Juan , Skabardonis Alexander
Published: November 2013

Queue spillbacks are a major problem in urban signalized arterials because such spillbacks can lead to gridlock and excessive delays. Several methods based on fixed-location detector data have been proposed to identify the occurrence of queue spillbacks and implement signal control strategies to mitigate their impacts. This paper presents two queue spillback detection methods based on connected vehicle (CV) or probe data. The first method requires only the use of CV data and is based on the notion that nonequipped vehicles in queue that arrive after the last CV-equipped vehicle can be modeled by using a geometric distribution. The second spillback detection method combines CV data with information about the signal settings at the upstream intersection and is based on a kinematic wave theory of traffic. The authors also developed a signal control strategy to mitigate queue spillbacks once they were detected. The proposed queue spillback detection methods and alternative signal control strategy were tested through simulation on a four-signal segment of San Pablo Avenue in Berkeley, California. The results show the penetration rate thresholds of CV-equipped vehicles required for accurate queue detection. The proposed signal control strategy improved traffic operations for the upstream cross streets without compromising traffic operations on either direction of the arterial traffic and substantially reduced the variation of the queue length on the critical arterial link.
Dynamic Programming Approach for Arterial Signal Optimization
Authors: Gartner Nathan H. , Deshpande Rahul M.
Published: November 2013

Link performance functions (LPFs) are essential components of macroscopic models for signal optimization, traffic assignment, or combined control-assignment models. Numerous studies have developed a variety of performance functions for signal optimization. Most of these studies attempted to use simplified LPFs that did not capture the important relationships and dependencies among the variables. Dependent LPFs are introduced; in these LPFs the performance on any link depends on the flow pattern not only on that link alone but also on the feeder links. Such functions represent with greater fidelity the performance characteristics of the link and can lead to better control and assignment. An optimization model explicitly considers flow interactions among successive links and applies it in a dynamic programming procedure to determine optimal signal settings. The procedure, which is an offshoot of the combination method for offset optimization, is illustrated for an arterial street and demonstrates its efficacy in comparison with existing optimization models.
Self-Organizing Control Logic for Oversaturated Arterials
Authors: Cesme Burak , Furth Peter G.
Published: November 2013

Decentralized, actuated traffic signal control has many advantages, but it lacks mechanisms for coordinating with other signals along an arterial. When an intersection along an arterial is near or at oversaturation, coordination can play an important role in preserving and utilizing capacity by preventing spillback and starvation. Rules that can be added to a base of decentralized, clock-free actuated control are proposed for managing queues during periods of oversaturation. These rules are part of a larger framework for developing logic that will make arterial traffic signals self-organizing rather than organized around a common signal cycle. Features of the proposed logic include green truncation in case of intersection spillback, early green and double realization for left-turn phases prone to pocket spillback resulting from a limited turn-bay length, and dynamic coordination for groups of signals spaced too close together to hold a normal cycle's queue. With dynamic coordination, green waves are scheduled for each cycle following the critical intersection's critical arterial through phase, with noncritical intersections adjusting offsets based on queue counts and a logic. The proposed dynamic coordination logic allows temporary spillback at upstream intersections to prevent starvation at the critical intersection and temporary starvation at downstream intersections to prevent spillback at the critical intersection. Simulation tests using a benchmark network showed 45% less delay than standard coordinated control and 4% less than an optimizing control method designed for oversaturated arterials. Simulation tests on two realistic networks also showed delay reductions of 8% and 35% compared with coordinated control.
Evaluation of Microwave Radar Vehicle Detectors at a Signalized Intersection under Adverse Weather Conditions
Authors: Medina Juan C. , Ramezani Hani , Benekohal Rahim (Ray) F.
Published: November 2013

Two microwave radar systems for vehicle detection, manufactured by Wavetronix and MS SEDCO, were evaluated at stop bar and advance zones of a signalized intersection under three adverse conditions: (a) high wind speeds, (b) rain, and (c) fully or partially snow-covered roadway. Data under normal (favorable) weather conditions were also analyzed and used for comparison. Results show that the performance of the two systems deteriorated during adverse weather, and the type of detection errors and their frequency were system dependent. In general, wind increased false calls at the advance detection zone by more than 50%, depending on the location and sensor type; snow-covered roadway had more widespread effects and increased false calls at stop bar and advance zones, depending on the system, and also increased missed calls at stop bar zones; and rain affected the two systems by increasing false calls and stuck-on calls at the stop bar and false calls at the advance zones. Data also showed that frequencies of false and missed calls were likely to increase as precipitation intensity and wind speeds increased. Results from this evaluation show significant effects of adverse weather on microwave radar detection systems, providing information to researchers and practitioners regarding the potential performance of similar setups under such conditions. Details on the detection errors offer insight on situations that should be monitored and could be used to improve performance under adverse weather.
Performance Diagnosis Tool for Arterial Traffic Signals
Authors: Zheng Jianfeng , Liu Henry X. , Misgen Steve , Yu Guizhen
Published: November 2013

Efficient operation of traffic signals is greatly beneficial to drivers. Because of the intensive labor required, most traffic signals in the United States are retimed once every 3 to 5 years or more, even though signal retiming has a very high benefit–cost ratio. Such a practice may miss opportunities for operational improvements and lead to unnecessary delays. One of the major obstacles to improving the practice is the lack of data collection capability and a convenient performance monitoring tool for signalized arterials. To fill this gap, this paper proposes a performance diagnosis tool for arterial traffic signal systems. The tool aims at identifying necessary parameter changes and assisting agencies in periodically fine-tuning signal timing parameters. A flexible and low-cost data collection unit is developed to equip traffic signal cabinets with event-based data collection capability. Three major parameters of traffic signals (offset, green split, and cycle length) are evaluated in the data center by diagnosis modules that use event-based traffic data. The development of the data collection unit and the diagnosis methodologies are described in detail. The implementation of the tool is illustrated by field data analysis at intersections on Trunk Highway 13 in Burnsville, Minnesota.
Statistical Study of the Impact of Adaptive Traffic Signal Control on Traffic and Transit Performance
Authors: Slavin Courtney , Feng Wei , Figliozzi Miguel , Koonce Peter
Published: November 2013

The Sydney Coordinated Adaptive Traffic System (SCATS) is designed to improve mobility on congested corridors with variable demand; SCATS is expected to improve transit performance. Because many urban corridors are heavily used by transit routes, it is important to determine how SCATS affects transit performance on congested corridors. However, there is limited research on evaluating the impact of SCATS on transit performance. To the best of the authors’ knowledge, this research presents the first field evaluation of SCATS with transit signal priority in the United States. The case study is based on before-and-after traffic and transit data along Powell Boulevard, one of the most congested urban arterials in the Portland, Oregon, metropolitan region. Using permanent traffic data collection stations, bus automated vehicle location and automatic passenger count data, and transit signal priority request data, this work presents the results of statistical tests and regressions to determine the impacts of SCATS. Statistically significant differences were observed in travel times and SCATS-related regression parameters. Overall, travel time changes or improvements related to SCATS seemed to depend greatly on the direction of travel and time of day.
Daytime and Nighttime Passing Maneuvers on a Two-Lane Rural Road in Spain
Authors: Llorca Carlos , Moreno Ana Tsui , García Alfredo , Pérez-Zuriaga Ana María
Published: November 2013

Passing is one of the most complex driving maneuvers performed on two-lane rural roads and has important effects on road safety and traffic operation. Passing is affected by driving behavior, road geometry, traffic volume, and traffic composition as well as external factors. Research was developed to compare the passing process under daytime and nighttime conditions. An experimental method was designed to collect video data of passing maneuvers on a two-lane rural road segment located near Valencia, Spain. Two methods were used: (a) external observations of four passing zones with six video cameras and (b) an instrumented vehicle equipped with video cameras and laser rangefinders, driven slightly below the operating speed along a segment of the same road so it would be passed by other vehicles. A total of 291 maneuvers were observed, up to 20% of which were at night. Macroscopic analysis results indicated that approximately 17% of passes were at night, even though passing frequency and passing demand decreased at night. Also, the behaviors of individual drivers who passed other vehicles were different at night and during the day. Maneuvers limited by the presence of an opposing vehicle were performed more quickly at night, even if the accepted gaps were longer. In this case, a more difficult perception of distances to opposing vehicles and of vehicle speeds explained the differences. In contrast, maneuvers limited by sight distance (without a visible opposing vehicle) were slower at night. This observation matched a traditional hypothesis: passing at night is safer because the headlights of an opposing vehicle allow a driver to anticipate the vehicle's position before it becomes visible.
Algorithm for Analyzing Horizontal Sight Distance from Lane Centerline Coordinates
Authors: Azimi Mehdi , Hawkins H. Gene
Published: November 2013

An algorithm for analyzing the availability of horizontal sight distance on two-lane highways to establish the location of no-passing zones is described. The intent was to incorporate the algorithm into a computer model that could use coordinates of a lane centerline as the input and evaluate the availability of horizontal sight distances. The algorithm was applied to develop a method for locating no-passing zones that was more efficient, accurate, and safe than the current methods that require field measurements. The algorithm uses vector product calculations to derive the geometry of the roadway centerline from spatial coordinates of available data points that represent the center of the travel lane. From the roadway centerline definition, the algorithm defines the location of visual clear zone boundaries on both sides of the roadway. Finally, the algorithm uses the roadway centerline and visual clear zone boundary information to determine whether sufficient passing sight distance exists at each point along the centerline.
Roadside Clearance Limit on Horizontal Curves with Transition Arcs
Authors: Mauga Timur , Ghanma Mwafag , Ahmed Kamran
Published: November 2013

AASHTO guidelines for the geometric design of highways require that the insides of horizontal curves be clear of sight obstructions to provide required sight distance. However, the guideline's method for determining minimum roadside clearance is suitable only for middle sections of horizontal curves at sites where the circular arcs are equal to or longer than sight distance. For other sites and sections of horizontal curves, the guideline recommends the use of graphical or computational methods. The graphical method is tedious and time-consuming, and the recommended computational method was prepared for sites with circular arcs equal to or longer than sight distance. An analytical model was developed for clearance offsets for sites with circular arcs shorter than sight distance. Offsets were defined as normal ordinates from the driver path to a curve that demarcates the roadside area that accommodates sightlines. Variables in the model are sight distance, length of transition, length of circular curve, radius of circular curve, and driver location. Design charts for maximum and intermediate offsets were developed for use by practitioners with the model. Offsets from the charts for curves that have transition arcs were significantly shorter than offsets for equivalent simple curves. With these charts, the extra excavation costs associated with the resultant bigger offsets of other models can be avoided. Study results will be of value to engineers involved in design policy, highway maintenance, and design improvement for sites with insufficient sight distance.
Safety Impacts of Design Exceptions on Nonfreeway Segments
Authors: Wood Jonathan S. , Porter Richard J.
Published: November 2013

Safety (in terms of expected crash frequency and severity) was compared on road segments where design exceptions had been approved and constructed and on similar road segments where no design exceptions had been approved or constructed. Data were collected for design exceptions in Utah from 2001 to 2006. Multiple data sources were used to identify and define road segments with and without design exceptions. Propensity scores were applied to assess similarities between treatment and comparison sites. Ultimately, 34 total nonfreeway segments with design exceptions and 80 nonfreeway segments without design exceptions were used for modeling. The relationship between the presence of design exceptions and crash frequency was explored with a negative binomial regression modeling approach. The relationship between the presence of design exceptions and crash severity was explored in three ways: (a) computation of severity distributions at locations with and without design exceptions, (b) estimation of separate negative binomial regression models by severity level, and (c) estimation of multinomial logit models to predict the severity outcome of a crash. The presence of design exceptions was represented in the regression models by an indicator variable (where 1 5 one design exception or more and 0 5 no design exceptions). Crash data from 2007 through 2010 were used for model estimation. No significant differences were observed in expected crash frequencies and crash severities between nonfreeway road segments with and without design exceptions. This overall finding was consistent with two previous related efforts in Kentucky and Indiana.
Decision Tool to Define and Quantify Interchange Complexity
Authors: Brewer Marcus A. , Fitzpatrick Kay , Chrysler Susan T.
Published: November 2013

Because complexity typically is a qualitative characteristic, the ability to evaluate the complexity of an interchange objectively is somewhat difficult. This difficulty is compounded when trying to compare the complex features of multiple interchanges. A spreadsheet-based decision tool that was developed as a method for the quantification and comparison of the complexity of freeway interchanges in the United States is discussed. The initial discussion focuses on the steps that guided researchers in the development of the spreadsheet, and this discussion is followed by a description of the spreadsheet itself and how practitioners can use it to evaluate the complexity of interchanges under their consideration. A review is provided of the results researchers obtained with the spreadsheet in an evaluation of the complexity of 28 existing interchanges in 11 states. These study sites ranged from relatively simple to complex, and results indicated that the spreadsheet-generated scores were generally consistent with researchers’ qualitative estimates of the sites’ relative complexity. The meaning and interpretation of the spreadsheet results are discussed.
Evaluating Traveler Preferences, Values, and Behaviors Associated with Public Rest Areas
Authors: Todd Ryan G. , Gates Timothy J. , Savolainen Peter T.
Published: November 2013

How travelers select and value public rest areas was investigated. A comprehensive survey was conducted at 15 public rest areas throughout Michigan; a similar survey was performed at two large commercial travel centers for comparison purposes. The primary objectives of this survey were to (a) identify the reasons motorists stop at public rest areas versus commercial service facilities, (b) estimate the value of services provided by public rest areas, and (c) determine the probable action taken by motorists in the event that a public rest area was unavailable. Results of the survey indicated that patrons at both public rest areas and commercial service facilities generally preferred rest areas for basic services (e.g., restroom use, short break) primarily because of the convenient freeway access. The median patron-reported value of services at standard public rest areas was $1.68 per stop compared with $2.21 per stop at rest areas that included a traveler information center. Even though drivers of commercial vehicles were the most frequent users of public rest areas, they tended to be less satisfied and gave a lower value to services provided. Had a particular public rest area not been available, approximately two-thirds of travelers in private vehicles would have diverted off the freeway to a commercial service facility, whereas one-quarter would have continued to the next rest area along the route. Commercial truck drivers were equally likely to continue to the next rest area as to divert off the freeway.
Context-Sensitive Approach for Network Selection of Infrastructure Projects
Authors: Cafiso Salvatore , Di Graziano Alessandro , Stamatiadis Nikiforos
Published: November 2013

Context-sensitive solutions (CSS) aim to provide a systematic, comprehensive approach to project development from inception and planning through operation and maintenance. The goal is a procedure that provides an outcome that harmonizes transportation requirements with community needs and values. Multicriteria analysis can assist in the assessment of competing needs and provide a systematic approach to evaluation of the options. The CSS approach and multicriteria analysis were merged in an implemented procedure to select the most effective investment projects for solving a classical multiobjective optimization problem under budget constraints. The potential of this procedure was explored, and the steps required to evaluate this concept were identified. A case study was used to demonstrate the process and to identify future steps to ensure widespread application of the process.
Project Emission Estimator
Authors: Mukherjee Amlan , Stawowy Brian , Cass Darrell
Published: November 2013

Motivated by the need to address the challenges of global climate change, this paper develops and implements a project-based life-cycle framework that can be used to estimate the carbon footprint for typical construction work items found in reconstruction, rehabilitation, and capital preventive maintenance projects. Through applying existing life-cycle assessment methods and inventories, the proposed framework considers the life-cycle emissions of products and processes involved in the raw material acquisition and manufacturing phase and in the pavement construction phase. The framework also estimates emissions from vehicular use and maintenance operations during the service life of the pavement. The Project Emission Estimator (PE-2), a web-based tool that implements the project-based life-cycle framework, can be used to benchmark the carbon dioxide (CO2) footprint of highway construction projects. This paper suggests ways contractors and state transportation agencies can implement the PE-2 to benchmark and help reduce the CO2 footprints of highway construction projects.
Toward Sustainable Pavement Management
Authors: Faghih-Imani Ahmadreza , Amador-Jimenez Luis
Published: November 2013

Transportation asset management systems are concerned with the daunting task of maintenance and upgrade of infrastructure within the restrictions of an annual budget. Consideration of environmental impacts is normally left out of the analysis. This paper considers the incorporation into strategic planning of environmental impacts resulting from maintenance and rehabilitation of pavements. The energy use of such activities and resulting greenhouse gas (GHG) emissions are explicitly considered, and the results of a performance-based optimization are discussed. The study followed a three-step trade-off process: (a) finding the minimum requirement for the annual budget, (b) maximizing pavement condition, and (c) reducing environmental impacts. The results showed that considering environmental impacts in the strategic planning process returned a substantial gain in energy savings and reduction of GHG emissions, although a small sacrifice in pavement performance was required. The consideration of environmental impacts reduced energy use and GHG emissions by 19% and 24%, respectively, but pavement condition dropped slightly to 98.5% of the optimal solution.
Bayesian Approach to Updating Markov-Based Models for Predicting Pavement Performance
Authors: Tabatabaee Nader , Ziyadi Mojtaba
Published: November 2013

The Markov decision process is one of the most common probabilistic prediction models used in infrastructure management. When existing data are insufficient, expert knowledge is commonly used to derive a Markovian transition probability matrix. Eventually, every pavement management system will progress to a level at which inspection measurements from the network will be organized into a database to be used for performance prediction. The best way to use this body of data to improve the initially developed transition probability matrix is to combine prior expert knowledge with new observations. This paper proposes a method for periodically updating Markovian transition probabilities as new inspection data become available. Bayesian inference is used to accommodate uncertainty in the expert-derived initial probabilities and measurement errors from inspection of the network. A data set of asphalt concrete pavement observations from the Minnesota Department of Transportation test facility is used to illustrate the proposed method.
Findings from the International Scan on Managing Pavements and Monitoring Performance
Authors: Zimmerman Kathryn A. , Corley-Lay Judith , Wlaschin J. B. (Butch) , Tetreault Richard M.
Published: November 2013

Nine pavement and asset managers from the United States participated in the International Scan on Managing Pavements and Monitoring Performance. The scan team sought input on processes for implementing sustainable performance-based programs; effective communication methods for garnering upper management and legislative support; agency cultures that support performance-based programs; and techniques, tools, analyses, and reporting that support performance-based management. The team traveled to New Zealand, Australia, Sweden, the Netherlands, and England and gathered information from 14 agencies. The agencies selected for consultation had experience with managing their pavement networks under constrained budgets. Although the initial focus of the scan was on pavement management, the team found that some of the agencies conducted pavement management within an asset management framework. The findings are thus equally applicable to assets other than pavements. The key findings are (a) agency culture supports a long-term view toward managing pavements, (b) elected officials understand their responsibilities as stewards of public funds, (c) the road network is managed as a service provided to the traveling public, (d) agency priorities are known and agency personnel are held accountable for their actions, (e) the agencies recognize the importance of building internal capacity and capabilities, and (f) efficiency and value drive program delivery approaches. The scan team selected four implementation strategies for moving scan findings into practice: communicating scan findings, developing guidelines for asset management plans and long-term financial plans, encouraging use of recurring program assessments, and developing agency capabilities in the areas of engineering, contract administration, economics, and accounting.
Evaluating Pavement Condition of the National Highway System
Authors: Simpson Amy L. , Rada Gonzalo , Visintine Beth , Groeger Jonathan L.
Published: November 2013

FHWA recently conducted a study to identify a means for evaluating the health of the Interstate highway system, with a specific focus on pavements and bridges. One important component of any statement of health is the condition of the pavement, which is the focus of this paper. Data on an 874-mi long corridor of I-90 were used to review the potential of a set of six metrics for evaluating pavement condition as good, fair, or poor across the Interstate network. The metrics reviewed included both functional and structural pavement condition. The study concluded that currently the international roughness index provides the most consistent method for evaluating ride quality. Other metrics, which use distress or structural condition to evaluate pavement, are not currently suitable as measures of nationwide condition and will require further work before they can be implemented for routine use.
Management of Pavement Maintenance, Rehabilitation, and Reconstruction through Network Partition
Authors: Gao Lu , Zhang Zhanmin
Published: November 2013

This paper presents a new optimization model for addressing the problem of planning pavement maintenance, rehabilitation, and reconstruction (MRR) for a large-scale road network. In the past, this problem has usually been formulated as a linear programming or integer programming model. The solutions obtained from those models determine the timing, location, and type of treatment needed to perform the MRR operation for a given planning horizon. A shortcoming of such models is that the sections selected for MRR are usually distributed spatially across the network, and this distribution makes it difficult to plan and implement MRR activities in a coordinated manner. To take advantage of economies of scale, adjacent road sections with similar MRR needs should be maintained within a single project. However, the idea of automatically combining adjacent sections into one large project has not been given serious attention in existing optimization models for pavement MRR planning. This paper proposes a new approach to pavement MRR planning that utilizes the spatial structure of the road network. The road network is first partitioned into groups of adjacent sections, or MRR projects, with similar MRR needs. Then a knapsack problem is solved to optimally allocate resources to selected MRR projects with the objective of maximizing system performance.