bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Procurement of Architectural and Engineering Services for Public Works: Case for Qualifications-Based Selection
Authors: Christodoulou Symeon
Published: April 2007

The findings of a recent study on the procurement of professional architectural and engineering (A/E) services in New York City are outlined in an attempt to evaluate some of the claims put forward by proponents and opponents of qualifications-based selection (QBS) of such services. QBS is a federally mandated requirement enacted by the U.S. Congress in 1972, in recognition of the need for improvements in the way in which professional A/E services are procured. The law, commonly referred to as the "Brooks Act," requires that architects and engineers be selected on the basis of their professional qualifications and subject to negotiation of a fair and reasonable compensation of such services. New York State is one of the states that adopted QBS (a total of 41 states had adopted it as of the end of 2001); but the New York State law does not cover local jurisdictions, and New York City continues to use competitive pricing as its primary method of selecting A/E contractors, citing the numerous advantages of the current system as well as the disadvantages of the proposed QBS method. The present study was based on past literature as well as recently procured projects in New York City (1997 to 1999), as presented by the New York City Mayor’s Office of Contracts during a public hearing on QBS (December 1999).
New Font and Arrow for National Park Service Guide Signs
Authors: Garvey Philip M. , Chirwa Kingston N. , Meeker Donald T. , Pietrucha Martin T. , Zineddin Abdulilah Z. , Ghebrial Ramy S. , Montalbano James
Published: April 2007

Although highly legible, the National Park Service's (NPS) Clarendon font produces sign legends that can be 10% to 20% longer than those depicted in conventional sans serif fonts. Placing these wider signs on narrow park roads and in urban historic districts can be prohibitive. To address this problem, a project was initiated to create a new NPS Roman-style (i.e., serif) font that requires less horizontal sign space than Clarendon while improving sign readability and retaining Clarendon's unique "signature quality." The present study also evaluated a set of guide sign arrows to select the most legible for use on NPS guide signs. Three candidate typefaces were developed for daytime and nighttime field evaluation with 72 older and younger subjects. From the results of the evaluation, a fourth font was created and field tested with 12 additional subjects. Words created with the fourth font (NPS Roadway) were 5% to 11.5% shorter than those created with Clarendon. Further, subjects were able to read these words at 10.5% longer average threshold legibility distances than the same words composed in Clarendon. The relative legibility of 12 candidate guide sign arrows was evaluated in an outdoor field study. Forty-eight subjects participated in the daytime, and 32 subjects viewed the arrows at night. There were statistically significant differences in legibility distance among the various arrow shapes. The arrow ultimately recommended for use on NPS road guide signs performed 18% better than the FHWA "standard arrow".
Driver Behavior Characteristics at Urban Signalized Intersections
Authors: Schattler Kerrie L. , Datta Tapan K.
Published: April 2007

Red-light running and the associated risk of severe crashes at signalized intersections have been an ongoing concern to many safety professionals. The proportions of crashes that occur due to such driver behavior represent a substantial number of crashes at urban and suburban signalized intersections in Michigan. In the year 2001, crashes related to red-light running in Michigan represented about 28% of the crashes of all severities and 40% of fatal and serious injury crashes occurring within signalized intersections. Many initiatives to discourage red-light running have been used in the United States with various degrees of success. Such programs include public awareness campaigns, automated enforcement programs, and some engineering countermeasures. These initiatives have resulted in some reduction in the overall crash statistics in the communities where such programs have been implemented. A series of evaluation studies was performed in Michigan to test the effectiveness of implementing change and clearance intervals calculated according to ITE guidelines on late exits and red-light violations at nine signalized intersections in the Detroit metropolitan area. The study described used four approaches at four test intersections where engineering treatments have been applied (16 total test sites) and four approaches at five control intersections. Driver behavior was examined at test and control intersections by observing and quantifying the number of vehicles that did not clear the intersection when the cross-street signal light turns green (late exit) and red-light violations. Upon analysis, red-light-running data at the test and control sites did not exhibit a significant difference. However, the test sites showed significantly lower late exit rates compared with the control sites, thus lowering the risk of right-angle crashes.
Safety Evaluation of Centerline Rumble Strips: Crash and Driver Behavior Analysis
Authors: Noyce David A. , Elango Vetri Venthan
Published: April 2007

The effectiveness of centerline rumble strips in reducing cross-over-the-centerline crashes and improving the safety of undivided roadways was evaluated. Twenty U.S. states, along with several Canadian provinces, are currently using centerline rumble strips. A detailed analysis of crashes on State Routes 2,20, and 88 in Massachusetts before and after installation of centerline rumble strips showed no significant change in crash frequencies; however, no fatal crashes have occurred on State Routes 2 and 88 since the installation of centerline rumble strips. Three cross-over-the-centerline fatal crashes did occur on State Route 20 after the centerline rumble strips were installed; centerline rumble strips were not a countermeasure to these specific crash types. Driver behavior at shoulder and centerline rumble strips was evaluated with a full-scale driving simulator. Drivers were found to react and correct the vehicle trajectory more quickly with centerline rumble strip encounters than with shoulder rumble strip encounters. About 27% of drivers made an initial leftward correction of their vehicles when encountering centerline rumble strips. Although this percentage may be inflated because of laboratory conditions, there is some probability of a driver confusing centerline rumble strips with shoulder rumble strips and reacting improperly. No improper (rightward) corrections were experienced with shoulder rumble strip scenarios. Centerline rumble strips were found to be effective at gaining drivers' attention and therefore to be an effective traffic control device and safety countermeasure in areas where a history of cross-over-the-centerline fatal and injury crashes occur.
Field Evaluations of Warning and Regulatory Signs with Enhanced Conspicuity Properties
Authors: Gates Tim J. , Carlson Paul J. , Hawkins H. Gene
Published: April 2007

Researchers examined the impacts of various sign conspicuity enhancements on traffic operations and driver behavior in Texas. Eight types of applications were evaluated: fluorescent yellow chevrons, fluorescent yellow chevron posts, fluorescent yellow curve signs, fluorescent yellow ramp advisory speed signs, fluorescent yellow stop ahead signs, fluorescent red stop signs, flashing red light-emitting diode (LED) stop signs, and a standard red border on speed limit signs. Fourteen sites were used for the evaluations. Traffic operations data collected before and after the sign upgrades included vehicle speeds, edge line encroachments, and stopping compliance. Many statistically significant beneficial results occurred, including the following: fluorescent yellow chevron signs produced a significant reduction in curve speeds and edge line encroachments, both the fluorescent red and LED stop sign treatments reduced the number of vehicles not fully stopping, and the standard red reflectorized border on the speed limit sign produced a significant improvement in speed limit compliance. The data showed no undesirable impacts for the measures of effectiveness for any of the signing treatments. On the basis of the findings, the researchers recommend fluorescent yellow chevrons for full implementation. The other fluorescent yellow signs evaluated in the research are recommended for implementation on an as-needed basis. Microprismatic stop signs and flashing LED stop signs are also recommended for implementation on an as-needed basis. Although found to be effective, the red border speed limit sign currently should be limited to experimental implementation, as permission is required from FHWA to install these signs. The fluorescent red stop sign is not commercially available at this time.
Extended Photometric Model of Fog Effects on Road Vision
Authors: Dumont Eric , Cavallo Viola
Published: April 2007

The road environment projects a luminance distribution into the eyes of the driver. In the presence of fog, the resulting visual signal is disturbed because of light scattering by airborne water droplets. This phenomenon has three major effects, which cause an overall visibility loss: attenuation, halo, and veiling. Koschmieder's law is widely used to describe how fog modifies the visual signal, but it applies only when nonluminous objects are being observed in daytime. In nighttime and with self-luminous objects, luminance from scattered light can no longer be neglected. The optical mechanisms underlying the visual effects of fog have been analyzed. Koschmieder's law was then extended to account for halos and backscattered veil in the disturbed visual signal. The utility and validity of the resulting photometric model were discussed, and an example was provided that illustrates how it can be used to predict the image of a foggy road environment as seen by a driver. Despite its complexity, the model should find many applications, such as driving simulation and aiding device design.
Visual Performance Under Mesopic Conditions: Consequences for Roadway Lighting
Authors: Bullough John D. , Rea Mark S.
Published: April 2007

Mesopic vision corresponds to luminances in which both the rods and cones contribute to vision. Many light levels for roadways, parking lots, and other exterior locations result in luminances within the mesopic vision region. Research is summarized that shows that the potentially large magnitude of spectral effects under mesopic conditions cannot be predicted from orthodox models of visual response without additional information about the contrast, size, and context of a visual stimulus. If peripheral detection is a relevant visual task for a roadway lighting installation that operates at mesopic conditions, then characterizing light levels in terms of photopic luminous efficiency, as is conventionally done, will not properly characterize the effectiveness of those light levels for this response. Consideration of the visual periphery can result in different selection of light sources than would result from a consideration of on-axis vision alone.
Laboratory Evaluation of Intrusion Detection Technologies for High-Speed Rail Grade Crossings
Authors: Zaworski J. R. , Hunter-Zaworski K. M.
Published: April 2007

The rail industry is in the process of developing a prototype system for high-speed rail. One of the concerns associated with high-speed rail is the danger posed by obstructions on the track. This level of danger is much higher than with traditional railway vehicles because the highspeed passenger equipment is both lighter and faster moving than traditional equipment. Therefore, it is more vulnerable to serious damage and derailment by objects on the track. Two existing traffic monitoring technologies were considered to have potential for railway intrusion detection: video systems and microwave systems. Qualitative laboratory tests were conducted on each system to evaluate the ability to detect objects as a function of size, material, color, and entry direction. Quantitative tests were conducted to define the capability of each type of system to detect objects as a function of object size. Test results indicate that both systems have good potential for use in railroad intrusion detection. The video system was tested in indirect natural light, medium-intensity artificial lighting, and low-level artificial lighting. Object detection was independent of color, composition, and direction of entry but was a direct function of detection zone size. Spheres as small as 4 in. in diameter were detected consistently. The microwave system would consistently detect 4-in. spheres, and results were independent of material, color, entry direction, and zone size. It was concluded that existing video- and microwave-based traffic monitoring systems have potential for use in a railroad intrusion detection application and that field tests should be pursued.
Direct Fixation Track Design
Authors: Daniels Laurence E.
Published: April 2007

Design principles for direct fixation track must address a wide range of parameters and issues. Described are the basic design principles related to loading and how they are applied for direct fixation track. There is a presentation of the principles and methods for determining loads imposed on fasteners for an application, determining fastener spacing, determining anchor bolt and insert characteristics (shear strength, pull-out strength), and implementing the fastener support design. Additionally, design approaches that improve construction with reduced costs, fundamental stipulations that should be included in direct fixation construction specifications, and direct fixation track tolerances (mating tolerances, construction tolerances) are addressed. Although the principles apply to any direct fixation system, the study concentrates on track systems using fully bonded fasteners with elastic rail clips, a common arrangement. A useful reference is proposed for analysis of existing installations as well as new installations.
Mileage-Based Road User Charge Concept
Authors: Forkenbrock David J.
Published: April 2007

A new approach is presented for charging vehicles that travel on public roadways. This approach applies intelligent transportation system technology to the problem of assessing road user charges, enabling these charges to be fairer, more stable, and more flexible. The approach is amenable to alternative forms of vehicle propulsion systems. Though very simple in concept, the new approach has required that a number of institutional and technological issues be resolved. Key to this approach is a simple onboard computer that stores a record of actual road use charges. Periodically this record is uploaded and transmitted to a data processing center, referred to as the collection center. The center bills a vehicle owner and reimburses the states, counties, and cities operating the roads on which the vehicle has traveled. The onboard system is simple, secure, and capable of protecting the user's privacy. Importantly, the onboard system enables a variety of user charge conventions. In its simplest form, this approach can be used to assess a vehicle-miles-traveled (VMT) user charge. With a VMT user charge, the computer can calculate road mileage actually traversed and compare this mileage with that obtained through an odometer feed. It then applies appropriate user charge rates to the mileage traveled in each jurisdiction.
Examination of Houston's QuickRide Participants by Frequency of QuickRide Usage
Authors: Burris Mark W. , Appiah Justice
Published: April 2007

QuickRide is an innovative project designed to more effectively use the capacity of the high-occupancy-vehicle (HOV) lanes on the Katy (I-10) and Northwest (US-290) freeways in Houston. Under this project, two-person carpools could pay $2 to use the HOV lanes during the peak period, even though the lanes were normally restricted to vehicles with three or more occupants. This form of HOV lane is typically termed a high-occupancy toll (HOT) lane and can be an effective travel demand management and congestion mitigation tool. However, relatively little is known about drivers who choose to use the HOT lane option. The commute and socioeconomic characteristics of Houston's QuickRide participants are examined by their frequency of QuickRide usage. The study is based on a survey of QuickRide enrollees conducted in March 2003. It was found that QuickRide participation increases with increasing trip length, perceived time savings, and frequency of trips in the travel corridor. Participation decreases with increasing carpool formation times but is generally irresponsive to minor changes in the $2 toll. QuickRide is also more likely to be used for commute trips than other trips. Socioeconomic characteristics such as age, household type, and education also have significant effects on QuickRide trip frequency. However, household size, occupation, and hourly wage rate were not good indicators of the frequency of QuickRide usage.
Benefit-Cost Analysis of State Highway Program as a Whole: Conceptualizing the Null Alternative
Authors: Burress David , Oslund Patricia
Published: April 2007

Benefit-cost analysis (BCA) of highway projects is usually based on comparisons with a null or no-build alternative. More generally, any meaningful BCA must compare whatever is being evaluated with a reasonably complete and well-defined alternative state of affairs, sometimes referred to as the counterfactual world. The analysis, specification, and modeling of the counterfactual world used in a retrospective BCA of the Kansas Comprehensive Highway Program (1989-1997) are described. Retrospective BCA for a state highway program as a whole raises important issues not addressed in previous literature. Generally, the policy client is concerned with state impacts, not national impacts. Also, a benefit-cost ratio (BCR) is much more useful to policy makers concerned about future programs than is net present value. Unfortunately, measured BCRs are sensitive both to choice of counterfactual world and to conceptualization of costs versus negative benefits. Benefit-cost literature increasingly emphasizes the importance of documenting a well-defined counterfactual alternative. That is important because the net benefit of a project (i.e., benefit less cost) equals the sum of valuations of all differences between the actual world and the counterfactual world. Hence, in the absence of the counterfactual, the BCR is not well defined. A model for these concepts is provided, and the relationship to opportunity cost is clarified. The specific counterfactual used in the Kansas study is then described.
Role of Transportation in Regional Economic Efficiency in Bangladesh: Data Envelopment Analysis
Authors: Alam Jobair B. , Sikder Saiyid H. , Goulias K. G.
Published: April 2007

In Bangladesh the investment patterns and criteria under which resources are allocated among competing sectors and projects may have created an imbalance in the distribution of investment among production factors as well as among regions, resulting in economic inefficiency. For this reason, the role of transportation investment in the regional economic development of Bangladesh is examined in detail. The data envelopment analysis (DEA) technique is used to examine the technical efficiency of investment in transportation infrastructure development for each region of the country. Investment in infrastructure development of the less-efficient regions is found to be more effective by providing a higher rate of return. DEA is used to identify investment priorities for specific regions, and their relative impacts are assessed. It is shown that future transportation investment should focus on peripheral regions; for the rest of the country, industrial investment is found to be more beneficial.
Analysis of the Effects of Speed Limit Enforcement Cameras: Differentiation by Road Type and Catchment Area
Authors: Hess Stephane
Published: April 2007

A detailed statistical analysis is presented of the effects of speed limit enforcement cameras on injury accident numbers. The approach used is constructed in such a way that it is possible to differentiate not only between the effects of the cameras and the effects of trend and seasonality but actually to produce estimates that are independent of any other overall time-dependent effects. Crucially, the estimates produced are also net of the effects of regression to the mean. To allow for the simultaneous treatment of the different levels of severity, weights are used that reflect the frequency of the different types of accidents. This approach is then used on a data set for all injury accidents in Cambridgeshire between 1990 and 2002, which also contains data from 49 camera sites. To quantify the range of effectiveness of the cameras, estimates of the changes in accident numbers are produced for different distances from the camera site. The analysis shows that, overall, in the immediate vicinity of the camera sites, the installation of a camera can be expected to lead to decreases in weighted injury accident numbers by an astounding 45.74%. Lower, but still significant, decreases are observed in the wider surrounding area. Finally, to provide further insight into the differences in performance on different road types, the sites are grouped together according to road category. This analysis shows that the biggest reduction in accident numbers can be obtained on roads with a higher incidence of speeding offenses.
Evaluating the Insurance Corporation of British Columbia Road-Safety Improvement Program
Authors: Sayed Tarek , deLeur Paul , Sawalha Ziad
Published: April 2007

The Insurance Corporation of British Columbia (ICBC) has been involved in the investment of road infrastructure improvement for many years, delivering an annual program known as the Road Improvement Program. Corporation staff realized that selective road improvement projects have tremendous potential to improve road safety performance. This improved road safety performance, measured in terms of a reduction in the frequency and severity of collisions, also led to a reduction in the cost of automobile insurance claims. This reduced claim cost provided the basis for the economic justification for investments in road infrastructure improvements. To ensure that the justification for the ICBC investment in road safety improvements is verified, a formal evaluation of the Road Improvement Program is undertaken at regular intervals. However, conducting a thorough and reliable evaluation of road safety projects can be difficult and involves significant effort. Presented are details of the important factors that should be considered when conducting an evaluation of road safety improvement projects. The methodology and results used to perform the latest ICBC program evaluation are described.
Review of Procedures Associated with Devising Emergency Evacuation Plans
Authors: Alsnih Rahaf , Stopher Peter R.
Published: April 2007

The incidence of freak weather and geological events, such as earthquakes and volcanic eruptions, has increased over the past 30 years. Coupled with an increase in the populations located in the path of these natural disasters, the imminent danger posed by naturally occurring phenomena has also risen. Given the potential dangers, it is wise for policy administrators to ensure that appropriate emergency plans are in place that aim to minimize the negative consequences associated with these disasters. Effective emergency planning and management should successfully combine the skills and knowledge of law enforcement agencies and transport planners as well as the knowledge and skills of emergency planning professionals. In Australia, there has not been a thorough investigation of the emergency impacts on the transport infrastructure nor have emergency plans adequately integrated the transportation aspect. Which transport routes evacuees and emergency vehicles should use is a question that needs to be answered urgently to avoid situations where evacuees are trapped in their vehicles; in which emergency personnel are unable to gain access to the people in need; and in which emergency vehicles are not able to get onto the road network due to traffic congestion. Thus, in a case of a suburban bushfire (wildfire), a fire that may have been easily extinguished or controlled is left to engulf more bushland and increase in ferocity. The many emergency evacuation models developed are critically assessed, and the important information required to devise the models is described. It is clear, however, that more research needs to be undertaken to investigate specifically the effects of a mass evacuation on current transport networks.
Thin Maintenance Surface Treatments: Comparative Study
Authors: Jahren Charles T. , Behling Kevin R.
Published: April 2007

Thin maintenance surfaces (TMSs) provide an economical method of extending pavement life for asphaltic concrete or bituminous roads. Two phases of research were undertaken to demonstrate TMSs and establish guidelines for their use in Iowa. The project involved the construction and observation of multiple test sections on four rural U.S. highways in Iowa over a 3-year period. Average annual daily traffic on these highways ranged from approximately 1,000 to 5,000. Test sections included single and double chip seals with various types and sizes of aggregates and two types of binder: cationic emulsion and high-float emulsion. Test sections of microsurfacing, microsurfacing cape seal, and thin-lift hot-mix overlay were also placed. These TMS treatments were compared with control sections. Researchers designed the chip seal test sections, monitored the construction process, and collected quality-control information on materials. The pavement condition index (PCI) and skid resistance were measured and compared for each test section before and after construction. TMSs improved PCI when materials were selected properly and quality construction techniques were used. Success was achieved with chip seal that used graded cover aggregates and small cover aggregates and also with various thin-lift overlays. Difficulties were experienced with microsurfacing aggregates that had few fines. The results of the study reinforce the importance of selecting the right type of TMS, ensuring construction quality, and having favorable weather during and after construction.
Bridge Deck Management System with Integrated Life-Cycle Cost Optimization
Authors: Hegazy Tarek , Elbeltagi Emad , El-Behairy Hatem
Published: April 2007

Bridge management systems can be classified as one of two types: network level or project level. The former type is concerned with the prioritization of bridges for inclusion in an upcoming maintenance, repair, and rehabilitation program, and the latter focuses on the repairs that suit the components of a selected bridge. Even though these types are interrelated, most bridge management research treats them as separate aspects. A comprehensive framework is presented for a bridge deck management system that aims at integrating project-and network-level decisions into a unified model to optimize costs at both levels. The novelty of the proposed approach stems from three main aspects: incorporating project-level repair options along with their performance improvements and cost implications; incorporating many flexible and practical features such as variable yearly budget limits, variable yearly discount rates, and optional methods for handling project-level repairs (e.g., single or multiple visits); and using a powerful genetic algorithm-based optimization to consider both project- and network-level variables into bridge life-cycle cost optimization. The proposed model and its implementation are described, and an example application is presented. Although this research focuses on bridge decks, details on future improvements to incorporate all bridge components are outlined.
Overlay Types Used as Preventive Maintenance on Tennessee Bridge Decks
Authors: Knight Marcus L. , Wilson G. Scott , Seger Wayne J. , Mahadevan Sankaran
Published: April 2007

Of all the components that compose a highway bridge, the bridge deck usually deteriorates the most quickly and requires the most maintenance and repair because of its exposure to detrimental conditions. Several preventive maintenance techniques are available to retard bridge deck deterioration and thus prolong service lives. Of these techniques, types of bridge deck overlays are investigated. As preventive maintenance, an overlay provides a protective layer between the bridge deck and the detrimental conditions that promote deterioration. In general, this protection enhances the material properties of the overlay, which may include low permeability and resistance to chemical attack as well as added thickness. The overlay procedures used for bridge decks in Tennessee are investigated from information about overlay types and their usage obtained through several sources, including interviews with Tennessee Department of Transportation personnel who are experienced in bridge maintenance. Four types are identified: asphalt, reinforced portland cement concrete, nonreinforced polymer-modified concrete, and thin bonded overlays. Each overlay is described and typical applications, bridge deck preparation, general construction techniques, special considerations, expected service lives, and average costs are discussed. Expected service lives ranged from 15 to more than 30 years, and average costs ranged from $30 to more than $100 per square yard. All overlay types are useful and appropriate under different situations.
Training Neural Networks to Detect Freeway Incidents by Using Particle Swarm Optimization
Authors: Cheu Ruey Long , Srinivasan Dipti , Loo Wee Hoon
Published: April 2007

Among the many models and techniques developed to automatically detect freeway incidents in recent years, the multilayer feed-forward neural network (MLF) is one of the most promising models in terms of high detection rate, low false alarm rate, and faster mean time to detection. The use of particle swarm optimization (PSO) algorithms to train MLFs to detect freeway incidents is investigated in an attempt to further improve detection performance. Several MLFs have been trained by different variations of the PSO methods using real incident data from Interstate 880 in California. The best MLFs were compared with one trained by the conventional backpropagation (BP) algorithm. The evaluation discussed, based on I-880 data, shows that the MLFs trained by the PSO algorithms have the same or higher detection rates, similar or lower false alarm rates, and faster mean time to detection than the MLF trained by the BP algorithm. This research has shown that PSO has the potential to improve the good incident detection performance of the MLF.
Assessment of the Impact of Incidents near Bottlenecks: Strategies to Reduce Delay
Authors: Menendez Monica , Daganzo Carlos
Published: April 2007

How the location and duration of an incident affect delays near a recurrent bottleneck is evaluated in this study. With conventional kinematic wave theory and some dimensional analysis, tools are provided to determine whether an incident will cause generalized delays (i.e., delays that have a lingering effect for the whole length of the peak hour) according to the incident's magnitude, location, and duration. The results apply to a broad range of cases, encompassing many types of facilities and incidents. Furthermore, the results can be used as a foundation for developing and implementing new strategies to obtain significant reductions in delay. The value of fault-free surveillance is also analyzed and presented as part of an optimization problem for locating roadside assistance vehicles. It is found that this value is very high, which could justify installing advanced traffic-monitoring schemes near major bottlenecks.
Sampling Strategies for Probe-Vehicle-Based Freeway Incident Detection Algorithms
Authors: Cheu Ruey Long , Tay Germaine Chi Wen
Published: April 2007

Different sampling strategies are investigated in terms of percentage of vehicles sampled as probes and three methods of aggregating probe-vehicle data for freeway incident detection. The incident detection algorithm is based on the statistical comparison of the average section travel times of two different groups of probe vehicles. A microscopic traffic simulation model was employed to simulate incidents and collect section travel time data from probe vehicles for evaluation of the sampling strategies. Five probe-vehicle percentages were investigated. For each, the probe-vehicle section travel times were aggregated using three different methods: fixed sample size (FSS), fixed time interval (FTI), and rolling interval. Incident detection performance was analyzed in terms of detection rate (DR), false alarm rate (FAR), mean time to detection (MTTD), number of algorithm applications, and number of false alarms. It was found that the FTI data aggregation method performed best for all the indicators when the probe-vehicle percentage was less than 20. When the probe-vehicle percentage exceeds 30 and both FSS and FTI data aggregation methods have high DRs, the FSS method gave the lowest FAR and the FTI data aggregation method produced the lowest number of false alarm cases and fastest mean time to detection. All three data aggregation methods showed similar performance when the probe-vehicle percentage ranged between 20 and 30.
Evaluation of Toll Plaza Performance After Addition of Express Toll Lanes at Mainline Toll Plaza
Authors: Klodzinski Jack , Al-Deek Haitham M.
Published: April 2007

Conversion of a conventional toll plaza to an open-road tolling design with express electronic toll collection (ETC) lanes improved operating conditions for cash and ETC customers during the peak a.m. and p.m. periods. Data were analyzed before and after the plaza's renovation to evaluate its performance. Vehicle delay was not excessive at the plaza during the before-study analysis except for heavy demand during the p.m. peak southbound partly because of a reduction in available service lanes. The typical average delay per cash-paying vehicle was 14 s. After the redesign, the analysis showed a reduction in the average delay per vehicle of 7 s for the automatic coin machine (ACM) lanes and 8 s for the manual cash payment lanes. The average delay per lane per hour was reduced by over 4,560 s for the ACM lanes and 3,360 s for the manual payment lanes. Reduction in total plaza delay for cash customers averaged more than 20 s/veh in the after study. ETC use in the cash payment lanes previously averaged over 10% and dropped below 3% during the a.m. peak. For the exception of the ACM lanes during the p.m. peak northbound, the overall ETC use in the cash lanes was now less than 5%, showing the benefit recognized by ETC users at the plaza from express lanes. During the before study, the plaza capacity in the peak direction during a peak hour was estimated at a maximum of 5,624 vehicles per hour. After implementation of open-road tolling, the estimated capacity increased by 43.8%.
Research Needs for Weather-Responsive Traffic Management
Authors: Pisano Paul A. , Goodwin Lynette C.
Published: April 2007

In weather-responsive traffic management, weather events are viewed as nonrecurring incidents that can be predicted and observed and have effects that can be mitigated. Weather impacts on traffic flow are reported, and an emerging concept of operations for a systemwide approach to traffic management in adverse weather is described. This approach is structured to assess weather impacts and implement operational strategies that improve safety, mobility, and productivity. Finally, research needs to advance the state of the practice in weather-responsive traffic management are enumerated.
Optimization of Time-of-Day Breakpoints for Better Traffic Signal Control
Authors: Park Byungkyu (Brian) , Santra Pinaki , Yun Ilsoo , Lee Do-Hoon
Published: April 2007

Traffic signal control is one of the most cost-effective means of improving urban mobility. Signal control can be categorized as pretimed, actuated, and adaptive. Among these, both pretimed and coordinated actuated controllers deploy multiple signal timing plans to account for traffic demand changes during the day, whereas adaptive control changes the timing plan in real time according to traffic conditions. In the case of pretimed and coordinated actuated signals, morning peak traffic would differ from that of the off-peak such that it would be better to use two distinctive signal timing plans. Traffic engineers often determine such time-of-day (TOD) breakpoints manually by using 1 or 2 days' worth of traffic data. A few recent studies developed statistical and heuristic methods for TOD breakpoints by using archived traffic data. These approaches determined the breakpoints through minimization of within-cluster distance and maximization of between-cluster distances. Thus, the clusters do not directly reflect the performance of timing plans and often result in only local optimal TOD breakpoints. One method is based on a genetic algorithm (GA) that optimizes TOD breakpoints with explicit consideration of signal timing performance at a representative intersection. The proposed method implements two-stage optimizations: outer loop for TOD breakpoints and inner loop for timing plans of corresponding intervals. The proposed approach is implemented on a network consisting of three coordinated actuated signalized intersections. The convergence graphs of both inner-and outer-loop optimization indicate that the GA-based algorithm obtains breakpoints within a relatively small number of iterations. Also studied was the performance of the proposed approach for a varying number of breakpoints (i.e., four to eight). The results, based on a microscopic simulation program, Sim Traffic, indicated that six breakpoints outperformed the other numbers of breakpoints considered.
Transit Buses as Traffic Probes: Use of Geolocation Data for Empirical Evaluation
Authors: Bertini Robert L. , Tantiyanugulchai Sutti
Published: April 2007

With the growing availability of data because of the deployment of intelligent transportation systems, methods for assessing and reporting traffic characteristics and conditions have begun to shift. Although previous level-of-service methods were developed for use with limited data, actual performance measures can now be developed and tested. On freeways, performance measures often are estimated directly by using data from inductive loop detectors (e.g., speed, occupancy, vehicle counts). For arterials with numerous signalized intersections, performance measures are more challenging because of more complicated traffic control and many origins and destinations. However, within signalized networks, travel time, speed, and other key performance measures can be obtained both directly and indirectly from sources such as automatic vehicle location (AVL) data. The use of AVL data for characterizing the performance of an arterial is demonstrated. First, data are extracted from the bus dispatch system of the Tri-County Metropolitan Transit District (TriMet), the transit provider for Portland, Oregon. Then, the performance characteristics as described by bus travel on an arterial are compared to ground truth data collected by probe vehicles equipped with Global Positioning System sensors traveling with normal (nontransit) traffic on the same arterial on the same days. Comparisons are made between the two methods, and some conclusions are drawn regarding the utility of the transit AVL data.
Using Floating Cars to Measure Travel Time Delay: How Accurate Is the Method?
Authors: Wang Zhongren
Published: April 2007

In practice, partial floating car runs (runs in the direction of the traffic flow of interest) plus a measured or assumed controlling bottleneck capacity could be used to estimate the total travel time delay along a freeway segment. The floating car's travel time in excess of that of user-specifiedfree flow travel is defined as the floating car's measured travel time delay. This delay, along with the bottleneck capacity, could be used to estimate excess traffic demand. The total freeway segment delay could then be determined on the basis of the fundamental queuing diagram. To examine the quality of this estimation method, an explicit evaluation of the accuracy level of the estimated delay was conducted. Trajectory data for thousands of vehicles on six freeway facilities across the United States were analyzed, and a floating car's travel time and delay were generated (simulated) as the average travel time and delay of all its neighboring vehicles within a specified duration. This was found to be an inaccurate method. Although performance is influenced by the combination of such factors as the user-specified free flow speed (delay definition), the floating car intervals, the floating car generation method, and facility-specific traffic conditions, the assumed bottleneck capacity is observed to be the primary contributor to inaccuracy. Until a practicable method is found for determining the true flow between any two consecutive floating cars to supersede the assumed capacity, the estimation should be interpreted only in its comparative sense, such as tracing the trend of delay development for a freeway facility.
Comparison of Portable Speed Measurement Devices
Authors: Gates Tim J. , Schrock Steven D. , Bonneson James A.
Published: April 2007

The accuracy and precision of five common portable speed measurement systems were evaluated in a controlled field evaluation. The following systems were evaluated: traffic classifier with pneumatic tubes, traffic classifier with piezoelectric sensors, tape switches, radar, and lidar (i.e., police laser). A test vehicle with a calibrated Nitestar distancemeasuring instrument (DMI) made 100 passes through the test site at two speed levels (50 passes at 55 mph, 50 passes at 35 mph), and speed was recorded by each device for each pass. DMI speed was deemed the "true" speed for each pass, and deviations from the DMI speed for a given device were considered errors. Paired t-tests were performed on the speed data measured by each device versus the DMI. The following conclusions were drawn: ( a) All devices performed equally well for the 35-mph trials. ( b) Lidar and radar were the most accurate and precise devices for the 55-mph trials. ( c) For all devices, any errors that occurred for a single speed measurement were relatively small (less than ±1.5 mph). ( d) With the exception of radar, all devices were slightly less accurate and less precise at higher speeds. ( e) There was little difference in performance between on-pavement devices (i.e., tubes, piezoelectric sensors, and tape switches). ( f) Inaccuracies observed in on-pavement equipment likely were caused by slight measurement errors during placement of the sensors or movement of the sensors resulting from repeated tire hits. Because all devices were relatively accurate, the researchers recommended that portable speed measurement equipment be selected to suit the characteristics of a given data collection situation.
Economic Foundations of Ohio River Navigation Investment Model
Authors: Curlee T. Randall , Busch Ingrid K. , Hilliard Michael R. , Oladosu Gbadebo , Southworth Frank , Vogt David P.
Published: April 2007

The Ohio River Navigation Investment Model (ORNIM) estimates the benefits of navigation improvements and balances those estimated benefits against the estimated costs of improvements. The economic assumptions within ORNIM are identified; the rationale for these assumptions is provided; and how these assumptions alter the estimates of inlandwater navigation benefits, as compared with those of the theoretical model, are addressed. ORNIM is a spatially detailed partial equilibrium model that incorporates the following assumptions: ( a) demand for individual movements, provided exogenously, is perfectly inelastic; ( b) willingness to pay (WTP) for individual river movements is equal to the exogenously given least-cost alternative rail rate; and ( c) the supply of rail for individual movements is perfectly elastic at the exogenously given rail rate. The first assumption biases upward estimates of with-project benefits. However, empirical evidence on demand elasticity and WTP suggests that these assumptions are reasonable in the short run. In the long run, decisions to move cargo by water depend only in part on river rates, with environmental and energy policies also being critical. The demand for waterway movements is determined exogenously to ORNIM, and the Corps' recent scenario-based approach to demand projection is laudable. The third assumption unequivocally biases downward ORNIM's estimate of with-project benefits. Future ORNIM enhancements include improvements in analyzing congestion fees, environmental externalities, traffic management, and system reliability as well as improvements in data quantity and quality. ORNIM, like other navigation models, is data constrained. Without significant data improvements, attempts to relax economic assumptions within ORNIM are of questionable value.
Role of Technology in Achieving Environmental Policy Goals in the Maritime Transportation System
Authors: Theis Melissa , Cass Nicole D. , Corbett James J. , Byrne John
Published: April 2007

The maritime transportation system (MTS), a truly multimodal industry, is in the unique position of being able to implement technologies borrowed from other areas and combine them with innovations developed within the industry to achieve continued advancement. There is an increasing need for better environmental performance in the industry; this is generally accomplished through new or adopted technologies. Previous research has explored the independent ideas of individual technological or environmental policy achievements. The role of technology in achieving environmental policy goals in the marine shipping industry is addressed, and the efficacy of various types of environmental policy mechanisms in promoting appropriate technologies is considered. Two case studies involving the environmental impacts associated with MTS (air pollution and nonindigenous species introductions) are evaluated. These two environmental problems were initially regulated with environmental standards but have shown a potential for being addressed with more innovative policy approaches. A better understanding of how the industry creates and diffuses technologies and the manner in which various policy mechanisms promote these activities could lead to more effective long-term solutions for environmental improvements.
Comparison of Numerical Schemes for Macroscopic Traffic Flow Models
Authors: Ngoduy D. , Hoogendoorn S. P. , Van Zuylen Henk J.
Published: April 2007

Accurate and reliable numerical algorithms for the solution of macroscopic traffic flow models are very important to ensure that the models' properties are accurately represented. An inappropriate numerical scheme may result in deviate or erratic model behavior, such as large numerical dissipations and numerical instabilities. A new computation scheme for the numerical approximation of solutions of Payne-type models is presented. This scheme is proved to satisfy the positive constraints of traffic variables and thus prevents traffic from moving upstream. In addition, an automated model calibration approach is proposed; it is applied to determine the parameters of the considered macroscopic model for different numerical schemes (Steger-Warming, MacCormack, and the proposed numerical scheme). Predictions from the various numerical approximation models are compared with observations from the validation data set. On the basis of this comparison, it is concluded that the proposed numerical scheme is both more accurate and more robust than the other schemes considered. It yields a small mean squared error and fast computation due to the ability to use a larger time-step; it also provides accurate results in regions in which the gradients of the speeds and densities are high.