bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Laboratory Wheel-Tracking Test Results with Wes Track Performance
Authors: Williams R. Christopher , Prowell Brian D.
Published: April 2007

In 1990, members of FHWA participated with other industry and highway agencies in a European asphalt study tour to examine pavement technology. One of the technologies brought back from this tour was laboratory wheel-tracking devices. However, the ability of these devices to predict or rank field performance has been questioned. WesTrack provides a unique opportunity for comparing accelerated laboratory wheeltracking devices with full-scale pavement performance under controlled conditions. The three devices examined here are the asphalt pavement analyzer (APA), the French pavement rutting tester (FPRT), and the Hamburg wheel-tracking device (HWTD). WesTrack is a 2.9-km oval test track with each tangent consisting of 13- to 70-m sections. Samples for laboratory evaluation using three wheel-tracking devices were taken from the 5-m sampling segments of the rehabilitated sections: 10 sections placed in the summer of 1997. Based on the data and analyses in this study, the three laboratory devices examined satisfactorily correlate with the permanent deformation of the WesTrack sections studied. The correlations are 89.9, 83.4, and 90.4 percent for the APA, FPRT, and HWTD, respectively. The devices, although not perfect in predicting or ranking section performance, did exhibit increased variability with poorer performance. This increased variability with mean permanent deformation or creep rate allows for a rational method to establish mixture design specifications for all three devices. The procedure exhibited here is flexible, allowing an agency to select the level of performance desired. The selection of an appropriate test temperature that reflects the in-service temperature at which the pavement will be expected to perform was found to be necessary as well.
Municipal Implementation of Superpave Technology
Authors: Brooks Don , Hein David , Uzarowski Ludomir , Emery John
Published: April 2007

The reconstruction of 30 km of County Road 2 by the county of Frontenac in 1996 provided the opportunity for municipal implementation of Superpave performance graded asphalt binder and volumetric mix design technology. The Superpave surface course asphalt mix was placed over a cold in-place recycled binder course pavement. Placement and compaction procedures were similar to those for conventional asphalt mixes, with the application of a light soap solution to avoid pickup associated with the polymer-modified performance graded asphalt cement on compaction equipment. The Superpave mix properties for trial batches were verified with a Superpave gyratory compactor. Basic mechanistic properties (resilient modulus, resistance to permanent deformation, and resistance to fatigue) of the Superpave surface course mix were determined with the Nottingham asphalt tester. Three long-term performance monitoring test sections were established at representative locations on County Road 2. The test section performance monitoring included visual distress surveys, structural capacity testing with the falling weight deflectometer, and transverse profiles with the digital incremental profiler (Dipstick). Monitoring of the County Road 2 Superpave pavement indicates that, after almost 3 years of service, the pavement has no significant surface distresses and is in excellent overall condition.
Understanding Asphalt Mastic Behavior Through Micromechanics
Authors: Buttlar William G. , Bozkurt Diyar , Al-Khateeb Ghazi G. , Waldhoff Angela S.
Published: April 2007

The mechanical properties of asphalt-mineral filler mastics have long been known to significantly influence the overall performance of paving mixtures. However, reinforcement mechanisms associated with the presence of fillers in asphalt mastics are not well understood. Particulate composite micromechanical models are shown to be a powerful tool for separating various reinforcing mechanisms in asphalt mastics, including volume filling, physiochemical, and particle-interaction reinforcement. The generalized self-consistent scheme model is shown to predict very reasonable baseline reinforcement levels for asphalt mastics, and simplified prediction tools are presented as an alternative to the cumbersome micromechanical solution. An experimental program was conducted to evaluate micromechanical predictions of mastic properties over a broad range of temperatures and filler concentrations. A new equivalent rigid layer modeling technique was developed, which suggests that stiffening effects observed in mastics beyond those due to volume filling may be largely explained by an effective increase in volume concentration of rigid inclusions due to a rigidly adsorbed asphalt layer just 0.02 to 0.10 μm thick. Particle-interaction reinforcement appears to play a smaller role, possibly as a result of the interaction of partially altered asphalt layers, and was observed to be significant only at very high filler contents. More work is needed to better understand the nature of physiochemical reinforcing and to study other possible stiffening mechanisms in mastics such as agglomeration, state of dispersion, and particle-size distribution.
Quantifying Laboratory Compaction Effects on the Internal Structure of Asphalt Concrete
Authors: Masad Eyad , Muhunthan B. , Shashidhar Naga , Harman Thomas
Published: April 2007

The performance of asphalt concrete (AC) mixtures is influenced by its internal structure, which refers to the arrangement of aggregates and their associated air voids. Currently, most of the discussion on the effects of internal structure on AC performance is qualitative. This study proposes computer-automated image analysis procedures to quantify the internal structure of AC. Internal structure is quantified in terms of aggregate orientation, aggregate contacts, and air void distribution. The new procedures are useful tools to describe and compare AC materials produced by different compaction methods and mix designs. The new procedures are used to study the difference in internal structure of AC specimens compacted with the Superpave gyratory compactor (SGC) and the linear kneading compactor (LKC). Specimens compacted with the SGC were found to have aggregates with more preferred orientation and fewer contacts than specimens compacted with the LKC. In addition, SGC specimens were found to have more air voids at the top and bottom, whereas air voids in LKC specimens were found to increase from the top to the bottom.
Analysis of Transportation Management Strategies for 2020 Regional Transportation Plan
Authors: Zavattero David A. , Ward Janice A. , Rice Daniel F.
Published: April 2007

The 2020 Regional Transportation Plan (RTP) is the first long-range plan that not only identifies transportation management strategies but also analyzes alternative levels of strategy implementation. The development of the transportation management component was coordinated through the Transportation Control Measures Development Task Force. Transportation management project proposals were analyzed with the regional travel model and off-network methods as part of the scenario testing for the plan. The results indicated that a regional strategy to establish a comprehensive and coordinated transportation management program can significantly increase transit ridership, reduce automobile use, increase ridesharing, lower regional vehicle miles of travel (VMT), and reduce emissions as compared with conditions without these management strategies. A range of transportation management strategies was identified for inclusion in the RTP. Selection of 11 specific strategies was based on their applicability by the year 2020 and their contributions to achieving RTP goals and objectives. Transportation demand management, transportation system management, and intelligent transportation system applications were analyzed to quantify their effectiveness and to finalize the package of strategies for inclusion in the RTP. Trip making, VMT, and emission reductions were calculated for each of the 11 strategies to compare the impact with the cost of implementation. An overview of the strategy objectives and the methods used to calculate the performance impacts of each strategy is provided. Costs associated with different levels of implementation were estimated and project requirements identified. The final package of 11 transportation management strategies, implementation efforts, funding requirements, and the expected benefits of these strategies are also discussed. The 11 strategies resulting from this planning process make up the transportation management component of the 2020 RTP.
PLAN⋄HOV: Case-Based Reasoning Planning Tool for High-Occupancy Vehicle Lane Analysis in a Geographic Information System Environment
Authors: Khattak Asad J. , Renski Henry
Published: April 2007

Historical cases can be used to inform new planning and policy situations. Existing knowledge about high-occupancy vehicle (HOV) lane cases can provide quantitative and qualitative information to support decisions about proposed HOV lanes. Using case-based reasoning (CBR) to formalize the use of historical cases, a computer program called PLAN⋄HOV is demonstrated. CBR complements formal modeling by systematically presenting knowledge to users in situations in which formal models are under development or qualitative information is important. PLAN⋄HOV is a planning tool developed in a geographic information system environment that allows users to understand the potential impacts of proposed HOV lanes on the basis of experiences with similar HOV lanes. All historical HOV lane cases represented in PLAN⋄HOV have HOV lane attributes, associated impacts, and the implementation context. In addition, historical cases contain information about lessons learned, such as inferences about their success or failure, prescriptions, and case quality. The historical cases can be accessed by matching them with the dimensions of the current context (e.g., population and network structure) and the proposed HOV lane actions, such as adding a 2+-person HOV lane that operates during peak periods. The retrieval and display of historical cases can occur with varying levels of matching stringency. Users can examine the matched case(s) for their qualitative content (such as controversies over HOV lanes) and also use them to anticipate the impacts of the proposed lane (e.g., mode shift caused by HOV lanes). The development and use of this case-based planning tool are described.
Predicting Change in Average Vehicle Ridership on the Basis of Employer Trip Reduction Plans
Authors: Winters Philip L. , Cleland Francis A. , Pietrzyk Michael C. , Burris Mark W. , Perez Rafael
Published: April 2007

Artificial neural network (ANN) models are described, and efforts to build a model to predict changes in average vehicle ridership using about 7,000 employer trip reduction plans from three cities are highlighted. The development of the application is summarized; the neural network model performance is compared with other analytical approaches; and the results of the field test are summarized. Researchers at the Center for Urban Transportation Research combined the three data sets, identified model inputs and outputs from the data, and built the neural network model. This step also included building alternative models using regression and discriminant analysis to measure relative ANN performance. These models were compared with the FHWA’s transportation demand management model. The ANN model built only with data from Los Angeles was validated using a separate data set and evaluated according to the model’s ability to classify the change in average vehicle ridership (AVR) within an acceptable range. The final step was the validation of the model using data from other sites. The result was a model and software built on data from Los Angeles and Tucson that performed well when tested with data from Phoenix. On the basis of this project, the ANN model predicted an acceptable range of changes in AVR and was proven to be transferable to another city. Furthermore, the ANN model outperformed other analysis tools and was easier to use. Finally, the model provides a basis for helping to assess the impacts of employer trip reduction programs with minimal data collection requirements.
Evaluation of Mobile Surveillance and Wireless Communication Systems Field Operational Test
Authors: Mastako Kimberley Allyn , Klein Lawrence A.
Published: April 2007

From June 1994 through September 1998, the California Department of Transportation and FHWA conducted a field operational test (FOT) to evaluate the benefits a mobile surveillance and wireless communication system provides in support of freeway surveillance, ramp metering, and arterial traffic management. Six surveillance and three ramp meter trailers were designed and built for deployment in areas where permanent detectors, electrical power, and landline communications are not available. A retransmission or relay site and data reception equipment for use at traffic management centers and research facilities also were installed. The major components of the surveillance and wireless communication system are black-and-white cameras that supply imagery and data to video image processors; color pan, tilt, and zoom surveillance cameras; narrow and wideband spread spectrum radios; 170 controllers; video compressors; and a trailer-based power distribution system. An independent evaluation of the FOT was conducted in accordance with FHWA guidelines. The FOT showed that the trailers could be effective aids to traffic management when site survey and selection guidelines developed during the FOT are followed and trailer maintenance is performed. At the trailer locations used in the tests, the measured traffic flow parameters and compressed video imagery were able to provide local-responsive ramp metering onto a freeway main line during periods of heavy traffic and video imagery that facilitated control of arterial traffic signals. Data were effectively shared among state and city traffic management centers and university research facilities over spread spectrum radio links.
Effectiveness of Wireless Phones in Incident Detection: Probabilistic Analysis
Authors: Tavana Hossein , Mahmassani Hani S. , Haas Carl C.
Published: April 2007

Deployment of intelligent transportation systems (ITS) in major cities of the United States and inauguration or upgrading of transportation management centers (TMCs) have enhanced the ability to better manage transportation networks. One of the main goals in design and operation of TMCs is the ability to detect incidents promptly and reliably. Several methods are implemented to achieve this goal, including methods relying on data collected by loop detectors or other technologies. Recent limited experiments suggest that wireless telephones can be an effective tool in incident detection. A probabilistic analysis approach is adopted here to analytically determine the effectiveness of this method for incident detection. This analysis indicates that wireless phone calls to emergency services (i.e., 911) can provide valuable and timely information for incident detection. Furthermore, adoption of the Federal Communications Commission (FCC) requirements for identifying and locating E911 callers would reduce the likelihood of receiving false alarms from wireless phone callers; hence, it would provide TMCs with an inexpensive, fast, and reliable source of information for incident detection and verification.
Pitfall To Avoid When Estimating Incident-Induced Delay by Using Deterministic Queuing Models
Authors: Olmstead Todd
Published: April 2007

The deterministic queuing model is the most widely used method to estimate the delay caused by freeway incidents. It has been applied in numerous studies to determine the impacts of incidents and to estimate the benefits of policies designed to reduce such impacts. Typically, the average duration per incident type is used to estimate the incident delay. This approach assumes that the “delay due to an average incident” is the same as the “average delay due to incidents.” In fact, because delay is a convex function of incident duration, the “delay due to an average incident” is always smaller than the “average delay due to incidents.” This paper shows that the underestimate of the total delay is a function of ( a) the variance of the incident duration times, ( b) the severity of the type of incident under consideration, and ( c) the number of incidents of the type under consideration. A formula is presented that accurately determines the total delay. The formula depends on the mean and the variance of the incident duration times but does not require knowledge of the individual duration times. It is then shown how the averaging of duration times should be carried out in practice to avoid under- or overestimating the benefit of a reduction in incident duration. The concepts are illustrated using a stylized numerical example based on incident data from the Emergency Traffic Patrol in Chicago.
Using Dual Loop Speed Traps To Identify Detector Errors
Authors: Coifman Benjamin
Published: April 2007

Dual loop speed traps have a distinct advantage over single loop detectors because the speed trap detection system is redundant. Each vehicle is observed twice under normal operating conditions, once at each loop. The two observations are normally used to measure velocity, but as this paper demonstrates, the redundancy can also be used to assess the performance of the speed trap and identify detector errors. At free-flow velocities, the time each detector is occupied by a vehicle (i.e., the ontime) should be virtually identical, regardless of the vehicle length. Many hardware errors will cause the two on-times to differ. Exploiting this property, a formal methodology for testing speed traps off-line has been developed, and ways to extend the work to on-line testing are suggested. The work is used to evaluate several loop sensor units, revealing problems in two models. A second example shows how the work can be used to detect cross talk between sensor units.
Local and Iterative Searches for Combined Signal Control and Assignment Problem: Implementation and Numerical Examples
Authors: Lee Chungwon , Machemehl Randy B.
Published: April 2007

Traffic signal-setting policies and traffic assignment procedures are mutually dependent. The combined signal control and traffic assignment problem deals with this interaction. With the total travel time minimization objective, gradient-based local search methods are implemented. Deterministic user equilibrium is the selected user route choice rule, Webster’s delay curve is the link performance function, and green-time-per-cycle ratios are decision variables. Three solution codes are implemented, resulting in six variations including intersections with multiphase operation and overlapping traffic movements. For reference, the iterative approach is also coded, and all codes are tested in four example networks at five demand levels. The results show the numerical gradient estimation procedure performs best, although the simplified local searches reduce the large network computational burden. Demand level as well as network size affects the relative performance of the local and iterative approaches. As demand level becomes higher, ( a) in the small network, the local search tends to outperform the iterative search, and ( b) in the large network, the opposite result is obtained.
Estimating Queue Lengths by Using SIGNAL94, SYNCHRO3, TRANSYT-7F, PASSER II-90, and CORSIM
Authors: Mystkowski Cindy , Khan Sarosh
Published: April 2007

A variety of programs are available to aid transportation engineers in their evaluation of signalized intersection operations. One measure of effectiveness—queue length—is examined. The methods used to estimate queue length, which often are not readily available, are documented for five programs; the definition used by each is clarified; and the queue length estimate of each program is compared with field data from six intersections in Denver, Colorado. Of the programs studied, three produced reasonable results 70 to 85 percent of the time—CORSIM, TRANSYT-7F, and SIGNAL94. PASSER II-90 results are reasonable 50 percent of the time. SYNCHRO3 produces reasonable results 50 percent or 85 percent of the time, depending on the queue estimation desired. The queue length estimates for high, medium, and low volume-to-capacity ratio conditions, for all programs, are also documented.
Signal Timing Optimization for Oversaturated Networks Using TRANSYT-7F
Authors: Li Min-Tang , Gan Albert C.
Published: April 2007

Oversaturated traffic networks with spill-back conditions are becoming more common, and their signal timing is difficult to optimize. Up through release 7, TRANSYT-7F, a signal timing tool for traffic network simulation and optimization, was designed for modeling only undersaturated networks. Release 8, which was recently completed, has the added capability to model oversaturated networks. Because signal timing optimization for oversaturated networks requires emphasis on traffic throughput and queue management rather than on traditional delay and progression, four new optimization objective functions were introduced in release 8. This paper introduces these new objective functions and compares their ability to produce optimal timing plans with the abilities of the four traditional objective functions. The types of spill-back effects explicitly modeled by release 8 are also introduced. For performance evaluation, a data set involving two closely spaced ramp terminals at an urban diamond interchange was modeled. The CORSIM microscopic simulation program was used as a tool to evaluate optimal timing designs produced by different objective functions. The results indicate that the new objective functions were able to produce superior timing plans that yield lower average vehicle delay and reduce spill-back conditions.
Traffic Signal Optimization Program for Oversaturated Conditions: Genetic Algorithm Approach
Authors: Park Byungkyu , Messer Carroll J. , Urbanik Thomas
Published: April 2007

Traffic signal optimization programs have been used widely among transportation professionals. However, none of the existing computer programs can optimize all four traffic control parameters (i.e., cycle length, green split, offset, and phase sequence) simultaneously, even for undersaturated conditions. In this paper, a genetic algorithm-based signal optimization program that can handle oversaturated signalized intersections is presented. The program consists of a genetic algorithm (GA) optimizer and a mesoscopic traffic simulator. The GA optimizer is designed to search for a near-optimal traffic signal timing plan on the basis of a fitness value obtained from the mesoscopic simulator. The proposed program is compared with the newly released TRANSYT-7F version 8.1 on the basis of CORSIM simulation program. Three different demand volume levels—low, medium, and high demand—are tested. For the low-demand and high-demand volume cases, the GA-based program produced statistically better signal timing plans than did TRANSYT-7F in terms of queue time. In the case of medium-demand volume level, the signal timing plan obtained from the GA-based program produced statistically equivalent queue time compared with TRANSYT-7F. Both programs are judged to provide superior capability for oversaturated conditions due to their queue blockage model when compared with previously available signal timing optimization software.
Characterizing Seasonal Variations in Flexible Pavement Material Properties
Authors: Ovik Jill , Birgisson Bjorn , Newcomb David E.
Published: April 2007

As agencies progress toward mechanistic-empirical flexible design procedures, it is critical to quantify the relationships between climate factors and the resulting seasonal variations in pavement layer moduli for a given region. This was investigated for flexible pavement structures and climate conditions specific to Minnesota. The objective of this study was to quantify the relationships between climate factors, subsurface conditions, and pavement material properties for use in a mechanistic-empirical design procedure that reflect conditions specific to Minnesota. The approach used to establish these relationships may suggest possible directions for similar studies in other regions. The data used in this study were obtained from the Minnesota Road Research Project, located on Interstate 94 in central Minnesota. The extensive instrumentation, on-site weather station, and deflection testing performed at this facility provide valuable environmental and pavement response data. The results show that the maximum stiffness for the pavement layers occurs in the winter, and the minimum stiffness occurs at different periods in a typical year for the different layers. The asphalt concrete modulus is at a minimum in the summer when temperatures are high. The base layer modulus is at a minimum in the spring thaw period, and the subgrade layer modulus is at a minimum in the late spring and summer months. The seasonal variations in pavement layer moduli are used to establish seasonal factors for each layer which describe the modulus cycling in a typical year. These factors may be applied to a mechanistic-empirical design procedure specific to Minnesota.
Considerations for High-Performance Concrete Paving: Recommendations from 20 Years of Field Experience in Texas
Authors: McCullough B. Frank , Dossey Terry
Published: April 2007

Presented are recommendations for high-performance concrete paving (HPCP) practice drawn from 20 years of design and monitoring of the performance of continuously reinforced concrete (CRC) pavements in Texas. Performance indicators used were crack spacing distribution, crack width, crack randomness, delamination spalling, and vertical distribution of tensile strength. Variables studied were aggregate type, aggregate blending, placement season, placement time of day, placement above 32°C (90°F), use of crack initiators, use of skewed transverse steel, evaporation rate, percent steel reinforcement, and steel bar diameter. The variables studied are ranked in the order they affected performance, to identify which are significant and can be controlled in the design and construction phases. The focus is on the most recent experimental pavements designed and built specifically to study HPCP in Texas—85 CRC test sections built at eight locations between 1986 and 1995 in the greater Houston area. Each project consisted of 8 to 22 experimental sections of slightly different design. These sections were closely controlled and monitored during construction, and periodic condition surveys continue to be conducted. The recommendations offered are especially useful under adverse conditions, such as hot weather placement of portland cement concrete using high thermal coefficient aggregates, or paving during periods of high surface evaporation. Critical temperatures and evaporation rates are specified; using weather stations, maturity meters, or other devices that indicate in situ temperatures and evaporation rates, dangerous conditions may be identified in time to take corrective measures and thus ensure adequate performance.
Effect of Static and Fatigue Cracking on Concrete Strain Measurements
Authors: Roesler Jeffery R. , Barenberg Ernest J.
Published: April 2007

Three concrete specimen types were tested to failure under static and cyclic loading. Simply supported beams, fully supported beams, and fully supported slabs were constructed from the same concrete mix. Strain gauges were used to help determine the effect static and fatigue cracks had on concrete strain measurements. Static load tests for all specimen types found strain gauges overestimated bending stresses after 70 percent of the static strength of the concrete. Stresses based on cyclic strain measurements were not useful in predicting the bending stresses in the concrete specimens. The strain gauges accumulated permanent deformations almost immediately after cyclic testing started. For all specimen types tested, strain gauges indicated that cracking in concrete occurred in a localized narrow band. Concrete in the cracking plane had increased strain levels, whereas adjacent uncracked regions experienced a reduction in strain levels. Location of the failure crack on each specimen type was essential for interpretation of the strain data. Strain gauges allowed for the determination of the direction of crack propagation in slabs. Cracks began at the bottom edge of the slab and propagated across the bottom of the slab’s centerline. Vertical crack propagation through the slab’s depth occurred for the majority of the slab’s fatigue life. Strain measurements showed concrete slabs’ ability to resist load in directions perpendicular to the maximum stress not seen in fully supported beams and simply supported beams.
Experimental Verification of Rigid Pavement Joint Load Transfer Modeling with EverFE
Authors: Davids William G. , Mahoney Joe P.
Published: April 2007

The joint load transfer modeling capabilities of EverFE, a recently developed rigid pavement three-dimensional finite element analysis tool, are verified through comparisons with available experimental data. Dowel joint load transfer is examined via comparison of displacements predicted by EverFE with results from laboratory tests of two small-scale doweled pavement systems, and dowel looseness is shown to be a probable cause for experimentally observed differential joint displacements. Results of finite element analyses using EverFE’s nonlinear, two-phase aggregate interlock constitutive model are shown to agree well with available experimental data. A parametric study is performed that examines the effect of joint opening on aggregate inter-lock load transfer and illustrates the importance of considering nonlinearities in joint load transfer when predicting pavement response. Recommendations for future research on joint load transfer modeling are also discussed.
Study of a Method for Analyzing the Mechanical Behavior of Composite Pavement
Authors: Nishizawa Tatsuo , Fukute Tsutomu , Kokubun Syuichi
Published: April 2007

Presented is a structural model for predicting the mechanical behavior of composite pavements based on Ioannides and Khazanovich’s idea. In this model, a composite pavement is modeled by overlaid plate finite element method elements connected with a link element resting on a Winkler foundation. This concept is extended to the bonded interface condition between two layers by modifying the stiffness matrix of the plate element. The model was verified by comparisons of computed results with the measured results. The comparison revealed that the developed model can predict the bending strains in thin concrete overlay on asphalt pavement. Furthermore, curling deformations with the layer separation were examined to investigate the applicability of the model. It was found that the separation between the layers occurs if the bond strength at the interface is very low.
Artificial Neural Networks for Analyzing Concrete Airfield Pavements Serving the Boeing B-777 Aircraft
Authors: Ceylan Halil , Tutumluer Erol , Barenberg Ernest J.
Published: April 2007

An artificial neural network (ANN) model has been trained with the results of the ILLI-SLAB finite element program and has been used to predict stresses and deflections in jointed concrete airfield pavements serving the Boeing B-777 aircraft. The trained ANN model produces stresses and deflections with average errors of less than 0.5 percent of those obtained directly from the finite element analyses. Use of the ANN model has been found to be very effective for correctly predicting ILLI-SLAB stresses and deflections, in less than 1 s, with no requirements of complicated finite element inputs. On the other hand, elastic layered programs (ELPs) currently are being used in mechanistic-based pavement design procedures for the analysis of jointed concrete pavements. Corrections are required to such ELP solutions to account for the effects of finite slab size, load location on the slab, and load transfer efficiencies of the joints. This can be accomplished by using the ANN model, which is being expanded to handle all possible aircraft gear configurations with multiple-wheel loading conditions by the use of the superposition principle. As demonstrated for the solution of the B-777 aircraft gear loadings, trained neural network models eventually will enable pavement engineers to easily incorporate current sophisticated state-of-the-art technology into routine practical design.
Resistance of Steep Concrete Block Pavements to High-Velocity Water Flow
Authors: Ishai Ilan , Dalin Joseph S. , Rubin Hillel , Finkelstein Alexander
Published: April 2007

In some locations, the use of concrete block pavement (CBP) involves the combination of a very steep and storm-sensitive region with the consequent risk of high-velocity water flow on pavements. Under these conditions, and because of the special characteristics of CBP and its unknown response to high-velocity water flow, two problems must be addressed: ( a) the danger of sand erosion from the bedding layer and the joints between the blocks, because of surface drainage and water flow, and ( b) the danger of development of uplift forces from the downward water seepage. The cumulative effect of these two dangers may cause a gradual loss of support of the CBP, leading to total failure. CBP was tested under high-velocity water flow on a one-to-one scale, with definition of flow and failure mechanisms in the CBP and with the adoption of proper solutions. Five tests were performed in an experimental water flume, differing in type of bedding. Use of conventional sand bedding under continuous water-flow conditions was found to be inappropriate. Such bedding cannot provide the necessary stability for the CBP. However, the use of fine aggregate as bedding material ensured the stability of the CBP under continuous supercritical flow velocities and steep channel slopes. Excellent performance of the CBP was observed with the underlying fine aggregate bedding. The use of sufficiently coarse aggregate as bedding material is the proper engineering solution for preventing erosion and ensuring the absolute stability of a CBP under high water-flow velocities under supercritical conditions.
Hot-Mix Asphalt Overlay Design Concepts for Rubblized Portland Cement Concrete Pavements
Authors: Thompson Marshall R.
Published: April 2007

The Illinois Department of Transportation’s (IDOT’s) first interstate rubblization project was constructed in 1990 on I-57 near Pesotum as part of a rehabilitation study. Hot-mix asphalt overlays (HMA OL) were constructed over a rubblized jointed reinforced concrete pavement (JRCP) with a granular subbase. Excellent performance was achieved on the project, which had accommodated 7.5 million equivalent single-axle loads through 1998. Periodically collected falling weight deflectometer (FWD) data indicate the sections have retained their structural capacity and integrity. HMA fatigue distress has not developed. The success of the project prompted IDOT to consider portland cement concrete pavement (PCCP) rubblization and HMA OL a viable and cost-effective rehabilitation option. Rubblization is particularly appropriate for eliminating reflective cracking and for use when PCCP patching quantities are high or concrete deterioration is in an advanced stage. HMA OL fatigue considerations control the HMA OL thickness requirement for rubblized PCCPs. HMA OLs for rubblized PCCPs, generally in the 150-mm to 250-mm (6-in. to 10-in.) range, are thicker than those used in the traditional PCCP rehabilitation and HMA OL projects. IDOT uses mechanisticempirical (M-E) flexible pavement design procedures for full-depth asphalt and conventional flexible pavements. M-E–based HMA OL design procedures for rubblized PCCPs are being developed. In the M-E design procedures, the tensile strain at the bottom of the HMA layer is used to consider HMA fatigue. The structural behavior and HMA OL fatigue performance of the Pesotum sections are used in the initial development of the M-E–based HMA OL design procedures for rubblized PCCPs. Results from other rubblized PCCP projects are being used to refine and validate the M-E design concepts.
Rubblization of Concrete Pavements
Authors: Ksaibati Khaled , Miley William , Armaghani Jamshid
Published: April 2007

The Florida Department of Transportation is in the process of evaluating rubblizing concrete pavements as an effective rehabilitation technique for eliminating reflected cracks in asphalt overlays on top of concrete pavements. As part of that evaluation, a nationwide survey was performed to gather information about the practices of other departments of transportation with regard to rubblization and to determine the overall performance of rubblized sections in various states. The survey indicated that most states have a relatively small number of rubblized sections, with the exception of three states that have more than 10 sections each. The construction techniques, overlay thicknesses, and field performance varied from state to state. However, it was clear that most states are highly satisfied with rubblization as a good means for eliminating reflected cracks. Only a few states indicated problems with rubblization, mainly due to weak subgrade.
Experimental Cold In-Place Recycling with Hydrated Lime
Authors: Cross Stephen A.
Published: April 2007

The Kansas Department of Transportation (KDOT) uses cold in-place recycling (CIR) for approximately 120 to 160 km of pavement a year as a part of its 1-R maintenance program. Originally KDOT used asphalt emulsions as the additive in CIR mixtures, but on the basis of performance concerns it currently uses type C fly ash. Recent research indicates that the use of CIR with asphalt emulsion and hydrated lime, introduced as hot slurry, provides improved performance. KDOT constructed two test sections on US-283 using type C fly ash and cationic slow set (CSS-1) with hot lime slurry. Samples of the materials were obtained and laboratory evaluations undertaken to evaluate the performance of CIR with hot lime slurry. Two additional mixing grade asphalt emulsions, cationic medium set (CMS-1) and high float (HFE-150), were evaluated as well. Laboratory samples were tested for tensile strength, moisture sensitivity, and resilient modulus. Laboratory compacted samples were tested for rutting resistance and moisture damage by using the asphalt pavement analyzer (Georgia rut tester). Results indicate that the use of hot lime slurry resulted in an improvement in material properties that affect the performance of CIR pavements, regardless of the emulsion used, and that CIR with hot lime slurry could be an alternative to the use of type C fly ash.
Ten-Year Performance Review of In Situ Hot-Mix Recycling in Ontario
Authors: Kazmierowski Tom , Marks Pamela , Lee Stephen
Published: April 2007

In today’s climate of environmental and economic constraints coupled with a diminishing aggregate supply, in situ hot-mix recycling provides an important alternative to conventional pavement rehabilitation. In situ hot-mix recycling, including hot in-place recycling (HIR) and cold inplace recycling (CIR), is proving to be an economical rehabilitation technique that conserves granular materials and energy and results in zero waste. The Ministry of Transportation and the Regional Municipality of Ottawa–Carleton have rehabilitated in excess of 80 projects using in situ hot-mix recycling techniques since 1987. The HIR process is suitable for roadways exhibiting a variety of surficial nonstructural distresses. The HIR process involves heating the existing pavement surface, scarifying, adding rejuvenator, fine aggregates, or beneficiating hot-mix (admixture) as required, mixing, reprofiling, and compacting this hot mixture in a continuous operation. CIR is suitable for roadways with moderate to severe distresses where reflection cracking is a concern. CIR involves milling the existing pavement, screening for oversize, addition of asphalt emulsion, and mixing; then this cold renewed material is spread, reprofiled, and compacted on the roadway in one continuous operation. An overview on the design, construction procedures, test results, and pavement performance to date of in situ recycling is presented. Ten years of performance monitoring of the in situ recycling projects has resulted in the evolution of design strategies and performance specifications. Their effectiveness, limitations, and future utility on highway contracts are discussed.
Relation of Field Cracking to Layer Stiffness of Cold In Situ Recycled Materials
Authors: McKeen R. Gordon
Published: April 2007

In 1996 the Alliance for Transportation Research Institute completed a comprehensive evaluation of 45 cold in situ recycling (CIR) pavement sections on New Mexico State Highway and Transportation Department routes built between 1984 and 1990. The results of further investigation into observed correlations between visual condition surveys, as an indicator of field performance, and the CIR stiffness measured on cores are reported. It was observed that CIR projects in New Mexico that are older than 9 years, with measured resilient modulus exceeding 6000 MPa and indirect tensile strength (ITS) exceeding 800 kPa, also exhibited reduced pavement condition index ratings based solely on environmental cracking distress. Reported is a direct comparison with some additional stiffness data and field performance for pavements recycled with different additives. Accelerated aging following Strategic Highway Research Program procedures was used to assess some samples tested. New sections evaluated were constructed by using hot lime slurry, cement, and a cement-fly ash blend. The criteria for cracking threshold observed in CIR materials appeared to be unaffected by addition of hot lime slurry and were quite different from those for layers recycled with cementious materials. It is proposed that criteria noted for resilient modulus and ITS may be used to guide the development of cold recycle laboratory mix design in combination with accelerated aging to simulate hardening under field conditions. By properly selecting the type of additive and the amount, more crack-resistant pavement sections may be constructed. Recommendations are developed for target values of stiffness in recycled materials.
Development of Performance Models Based on Department of Transportation Pavement Management System Data
Authors: Hand Adam J. , Sebaaly Peter E. , Epps Jon A.
Published: April 2007

The Nevada Department of Transportation (NDOT) is developing a network optimization system (NOS). The objective of the system is to evaluate various alternatives and to recommend the most cost-effective rehabilitation treatment to be used on the various sections of the state highway system. The NOS consists of several subsystems, including performance models, life-cycle cost analysis, and network optimization. Performance models have been developed for the rehabilitation treatments most commonly used by NDOT: overlay and mill/overlay. The performance models were developed on the basis of the pavement management system data that have been collected by NDOT for the last 15 years. The models were generated through statistical analyses that related the present serviceability index to age, traffic, environment, and structural and materials properties. First cost and annual maintenance cost figures were established to be used in the life-cycle cost analysis. The annual maintenance costs proved to be the most difficult figures to estimate due to the extremely large variability. After several attempts, the fixed period cumulative cost approach was identified as the best alternative to reducing the variability of the annual maintenance costs. In order to accomplish true network optimization, the entire NDOT highway system was subdivided into project segments (total number of segments is in excess of 800). Several databases were formed to house the data corresponding to each project segment. The NOS will use the performance models in conjunction with the supporting databases to conduct a fully automated optimization analysis.
Integrating Statewide Planning and Programming: A Principle-Based Approach
Authors: Zemotel Linda M. , Halvorson Randall K.
Published: April 2007

Initiatives that were begun at the Minnesota Department of Transportation (Mn/DOT) during the early to mid-1990s—decentralization of decision making, completion of a statewide transportation policy plan, and integration of performance measures into operations—have created conditions that make performance-based planning possible. Mn/DOT has adopted the philosophy of performance-based planning as the method to integrate planning and programming. Mn/DOT’s planning and programming process will be used to develop District Long-Range Plans and to produce the next update of the Statewide Transportation Plan. Performance measures and performance targets, which were developed for the outcomes of safety, quality of ride, condition of infrastructure, and basic levels of service, will be used to develop the district plans. Economic efficiency will be evaluated through the use of benefit-cost analysis for expansion projects. Values of Minnesota’s citizens will be considered through customer input. Two futures will be developed for the district plans. Future 1 will be constrained not by available funding but rather by the three investment principles of system performance, economic efficiency, and values of Minnesota’s citizens. Future 2 will be fiscally constrained and based on a 20-year financial forecast. It will be used to develop the State Transportation Improvement Program to link the planning process to the development of a program. Principle-Based Future 1 will be compared with Fiscally Constrained Future 2 to develop unmet needs. The difference will represent needs derived from a sound, analytical planning process. Results from the district plans will be incorporated into the next Statewide Transportation Plan.
Statewide Travel Forecasting Practice: A Critical Review
Authors: Horowitz Alan J. , Farmer David D.
Published: April 2007

Many states are now in the process of creating or upgrading their statewide travel forecasting methods. To assist those states, a review of existing forecasting practice was undertaken. This review consisted of interviews and documents from 45 states and of articles from the literature. Passenger models, freight models, and time-series models were reviewed. In addition, statewide models were compared to the many intercity models that were described in academic literature. Little consensus was found as to what should constitute a statewide model, and states varied greatly in their approaches. Those states with complete models tended to follow an urban modeling framework and used software originally designed for urban travel forecasting, in spite of the inherent differences in scales, planning needs, and data availability. Recommendations are made on how states can improve their forecasting methods and tailor them better to statewide planning requirements.
Toward Reflecting Public Perception of Quality of Service in Planning, Designing, and Operating Highway Facilities
Authors: Pfefer Ronald C.
Published: April 2007

Today’s highway administrators are operating in a more customer-conscious environment than in the past. Currently, however, expert judgments are used widely in lieu of road-user input. A comprehensive framework for studying and modeling public perceptions of quality of service (QOS) in a highway system is provided. The framework demonstrates how it is possible to observe the phenomena of drivers’ perceptions of QOS and to apply them in the context of highway planning. Some of the results from a pilot implementation of the concepts are presented for illustrative purposes. A multiyear research effort is proposed for developing tools that will allow decision makers to consider the perceptions of highway users in decision making.