bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Temperature Averaging on Predicted Pavement Life
Authors: Zuo Gang , Meier Roger W. , Drumm Eric C.
Published: April 2007

Mechanistic-empirical pavement design methods for flexible pavements are based on the assumption that the pavement life is inversely proportional to the magnitude of the traffic-induced pavement strains. These strains vary with the stiffness of the asphalt layer, which in turn varies with temperature. Because these relationships are nonlinear, the additional pavement life consumed at higher-than-average temperatures is not offset by savings at lower-than-average temperatures. As a result, whenever average pavement temperatures are used to determine the asphalt stiffness, pavement life is overestimated. Using hourly pavement temperature data from an instrumented pavement site in Tennessee, the effects of temperature averaging on predicted pavement life are examined and it is shown, for a typical full-depth asphalt pavement section supported by subgrade soils of different strengths, that pavement life can be overestimated by 50% to 75% if the temperatures are aggregated into monthly averages. It is also shown that even hourly average temperatures can produce errors if the hourly distribution of truck traffic is not taken into account.
Mechanistic Analysis of Top-Down Cracks in Asphalt Pavements
Authors: Svasdisant Tunwin , Schorsch Michael , Baladi Gilbert Y. , Pinyosunun Suwanna
Published: April 2007

Top-down cracks (TDCs) in flexible and rubblized pavements constitute a distress that has been reported in the United States and other countries. Researchers have reached different conclusions regarding the causes of TDCs. In this study, field and laboratory investigations were conducted on conventional flexible and rubblized pavements exhibiting TDCs. The engineering characteristics of the pavement layers were obtained from the analysis of field data and laboratory test results. Detailed mechanistic analyses were then conducted using these characteristics to determine the potential for TDCs. The results of such analyses were compared with field data and are presented and discussed in this paper. The results and field data show that ( a) surface radial tensile stress induced by wheel loads and enhanced by differential stiffness due to construction, temperature, and aging can cause TDCs, ( b) aging of the asphalt binder decreases the tensile strength and the tensile strain at failure of the asphalt mix, and ( c) the locations of the maximum surface tensile stress predicted by the mechanistic analysis correspond very well to the locations of the TDCs observed in the field.
Development and Performance of Interlayer Stress-Absorbing Composite in Asphalt Concrete Overlays
Authors: Dempsey B. J.
Published: April 2007

An interlayer stress-absorbing composite (ISAC) was developed and evaluated for the purpose of effectively alleviating or mitigating the problem of reflection cracking in an asphalt concrete (AC) overlay. ISAC materials and performance properties were carefully selected through comprehensive theoretical studies and laboratory evaluation programs. The ISAC system consists of a low-stiffness geotextile as the bottom layer, a viscoelastic membrane layer as the core, and a very high stiffness geotextile for the upper layer. In order to evaluate the effectiveness of the ISAC layer to control reflective cracking, a laboratory pavement section with an AC overlay placed on a jointed portland cement concrete slab was constructed and tested in an environmental chamber. A mechanical device was used to simulate thermal strain in the slab, and the joint was opened and closed at an extremely slow rate. The testing was conducted at −1.1°C, and strain in the overlay was monitored using a sensitive linear variable differential transducer device. The force required to pull and push the slab was monitored using a load cell placed between the slab and a hydraulic ram. Performance of ISAC was evaluated by comparing the cycles to failure of an ISAC-treated overlay with the performance of a control section without ISAC and of test sections containing two commercially available products. The base isolation properties of the ISAC system were demonstrated in the laboratory evaluation studies, which indicated that the ISAC system vastly outperformed the control section and the sections with the two commercial products tested. Several years of field performance testing have show that the ISAC system is highly effective for mitigating reflective cracking in AC overlays used on both airport and highway pavement systems.
Evaluation of Performance of Full-Depth Reclamation Mixes
Authors: Mallick Rajib B. , Bonner David S. , Bradbury Richard L. , Andrews Jamie O. , Kandhal Prithvi S. , Kearney Edward J.
Published: April 2007

The full-depth reclamation (FDR) process consists of reclaiming all of an asphalt-bound section along with a predetermined amount of underlying base, with some additive. The objectives of this study were to determine the suitable compactive effort for designing FDR mixes, evaluate the benefits of using different types of additives in terms of improvement of pavement life, and determine suitable structural numbers for pavements recycled with different types of additives. The scope of work for this part of the study consisted of conducting falling-weight deflectometer (FWD) tests, testing an existing pavement before FDR, sampling of materials during FDR, determining the density of in-place material after compaction, compacting of loose mix in the laboratory, determining the density of the compacted samples, conducting FWD testing on the finished pavement, determining the resilient modulus of in-place cores, and analyzing the data to determine the suitable number of gyrations, improvement in pavement life, and structural numbers. It was concluded that samples should be compacted to 50 gyrations during mix design and that a minimum of 98% of density of in-place loose mix samples, compacted to 50 gyrations, should be achieved in the field at the end of compaction. Cost comparison showed that for the options considered in this study, recycling with emulsion (3.4%) and lime (2%) is the most cost-effective option. A visual evaluation of recycled sections after one year showed no significant distress in any section except the one with water as additive, in which a moderate amount of edge cracking was noted.
Impact of Different Types of Modification on Low-Temperature Tensile Strength and Tcritical of Asphalt Binders
Authors: Man Sze Ho Susanna , Zanzotto Ludo , MacLeod Daryl
Published: April 2007

The introduction of the Superpave®asphalt binder specification provided the asphalt industry with a useful guideline for choosing appropriate materials to meet the requirements of a specific climate. Acid, alkaline, and polymer modification are just some of the ways to modify asphalt to meet the Superpave specification. The direct tension test (DTT) technique was applied to study the low-temperature properties of modified asphalt in terms of DTT failure stress values and the critical cracking temperature ( Tcritical). The bending beam rheometer (BBR) usually failed to detect improvement in low-temperature performance in polymer-modified asphalt (PMA). DTT results show that elastomeric polymer modification improves the low-temperature performance of PMA. In some PMAs, the failure stress value was higher than 9.5 MPa. The DTT technique for PMA was also reviewed. The effect of acid and alkaline modifiers on asphalt materials was studied. Acid or alkaline modification of asphalt was found to be only temporary and to be reversible. Acid modification of asphalt can be reversed by reaction with alkaline materials such as lime or antistripping agents. Alkaline modification of asphalt can be reversed by reaction with acidic materials such as carbon dioxide. Alkaline also can be washed away by water. Even though the BBR suggested a slight improvement in the low-temperature performance in acid- or alkalinemodified asphalt, the DTT failure stress values and Tcritical did not confirm this improvement. A relatively simple procedure that allows detection of acid or alkaline modification of asphalt materials is described.
Effect of Various Aging Techniques on Asphalt Low-Temperature Properties
Authors: Knorr Daniel B. , Davison Richard R. , Glover Charles J.
Published: April 2007

The effects of various aging techniques on asphalt low-temperature properties were investigated in three phases. In Phase I, it was shown that 38 days’ aging of a 1-mm-thick asphalt film at 60°C and 1 atmosphere of air is approximately equivalent to 20 h in the pressure-aging vessel (PAV) of a 3.2-mm-thick film at 100°C after both have been rolling thin-film oven test aged. Low-temperature properties of the samples were found not to vary significantly between the PAV and environmental room–aged material. In Phase II of this work, a correlation was developed from the high-temperature parameter G*/sin(δ) at 58°C and 10 radians/s to correct the low-temperature performance grade when it is desirable to skip the long-term aging procedure. In Phase III of this study, it was shown that as asphalts are aged for extended periods, their relative ranks with respect to Strategic Highway Research Program low-temperature specifications may change. Furthermore, as asphalts are aged for extended periods, the low-temperature grades move from being limited by stiffness at short aging times to being limited by m-value (creep rate) at longer aging times.
Effect of Hydrated Lime on Long-Term Oxidative Aging Characteristics of Asphalt
Authors: Huang Shin-Che , Claine Petersen J. , Robertson Raymond , Branthaver Jan F.
Published: April 2007

An experiment involving neat asphalts AAD-1, ABD, and their mixtures with two different grades of hydrated lime was conducted to investigate the effect of lime on the long-term aging characteristics of asphalt binders. Rheological properties of unaged and aged asphalt-lime mixtures were measured with a dynamic shear rheometer at 25°C (77°F) and 60°C (140°F). The addition of hydrated lime to one asphalt (AAD-1) effectively reduced oxidative age hardening. In addition, the phase angle reached the same value as aging time reached after approximately 800 h at 60°C in the pressure-aging vessel for AAD-1 and its mixtures with lime. After 800 h of aging, the phase angle was greater for the limetreated asphalt than for the untreated asphalt, and it continued to decrease at a slower rate. This result indicates that the addition of lime to this asphalt increases the initial stiffness of the binder, but, more importantly, it preserves elasticity during long-term oxidative aging. Thus, for this asphalt, at a level of oxidation typical of pavements, limetreated and untreated asphalts arrived at the same viscosity with time, but the lime-treated asphalt had better viscous flow properties than the untreated asphalt. It could then be predicted that the aged, lime-treated asphalt would be more resistant to fatigue cracking. The other asphalt tested (ABD) did not exhibit substantial effects of lime on the rate of oxidative age hardening. This highly compatible, low-asphaltene asphalt is not typical of most paving asphalts. Because hydrated lime has been shown to reduce oxidative age hardening both in the laboratory and during the first few years in the pavement, adding hydrated lime should extend the useful lifetime of most asphalt pavements.
Surface Energy Measurement of Asphalt and Its Application to Predicting Fatigue and Healing in Asphalt Mixtures
Authors: Cheng DingXin , Little Dallas N. , Lytton Robert L. , Holste James C.
Published: April 2007

Cohesive and adhesive bonding within the asphalt—aggregate system are directly related to the surface energy of the asphalt. The thermodynamic changes in the surface energy of adhesion and cohesion are related to the de-bonding of the interface between asphalt and aggregate and to cracks that may occur within the mastic, respectively. However, it is also true that thermodynamic changes in the surface energy are required to heal a fracture between the surfaces of the asphalt and the aggregate or within the mastic. The methodology and testing protocol for measuring the surface energy of asphalt are presented. Both the surface energy of dewetting (fracture) and the surface energy of wetting (healing) can be obtained from the contact angle measurement with the Wilhelmy plate method. Ten asphalts were tested; surface energies varied substantially as a function of asphalt composition and the level of aging to which the asphalt was subjected. By using thermodynamic theory, the adhesion and cohesion bonding energy within the asphaltaggregate systems were further analyzed. This analysis has the potential to select the most compatible asphalt—aggregate combination for mixtures. The surface energy is also a very important parameter in the fatigue and healing analysis of the asphalt pavement.
Performance-Graded Binder Specification for Surface Treatments
Authors: Barcena Roberto , Epps Martin Amy , Hazlett Darren
Published: April 2007

Surface treatments have been used by many government agencies as part of their maintenance and rehabilitation programs to improve surface quality and extend the service life of pavements. Traditional specifications for surface treatment binders have failed to characterize materials across the entire spectrum of temperatures experienced during production and construction and in-service and required properties that were not directly related to performance. The Superior Performing Asphalt Pavements (Superpave®) or performance-graded (PG) asphalt binder specification was developed in the 1990s to measure binder properties directly related to hot-mix asphalt concrete (HMAC) performance. This specification included material characterization at low, intermediate, and high temperatures. Direct application of the PG binder specification to binders used in surface treatments is not appropriate because of differences between surface treatments and HMAC with regard to distress types, construction methods, and exposure to environmental conditions. A performance-based specification system for surface treatment binders was developed that maximizes the use of existing equipment required in the PG system for HMAC binders. This new surface performance grading (SPG) specification assumes appropriate design and construction practices and considers only binder properties after construction. The SPG was developed based on the identification of common distresses and the analysis of physical properties at multiple temperatures of surface treatment binders that correlate to these distresses. The final SPG includes limiting values for high-and low-surface pavement design temperatures. Implementation of the SPG specification is recommended after a field validation experiment.
Evaluation of Ramp Control Effectiveness in Two Twin Cities Freeways
Authors: Hourdakis John , Michalopoulos Panos G.
Published: April 2007

Recent public opposition threatened to eliminate ramp control as a traffic management option in the Twin Cities of Minneapolis and St. Paul, which have one of the most extensive ramp control systems in the nation. In response to this, the Minnesota Department of Transportation had to produce tangible independent evidence that ramp metering is effective, to avoid turning off the meters. Simulation is the most widely accepted technique for achieving the stated objectives without turning the metering system off, and therefore it was used in this study. Two freeway sections were selected for detailed testing, and the results along with the methodology are presented here. The results confirm that ramp metering is effective on the ramp and freeway system (not just the freeway), but they also revealed excessive delays on certain ramps that appear to support the concerns raised by the users. Real-life issues related to the simulation implementation process (data collection and filtering, calibration, and interpreting and summarizing results) are also presented. Through the course of this work, simulation reliability was established by defining a successful calibration and validation methodology and by identifying, in the process, certain operational problems related to the deployed surveillance and control system that had been unknown. Finally, a general methodology was developed for evaluation that can easily be adapted to any user-specified control strategy or used to improve an already existing one without field disruptions.
Freeway Travel Time Prediction with State-Space Neural Networks: Modeling State-Space Dynamics with Recurrent Neural Networks
Authors: van Lint J. W. C. , Hoogendoorn S. P. , van Zuylen H. J.
Published: April 2007

An approach to freeway travel time prediction based on recurrent neural networks is presented. Travel time prediction requires a modeling approach that is capable of dealing with complex nonlinear spatio-temporal relationships among flows, speeds, and densities. Based on the literature, feedforward neural networks are a class of mathematical models well suited for solving this problem. A drawback of the feed-forward approach is that the size and composition of the input time series are inherently design choices and thus fixed for all input. This may lead to unnecessarily large models. Moreover, for different traffic conditions, different sizes and compositions of input time series may be required, a requirement not satisfied by any feedforward data-driven method. The recurrent neural network topology presented is capable of dealing with the spatiotemporal relationships implicitly. The topology of this neural net is derived from a state-space formulation of the travel time prediction problem, which is in line with traffic flow theory. The performance of several versions of this state-space neural network was tested on synthetic data from a densely used highway stretch in the Netherlands. The neural network models were capable of accurately predicting travel times experienced, producing about zero mean normally distributed residuals, rarely outside 10% of the real expected travel times. Moreover, analyses of the internal states and weight configurations revealed that the neural networks could develop an internal model linked to the underlying traffic processes.
Transferability of a Stochastic Toll Plaza Computer Model
Authors: Klodzinski Jack , Al-Deek Haitham M.
Published: April 2007

Transferability of the TPSIM toll plaza microsimulation computer model to other toll plazas was explored with 3 days of data collected between 1994 and 2000 at Dean Plaza, an Orlando–Orange County Expressway Authority (OOCEA) toll plaza. TPSIM is a discrete-event stochastic microscopic simulation model that has been previously validated at the 95% confidence level with data from OOCEA’s busiest toll plaza, Holland East Plaza. This model has the capability to accurately model virtually any toll plaza scenario. To apply this model to another toll plaza, a calibration procedure is necessary. To identify the modifications necessary to the input parameters, over 400 simulation runs with the 3 selected days from Dean Plaza were compared and statistically analyzed for accuracy. An experimental design was outlined and followed to accurately account for each trial simulation run during the calibration process. The service time was determined to have the most significant impact on the simulation model in much the same manner as it does in the field. The measures of effectiveness (MOEs) chosen to evaluate TPSIM were throughput, average queuing delay, maximum queuing delay, and total queuing delay. At the 95% confidence level, no significant difference was found in the comparison of field and simulated MOE values for all 3 days. Comparison of the Holland East and Dean Plaza results indicates that the TPSIM simulation model is transferable to another toll plaza with different configurations.
Evaluation of Traffic Flow Analysis Tools Applied to Work Zones Based on Flow Data Collected in the Field
Authors: Schnell Thomas , Mohror Jeffrey S. , Aktan Fuat
Published: April 2007

The Ohio Department of Transportation (ODOT) has identified the maintenance of traffic (MOT) as a top priority to serve the motoring public as part of a department strategic initiative. A key component of this strategy is to ensure that traffic flows efficiently through work zones. Work is described that was performed for ODOT to determine whether commercially available traffic simulation models could be calibrated to yield accurate queue length and delay time predictions for planning purposes in freeway work zones. Four work zones on multilane freeways were selected by ODOT for collection of the calibration data. Traffic flow video records were obtained at the four selected work zones by two ODOT video recording vans equipped with 15-m masts. Traffic flow parameters were extracted from the video records with the Mobilizer-PC software package. The traffic simulation and prediction tools investigated included the Highway Capacity Software (HCS), Synchro, CORSIM (under ITRAF and TRAFVU), NetSim, and a macroscopic model called QueWZ92. Simulation models were constructed with all models for the selected work zones, and the simulated queue lengths and delay times were compared with the data extracted from the field data with Mobilizer-PC. The results of this study indicated that the microscopic simulation packages could not be calibrated to the oversaturated conditions that existed at the work zones. The calibrated microscopic simulation packages underestimated the length of the queues that formed in the real world. The macroscopic QueWZ92 produced more accurate estimates than did the microscopic packages.
Freeway Performance Measurement System: Operational Analysis Tool
Authors: Choe Tom , Skabardonis Alexander , Varaiya Pravin
Published: April 2007

The freeway performance measurement system (PeMS) is a system for all of California. It processes 2 gigabytes/day of 30-s loop detector data in real time to produce useful information. Managers at any time can have a uniform and comprehensive assessment of freeway performance. Traffic engineers can base their operational decisions on knowledge of the current state of the freeway network. Planners can determine whether congestion bottlenecks can be alleviated by improving operations or by minor capital improvements. Travelers can obtain the current shortest route and travel time estimates. Researchers can validate their theory and calibrate simulation models. The use of PeMS in conducting operational analysis, planning, and research studies is described here. The advantages of PeMS over conventional study approaches are demonstrated from case studies on conducting freeway operational analyses, bottleneck identification, level of service determination, assessment of incident impacts, and evaluation of advanced control strategies.
Field Operational Test of Integrated Freeway Ramp Metering/Arterial Adaptive Signal Control: Lessons Learned in Irvine, California
Authors: Arthur MacCarley C. , Mattingly Stephen P. , McNally Michael G. , Mezger Daniel , Moore James
Published: April 2007

A systematic evaluation of the performance and effectiveness of a field operational test (FOT) of an integrated corridor-level adaptive control system was attempted from fall 1994 through spring 1999 in Irvine, California. The FOT was conducted by a consortium consisting of the California Department of Transportation (Caltrans), the city of Irvine, and two private-sector consultants—National Engineering Technologies Corporation and Farradyne Systems, Inc., a division of Parsons Brinckerhoff—with the city of Irvine as the lead agency. The FOT was a cost-share funded by FHWA as part of the Intelligent Vehicle Highway System Field Operational Test Program. The FOT involves an integrated advanced transportation management system, which extends the capabilities of existing traffic management systems in the city of Irvine and in Caltrans District 12. The evaluation originally entailed both a technical performance assessment and a comprehensive institutional analysis. This report of the Irvine FOT does not constitute a technical evaluation because of the failure of any of the planned technologies to be successfully implemented in the field. Because of the extended time frame associated with the project and the significant range of technical and institutional issues associated with the development and eventual failure of the FOT, a summary of project development, institutional barriers, and lessons learned is provided.
Integrated Control Strategies for Surface Street and Freeway Systems
Authors: Tian Zong Z. , Balke Kevin , Engelbrecht Roelof , Rilett Larry
Published: April 2007

Freeway ramp metering often exists in the vicinity of a signal-controlled diamond interchange, at which the surface street system and the freeway system intersect. Even though both systems are controlled by traffic signals, they primarily operate independently of one another. The integrated operations of a surface street system and a freeway system were studied with VISSIM, a microscopic simulation model. A traffic network consisting of a surface street and a freeway segment was constructed in VISSIM. The surface street and freeway are connected through a diamond interchange with on-ramps and off-ramps. The objective of the study was to develop an integrated control algorithm for both the diamond interchange signal and the ramp-metering signal. The proposed control algorithm, including an adaptive diamond interchange control and a traffic-responsive ramp-metering control were programmed with VISSIM’s vehicle-actuated programming, which serves as an external control function for the simulation model. Preliminary tests of the proposed control algorithm indicated improved operations for both the surface street system and the freeway system. Traffic operations were significantly improved compared with nonadaptive diamond control and static ramp-metering control. Although similar performance measures were found (with the particular scenarios evaluated) with no-metering control, with the existing traffic-responsive ramp-metering control, and with the proposed traffic-responsive rampmetering control, the proposed control algorithm has more flexibility and may be adapted over a broader range of traffic flow conditions.
Monitoring Commuter Congestion on Surface Streets in Real Time
Authors: Perrin Joseph , Martin Peter T. , Coleman Brad
Published: April 2007

As public agencies focus on optimized signal timing to reduce congestion, few have the ability to monitor network operations in real time. Little work has been done to provide a graphic presentation of surface street congestion. A way is introduced here to identify and monitor commuter congestion on surface street arterials without using specialized equipment. Existing system detectors have been combined with the signal timing information to classify traffic congestion levels. The Utah Department of Transportation Traffic Operation Center is incorporating the results to provide a real-time arterial congestion map. Occupancy, flow, and signal information are reported to the traffic operation center every 5 min. Then, a commuter congestion algorithm compares the actual measured volume with an estimated approach capacity. It is inappropriate to assume a fixed-green time per cycle because the network’s signalized intersections operate on coordinated–actuated control. The algorithm compares the estimated approach capacity with the measured approach volume to give an estimated real-time volume/capacity ratio. The approach capacity is estimated by an equation developed through simulating network intersections under a range of congested conditions with various cycle lengths and approach green times. The methodology has been verified against field data from congested locations with actual volume and signal timing during peak periods. The predicted approach volumes were within 5% of observed congested conditions. This method allows traffic engineers to monitor and identify the congestion of a signal-controlled surface street network in real time without the need for new technologies.
Adaptive Signal Control System with Online Performance Measure for a Single Intersection
Authors: Liu Henry , Oh Jun-Seok , Recker Will
Published: April 2007

An adaptive signal control system with an online signal performance measure is introduced. Unlike conventional signal control systems, the proposed method uses real-time delay estimation and an online signal timing update algorithm. As a signal performance measure, intersection delay for each phase is measured in real-time via an advanced surveillance system that reidentifies individual vehicles at upstream and downstream stations by using vehicle waveforms obtained from advanced inductive loop detectors. In each cycle, the signal timing plan is optimized based on the delay estimated from the vehicle reidentification technology. The main thrust of the algorithm is the online control capability utilizing direct intersection delay measures. A description of the overall control system architecture and the optimization algorithm is addressed. Performance of the proposed system is evaluated with a high-performance microscopic traffic simulation program, Paramics, and the preliminary results prove the promising properties of the proposed system.
Optimizing Traffic Network Signals Around Railroad Crossings: Model Validations
Authors: Zhang Li , Hobeika Antoine G. , Ghaman Raj
Published: April 2007

A model entitled SOURCAO (signal optimization under rail crossing safety constraints) is discussed. There are two objectives in SOURCAO design: highway rail grade crossing (HRGC) safety consideration and highway traffic delay reduction around the crossings. The first step in SOURCAO is to choose a proper preemption phase sequence to promote HRGC safety. This is done by the inference engine in an intelligent agent. The second step in SOURCAO is to find the optimized signal phase length to reduce highway traffic delay. The optimization process uses an objective function of the network traffic delay. The delay is approximated and represented by a multilayer perceptron neural network. The system inputs are online surveillance detector data and HRGC closure information. The system architecture of SOURCAO is briefly discussed. Various types of surveillance schemes in the proposed delay model are introduced. Emphasis is on validating the various models applied in SOURCAO. First, the proposed delay model is compared with queue delays obtained from the TSIS/CORSIM traffic simulation package. Second, the neural network delay forecast is verified through a cross-validation procedure. Finally, the objectives of SOURCAO are evaluated by TSIS/CORSIM. The average network delay for 20 runs of simulation is reduced over 8% ( P =0.05; t-test), and the unsafe queue time of the highway vehicle on HRGC in a test case is reduced.
Toll Road Concessions in Argentina: What Can Be Learned
Authors: Nicolini-Llosa José Luis
Published: April 2007

The toll road concession experience in Argentina during 1990 to 2001 is reviewed. Some guidelines are suggested for the future in terms of thorough bidding qualification procedures, competitive bidding with simple and clear documents, prevention as regards construction firms controlling the concessionaire, agreements designed to reduce renegotiations to a minimum, renegotiations open to international auditing, optimization of risk allocation between the users and the concessionaire, prohibition of contract extension, performance rather than profitability controls, users’ control with strong government support, toll collection and investment policy integration over the road network, congestion pricing, and intelligent transportation systems traffic management.
Highway Costs and Efficient Mix of State and Local Funds
Authors: Levinson David , Yerra Bhanu
Published: April 2007

Governments and transportation networks are both hierarchically organized. Some state governments finance most of their highways, whereas in other states similar roads are financed locally. Larger governments attain scale economies. However, they also tend to be more bureaucratic and have higher operating costs, all else being equal, because of problems such as span of control. A study was done to relate highway expenditures with the share of expenditure by state governments to determine how governments should allocate expenditure on all roads in a state. Highways are divided into two hierarchical classes (higher and lower), governments into two layers (state and local), and costs into capital and operations and maintenance. Regression models to predict different highway expenditures on each highway class as a function of utilization, capacity, and funding shares are estimated. It is found that there is a share of expenditures by each level of government for each highway class that results in a minimum expenditure for each funding category (capital and operations). That minimum is not very far from typical state and local mixes found in many states. The results can be applied in formulation of efficient network financing arrangements. Policies can be formulated that would help adjust the financial responsibilities of transportation networks between government layers.
State Route 91 Value-Priced Express Lanes: Updated Observations
Authors: Sullivan Edward C.
Published: April 2007

Recently over 5 years of field observations were concluded of the valuepriced express lanes that opened December 27, 1995, in the median of State Route 91, in Orange County, California. Data collection, covering about a year and a half of observations to establish baseline conditions before opening day, included traffic measurements, vehicle occupancy counts, transit ridership, and comprehensive travel surveys of current and former commuters. The corresponding data analysis included the calibration of choice models of route, occupancy, transponder acquisition, and time-of-day behavior of commuters and the estimation of air pollution emissions. Findings are presented on traffic trends, toll lane use, travelers’ responses to changing congestion and tolls, shifts in ridesharing and transit use, shifts in trip purpose, differences associated with income and other demographics, public opinion, collision experience, and the results of choice and emissions modeling. As the first practical application of value pricing in the United States, the State Route 91 express lanes provide many important insights, both technical and institutional, some of which are relevant to the implementation of value-pricing projects in other locations.
San Diego’s Interstate 15 Congestion Pricing Project: Traffic-Related Issues
Authors: Supernak Janusz , Golob Jacqueline , Golob Thomas F. , Kaschade Christine , Kazimi Camilla , Schreffler Eric , Steffey Duane
Published: April 2007

Traffic-related findings from the evaluation of the Interstate 15 (I-15) congestion pricing project are summarized. The project was a 3-year demonstration that allowed single-occupant vehicles (SOVs) to use the existing I-15 high-occupancy-vehicle (HOV) lanes, known as the I-15 express lanes, for a fee. San Diego State University conducted an independent, multielement evaluation of the I-15 pricing project to assess its impacts for both the ExpressPass and FasTrak phases of this demonstration. The primary project goals were ( a) to maximize use of the existing I-15 express lanes, ( b) to test whether allowing solo drivers to use the express lanes’ excess capacity could help relieve congestion on the I-15 main lanes, ( c) to fund new transit and HOV improvements in the I-15 corridor, and ( d) to use a market-based approach to set tolls. At the end of 1999, the I-15 pricing project was meeting its primary objectives. There was substantially better utilization of the express lanes. Both ExpressPass and FasTrak were feasible solutions for generating sufficient revenue to fund the new express bus service, called Inland Breeze. Neither ExpressPass nor FasTrak negatively affected carpool volumes on the express lanes; FasTrak was able to redistribute volumes from the middle of the peak to the peak shoulders. Free-flow conditions were maintained at virtually all times. The project’s primary benefit was the reliability of ontime arrival for users. The project was also able to slightly alleviate congestion on the I-15 main lanes. SOV violation rates in the I-15 express lanes remained substantially below the preproject level. Also discussed are the air quality, delay, and park-and-ride impacts of the project.
Double Cordon Tolls in Urban Areas to Increase Social Welfare
Authors: Santos Georgina
Published: April 2007

A second-best traffic demand management policy, cordon tolls, is considered. Double cordons are simulated for seven English towns. It is found that a second, outer cordon implemented jointly with an inner cordon surrounding the city center enhances the increase in social welfare in comparison with a single inner cordon. Although other social and political considerations such as potential revenues and distributional effects may persuade policy makers to implement higher or lower charges, a method is proposed for deciding on the optimal combination of tolls, which is defined as the combination that maximizes the increase in social welfare for a given cordon location, social welfare being equal to the sum of individual utilities minus the sum of individual costs.
Choice Models of Route, Occupancy, and Time of Day with Value-Priced Tolls
Authors: Yan Jia , Small Kenneth A. , Sullivan Edward C.
Published: April 2007

Choice models were developed on the basis of data from surveys of commuters on California State Route (SR) 91, the nation’s first operational value-priced toll facility, in 1999. The models represent route choice among the value-priced SR 91 express lanes, the parallel nontoll freeway, and the Eastern Toll Road, a roughly parallel fixed-toll highway. The models also represent commuters’ choice of vehicle occupancy (single occupant, two-person groups, and groups of three or more persons), time of day of travel, and whether to obtain the transponder needed for electronic toll collection. The models show implied values of time for commuters in the range of $13 to $16 per hour and toll elasticities for express-lane traffic of 0.7 to 1.0, depending on the time period involved. Results demonstrate that there is scope for adjusting toll schedules, even in as small as 1-h increments, in order to regulate demand.
Intensive Customer Feedback to Improve Delivery of Highway Maintenance Programs in Pennsylvania
Authors: Poister Theodore H. , Harris Richard H. , Robinson Joseph , Reeder Jill S.
Published: April 2007

The Pennsylvania Department of Transportation (PennDOT) has long been a leader among state transportation departments in the area of quality improvement and customer service. As part of this effort, PennDOT recently overhauled its annual survey of motorists to solicit more specific and more usable feedback in order to improve the delivery of highway maintenance services at the district and county levels. The background of this upgraded survey is provided, the current methodology and instrument are described, initial findings from the first year of field work are presented, and the management uses of the results, intended to strengthen service delivery, are discussed. The initial findings resulted in substantial variation in motorists’ ratings among the three classes of highway and from county to county across the commonwealth. On balance, Pennsylvania motorists gave PennDOT highways a grade of C+, which represents a passing grade but still leaves considerable room for improvement. The results were forwarded to each district office in the form of a “report card” displaying performance grades in the three dimensions of ride quality, traffic flow, and safety for each of the three classes of roads. With these results, the districts set targets for improvement on each survey item that is linked to a strategic focus area of the annual business plans of both PennDOT and the district, thus building motorist satisfaction into the overall work program. In addition, county maintenance offices were provided a report card on the items clearly within their span of control. They too used the results to influence county maintenance work plans.
Economic, Social, and Technological Forces Shaping Road Administrations
Authors: Cox John B. , Douglas-Crane Miranda
Published: April 2007

A conceptual model of the development of road administrations that is driven by economic, social, and technological forces is described. Different economies based on agriculture and industry or on services and knowledge produce different road transport characteristics. Technological change affects the demand among transport modes, and recent developments in communications and information technology are now having a major effect on road transport systems and the internal management of road administrations. Road networks undergo different phases of development, categorized as birth, growth, upgrading, and maturity. There is a correlation between economic and social development and these road network phases, with developing countries mainly involved in network growth and developed countries mainly focused on network upgrading. Some countries are observing a slowing of increases in car ownership and road travel demand as they move into a more mature phase. Road administrations have responded to these external forces as their road networks have developed. Institutional reform has occurred to bring clearer lines of accountability in policy, regulation, funding, procurement, and delivery functions. Further reform is occurring to take account of the greater involvement of both the community and the private sector in the planning, funding, and delivery of road transport improvements. There is an ongoing need for road administrations to develop different capabilities as road networks develop. The predominant skill base shifts from engineering during road network growth to management using community-based performance indicators during the network upgrading phase. In the mature phase still greater management skills are needed to integrate road transport with other transport modes, partner with the private sector, and incorporate new information and communication technologies into management processes.
New Regional Transportation Organizations: Old Problem, New Wrinkle?
Authors: Gifford Jonathan L. , Pelletiere Danilo
Published: April 2007

As attention turns to the operations and management of the nation’s highway infrastructure, regional operating organizations (ROOs) have increasingly become part of the transportation scene. Many ROOs are housed in new organizations, which are essentially voluntary alliances between state and local operating agencies in a region. The history of regional organizations and the so-called “new regional transportation organizations” that are being created around operations and management tasks is examined. Three questions are asked: ( a) Why are new organizations being created when regional organizations already exist? ( b) How do new organizations differ from those that currently exist? ( c) How will the new organizations operate within the existing metropolitan context as they develop and mature? The conclusion is that the success of these organizations depends on how they navigate the transition from being new organizations whose focus and jurisdiction do not adequately correspond to regionwide operations issues to being full-fledged regional organizations in an environment populated by existing metropolitan planning organizations (MPOs) and regional authorities. The particular challenge is how these organizations will be able to grow to meet region-specific needs and challenges while providing sufficient accountability and consistency to facilitate federal participation. The history of MPOs suggests that universal and far-reaching federal mandates may not be the best strategy to achieve these goals.
Wisconsin’s Local Roads and Streets Council: Prototype for Intergovernmental Cooperation and Decision Making
Authors: Forlenza Mary , Gent Chariti
Published: April 2007

Trends in the devolution of power from the federal to the state and local levels during the last two decades have sparked considerable research, discussion, and action on a variety of policy topics; transportation is no exception. Of particular interest is the way in which communication, education, and outreach among various levels of government are being made more seamless in the face of institutional change. In response, many states and local governments are forming partnerships to facilitate communication and outreach so as to improve decision making. In Wisconsin, the state department of transportation is partnering with local officials to develop policy alternatives that enhance the quality of Wisconsin’s local roads and streets. This state-local partnership, the Local Roads and Streets Council (LRSC), works to facilitate and streamline communication, education, and outreach efforts in order to maximize input from a variety of stakeholders throughout the state. Not only does facilitating communication and outreach help to ensure that the most appropriate transportation policy alternatives are developed, but creating formal avenues for effective and efficient discussion among citizens and their government regarding various policy solutions is at the core of the democratic process. The way in which the LRSC is organized, operated, and maintained is summarized, and information about the benefits, accomplishments, and challenges facing a state and local decision-making partnership of this kind is provided. It is hoped that this overview provides a prototype for other states and issue areas with regard to communication, education, and outreach across jurisdictional lines in the face of increasing institutional change.
Education of Transportation Planning Professionals
Authors: Handy Susan , Weston Lisa , Song Jumin , Maria D. Lane K.
Published: April 2007

The practice of transportation planning at the regional level has evolved substantially over the past several decades. Once defined as largely a technical exercise, in which the calculation of required roadway capacity was the preeminent activity, transportation planning now encompasses a wide range of sometimes conflicting problems and demands, from growing levels of congestion and worsening air quality to neighborhood preservation and social equity concerns. But are the curricula in the planning and engineering programs that educate and train transportation professionals adequately preparing them for these new challenges? The objective of the study summarized was to compare the kinds of knowledge and skills important to transportation professionals today with the kinds of knowledge and skills that planning and engineering programs provide their students in order to highlight areas for improvement and suggest ways to enhance the education of transportation professionals. The research involved several components: a literature review of transportation education and planning education, an analysis of planning requirements in federal transportation authorization legislation, construction and analysis of a database of course offerings in the area of transportation planning provided by planning programs and selected transportation engineering programs, a survey of transportation planning professionals, and interviews with selected transportation planning educators and professionals. Some of the key findings from those efforts are summarized, and several important issues are suggested that transportation educators should address to improve the quality of education for transportation planning professionals.