California Department Of Transportation Research Articles

Procurement Contracting with Time Incentives: Theory and Evidence

In public sector procurement, social welfare often depends on the time taken to complete the contract. A leading example is highway construction, where slow completion times inflict a negative externality on commuters. Recently, highway departments have introduced innovative contracting methods based on scoring auctions that give contractors explicit time incentives. We characterize equilibrium bidding and efficient design of these contracts. We then gather an extensive data set of highway repair projects awarded by the California Department of Transportation between 2003 and 2008 that includes both innovative and standard contracts. Comparing similar contracts in which the innovative design was and was not used, we show that the welfare gains to commuters from quicker completion substantially exceeded the increase in the winning bid. Having argued that the current policy is e ffective, we then develop a structural econometric model that endogenizes participation and bidding to examine counterfactual policies. Our estimates suggest that while the current policy raised welfare by $359M (6.8% of the total contract value), the optimal policy would raise it by $1.52B (29%).

CalBack: Enhancing Caltrans Mechanistic-Empirical Pavement Design Process with New Back-Calculation Software

In 1996, California Department of Transportation (Caltrans) initiated an extensive project to develop mechanistic-empirical (ME) pavement design and analysis tools, which will help state design engineers incorporate the impact of new products and technologies, increased traffic volumes and axle loading, and variable climatic conditions. As part of the development of new ME design procedures, Caltrans is developing a suite of dedicated software. CalME is a ME design program for flexible pavements that parallels the NCHRP 1-37A (MEPDG) and is calibrated for California conditions. CalBack is a sophisticated back-calculation program that contains specific features pertinent to California and is designed to work standalone, or in concert with CalME. CalBack is a unique and important addition to the existing knowledge base in that it possesses multiple data input/output methods, several new analytical modeling methods, and numerous user performance options. This paper describes the successful development and implementation of CalBack in three ways: (1) why and how Caltrans developed CalBack; (2) how CalBack functions; and (3) representative studies that show how well the software performs. Application of CalBack in several California projects, including the case studies presented in this paper, has shown that back-calculated moduli for different layers in the flexible and rigid pavement systems agreed reasonably well with laboratory measured values. Furthermore, the importance of avoiding temperature gradients when evaluating portland cement concrete pavements with the falling weight deflectometer is also well captured by CalBack.

Quality Control–Quality Assurance Sampling Strategies for Hot-Mix Asphalt Construction

The effects of sampling strategies and size on statistically based decision making in hot-mix asphalt (HMA) construction are presented. For sample sizes agreed on by the agency and the contractor, an acceptable level for an HMA mix parameter is determined with risk balanced between the two organizations. With increased emphasis on specific performance requirements, the use of performance tests on HMA specimens prepared from in situ samples is developing. Examples include direct measures of mix stiffness and permanent deformation characteristics. A measure of rutting resistance, the stabilometer S-value, is used by the California Department of Transportation (Caltrans) for quality control–quality assurance (QC/QA) projects. Although the S-value was used for this simulation because extensive tests were available, this approach is applicable to any performance measures already in use, such as HMA thickness or compacted air void content. A sampling scheme and sampling size through statistical simulation of a fixed length of a one-lane-width placement of HMA are discussed. Sample size is based on the combination of the sample size of the contractor and that of the agency to balance the risk to both organizations and results in a mix that will meet the minimum performance requirement. An example is given for the placement of 15,000 tons of HMA according to Caltrans QC/QA requirements. For this total tonnage, the contractor and agency are respectively assumed to perform a specific number of stabilometer tests for QC and QA. Results of the simulation yield the average stabilometer value that the contractor must obtain to ensure that the quality requirement, that is, the minimum S-value, is met.

Noise benefits of asphalt pavements—Trends at ages up to 52 months

The U.S. DOT Volpe Center Acoustics Facility, in support of the California Department of Transportation, is participating in a long-term study to assess several types of pavement for the purpose of noise abatement. On a 6.4-km (4-mi) stretch of a 2-lane highway in Southern California, several asphalt pavement overlays are being examined. Acoustical, meteorological, and traffic data are collected in each pavement overlay section, where microphones are deployed at multiple distances and heights. Single vehicle pass-by events are recorded primarily for three vehicle types: automobiles, medium trucks, and heavy trucks. Data are analyzed to determine the noise benefit of each pavement as compared to the reference dense-graded asphalt pavement; this includes a modified Statistical Pass-By Index as well as average A-weighted maximum sound levels for each vehicle type. In addition, 1/3-octave band data are examined.

Precipitation Variation and the Identification of High-Risk Wet Accident Locations in California

To improve safety continually along California's roadways, the California Department of Transportation (Caltrans) developed a list of high-collision concentration locations that required further evaluation and treatment. One version of this list, Wet Table C, analyzes only wet accidents (those during or following precipitation). In developing Wet Table C, wet percent factors–-which quantify the proportion of time per year during which pavement is damp enough to cause traffic accidents (measured on an hourly basis)–-are employed. These factors were originally developed at the county level (i.e., one factor per county). A recent updating of factors allowed for their development at a finer spatial level (quarter-mile segments of roadway). This research examined whether such finer-resolution factors produced different results when incorporated into the Caltrans Wet Table C process. Results of McNemar tests indicated that there was no statistical difference between lists produced using a singular wet percent factor and ones produced using finer resolution factors.

Long-term noise performance of open graded asphalt concrete (OGAC)—Results of 10-year long study

During June and July of 1998, an open grade asphalt concrete (OGAC) pavement overlay was applied to a 5.6-mile (9-kilometer) stretch of aged dense graded asphalt concrete (DGAC) along Interstate 80 to the east of Davis, California. Beginning in 1998, noise conditions have been monitored by Illingworth & Rodkin as part of an ongoing study conducted by the California Department of Transportation (Caltrans) to evaluate the long-term effects of highway pavement types on traffic noise. Noise evaluation of the OGAC pavement was conducted using the continuous flow traffic time integrated method (CTIM) of measuring traffic noise levels at locations adjacent to the roadway and the on-board sound intensity (OBSI) method of measuring tire-pavement noise close to the tire-pavement interface. Measurements were conducted on more than 70 days over the past 10 years, resulting in a total of more than 275 hours of noise measurements and generating an extensive data set. This paper focuses on the results of the OBSI and CTIM measurements. Results discussed in this paper include; 1) a comparison of the acoustical performance of the OGAC pavement to the baseline DGAC and other pavement types, 2) a description of the effects of aging of the OGAC pavement on acoustical performance, and 3) a description of seasonal trends in noise levels based on the data set. Based on the noise measurements, the OGAC pavement initially resulted in noise levels that were about 7 dB below those measured for the baseline DGAC pavement and maintained these quieter characteristics through 10 years, with only a slight increase in noise levels over time.

Comprehensive Laboratory Testing and Performance Evaluation of Recycled Pulverized Hot-Mix Asphalt Material

The California Department of Transportation is studying a pavement rehabilitation strategy that involves the pulverization of failed hot-mix asphalt (HMA) pavements and uses the pulverized material as a granular base material in the reconstruction of the pavement. Advantages of this technique include a reduction in the use of virgin aggregates, a reduction in the amount of construction traffic, and removal of the potential for reflective cracking from the existing pavement layers. The construction and performance of four pilot projects in District 2 in northeastern California were used to evaluate this rehabilitation strategy. The characteristics and performance of the pulverized material were evaluated by comprehensive laboratory and field testing. The laboratory testing covered basic index tests and comprehensive triaxial testing. Multistage repeated-load permanent strain triaxial tests on different material gradations, stress levels, moisture contents, with and without stabilizing agents (lime and cement), and the degree of compaction were used to investigate the resilient and permanent strain characteristics. Testing was conducted on saturated samples to evaluate the effect of saturation on the pulverized material. The effects of the number of load repetitions were also investigated. The performance of the pulverized material was also compared with two typical virgin aggregate base materials from California. A life cycle cost analysis of this rehabilitation technique when compared to a typical HMA overlay showed that the recycling option was cheaper in both the short term and over the life of the pavement.

Overcoming Roadblocks to Innovation

This paper examines the experience of the California Department of Transportation (Caltrans) in three recent innovations developed at its Division of Research and Innovation. Although these innovations promised significant returns on investment, their deployment faced serious challenges, which motivated this research. A literature review was conducted and professionals were interviewed to analyze the roadblocks. The innovations, roadblocks, successful mitigation measures, and lessons learned in each case are presented. The first case is Sensys, a compact, low-cost, wireless traffic-sensing system that can replace more expensive inductive loops. The second case is the Construction Analysis for Pavement Rehabilitation Strategies software, which simulates highway construction and traffic activities at construction zones and predicts traffic delays associated with simulation scenarios, to optimize construction timing and quality and minimize construction costs and effect on traffic. The third case is the Balsi Beam, a mobile frame designed to protect highway workers. Findings show that deployment faced roadblocks because ( a) transportation projects were complex, multifaceted, and interjurisdictional with many players having different interests; ( b) multiple layers of decision making sometimes lacked logic; ( c) public-sector procurement was driven by competitive, multiple low-bid processes that often infringed on intellectual property rights; ( d) public agencies resisted change; and ( e) risk-averse executives hesitated to implement new innovations. To mitigate roadblocks, a systems engineering process is advocated, one that ensures that customers are included in all phases so that the final product meets their needs and satisfies their requirements. Findings underline the need to interconnect researchers, developers, operators, and decision makers by improving communications at all levels and stages. There is need for timely establishment of criteria for evaluating innovations and for creation of innovative champions.

An Assessment of Mosquito Production and Nonchemical Control Measures in Structural Stormwater Best Management Practices in Southern California

A 3-year study was conducted to assess mosquito production in structural stormwater Best Management Practices (BMPs) installed by the California Department of Transportation in San Diego and Los Angeles Counties. Thirty-seven BMPs were monitored weekly for presence and relative abundance of immature mosquitoes and for conditions conducive to mosquito production. Species identified were Aedes squamiger, Anopheles franciscanus, An. hermsi, Culex quinquefasciatus, Cx. stigmatosoma, Cx. tarsalis, Culiseta incidens, and Cs. inornata. Structures designed with accessible, permanent sources of standing water in sumps, vaults, or basins were observed to support immatures all year. In BMPs intended to drain rapidly and completely, observed larval habitats resulted from design features, component failure, construction flaws, and non-stormwater runoff flows. Specific nonchemical mitigation measures to minimize or eliminate mosquito production were developed, implemented, and evaluated. This study provides a 1st assessment of mosquito production, species composition, and nonchemical control measures in structural stormwater BMPs in southern California.

Global Trade Comes Home: Community Impacts of Goods Movement

For many U.S. residents, 2007 was a year of heightened awareness of some of the problems of global trade. Extensive recalls of melamine-tainted pet food in the spring followed by even larger toy recalls in the summer and fall raised consumer concerns about how the United States can ensure the safety of products shipped in from overseas. The Salt Lake Tribune and the Wall Street Journal detailed injuries and illnesses threatening the health of Chinese workers making products for export to the United States. And on 15 December 2007, a New York Times feature detailed the practice of farming fish in toxic Chinese waters for export to the United States and other countries. While these news stories demonstrate some of the pitfalls of globalization, much less attention has focused on air pollution and other community-level impacts in the United States, as toys, electronics, food, and other imports travel through ports, then to trucks, trains, warehouses, and stores in a complex system called “goods movement.” Along the route, residents are exposed to diesel exhaust and other vehicle emissions, noise from truck-congested roads, bright lights from round-the-clock operations, and other potential health threats. Transportation experts refer to these impacts simply as “externalities” of transport, but to community residents they can directly harm the quality of daily life. As ports and goods movement activity expands throughout the United States, a major challenge is how to make its health and community impacts a more central part of policy discussions.

Calibration of Mechanistic-Empirical Models for Flexible Pavements Using California Heavy Vehicle Simulators

Calibration of mechanistic-empirical models for pavement design is a very complex process. The heavy vehicle simulator (HVS) is ideal for the first step in this calibration process. The short test section can be carefully constructed with well-characterized materials and instrumented to measure the pavement response. The climatic conditions may be controlled or monitored closely, all load applications are known exactly, and perhaps most important, the pavement may be tested until it fails. This overcomes the problems of real pavements, which have uncertainties with regard to materials, loads, and climatic conditions and which are normally designed with a high reliability leading to very few failures. The mechanistic-empirical models of an incremental-recursive computer program, known as CalME, have been initially calibrated using data from 27 flexible pavement test sections tested with the two HVSs owned by the California Department of Transportation. Most sections were instrumented with multidepth deflectometers to compare the measured pavement deflections (at several depths) to the deflections predicted by the mechanistic model. Resilient deflections were compared for the complete time history of each test, and each test was carried to failure in regard to rutting (12.5 mm), cracking (2 m/m2), or both. This involved the calibration of models for changes in layer moduli, including the effects of asphalt fatigue. The comparison of measured and predicted response is essential to ensure that the pavement response is predicted reasonably well by the mechanistic model. Once this was achieved, models for permanent deformation of the individual pavement layers were calibrated against the measured permanent deformation of the layers, again using the complete time history of each test.

Comparison of Surface Characteristics and Pavement/Tire Noise of Various Thin Asphalt Overlays

ABSTRACT Traffic noise has become a major concern in the last decade and many countries have been looking for solutions to reduce noise levels. The California Department of Transportation (Caltrans) has been using different open graded mixes to reduce highway noise levels and improve wet weather driving conditions. There is a need to identify their noise reduction properties, durability, and safety, and to compare these with other asphaltic mixes. Caltrans initiated a long-term program to investigate and monitor field performance of different open graded mixes and other commonly used asphalt surface mixes. This paper summarizes part of the first-year measurements of relevant parameters from asphalt pavements with different surface mixes. It was confirmed that open graded mixes generally reduce the tire/pavement noise level, and the amount of reduction is correlated with air-void content and surface texture.

Streamlined Strategies for Faster, Less Traffic-Disruptive Highway Rehabilitation in Urban Networks

The need for faster, less traffic-disruptive rehabilitation for aging highway infrastructure is an emerging concern for many state highway agencies. In response to this concern, the California Department of Transportation (Caltrans) launched the Long-Life Pavement Rehabilitation Strategies (LLPRS) program in 1998 to rebuild 2,800 lane kilometers of high-volume urban freeway with premium pavements that will last 30+ years and require minimal maintenance over their service life. This paper presents innovative strategies and technologies for achieving faster project completion with less traffic disruption as applied on three experimental LLPRS projects. The research team and the Caltrans project team used Construction Analysis for Pavement Rehabilitation Strategies (CA4PRS) software from the initial planning and design stages to implement the most economical rehabilitation strategies for the projects. The postconstruction analysis of all three LLPRS projects, made with data collected during construction, revealed a close match with the preconstruction schedule estimate generated by CA4PRS, validating the software's scheduling reliability. Incentive-disincentive contractual provisions proved effective for shortening project duration on all three LLPRS projects, which were time critical because of their heavy traffic volume. Resultant traffic data demonstrate the importance of a public outreach campaign that convinced motorists to use alternative routes or to adjust their commuting modes, resulting in significantly lower traffic demand in the construction work zone. The strategies and lessons addressed in this paper will help state highway agencies and contractors maximize construction productivity for early project completion and minimize inconvenience to the traveling public.

Marked-Crosswalk Dilemma

Primarily in response to several landmark safety studies, and as an official or unofficial policy, many agencies across the United States have elected to remove marked crosswalks at uncontrolled intersections or have shown resistance to installing them in the first place. This approach results in unacceptable pedestrian mobility restrictions, yet such restrictions are often not considered in policy making. As such, there is a need for roadway system owners to develop strategic safety guidelines to address the marked-crosswalk dilemma. Since 2005, the Traffic Safety Center at the University of California, Berkeley, in a study funded by the California Department of Transportation, has focused on developing a better understanding of driver and pedestrian behavior and safety in both marked and unmarked crosswalks in an effort to recommend more informed crosswalk policies. The study was designed to fill key gaps in the literature by analyzing pedestrian and driver behavior and knowledge of right-of-way laws regarding marked and unmarked crosswalks. The study also focused on driver and pedestrian behavior in multiple-threat scenarios, the most common type of pedestrian collisions at uncontrolled intersections. Results are summarized from field observations of driver and pedestrian behavior at marked and unmarked crosswalks on low-speed two-lane and multilane roads. The behavioral observations are interpreted in light of findings reported by Mitman and Ragland from surveys and focus groups regarding driver and pedestrian knowledge of right-of-way laws. The discussion concludes with recommendations for a comprehensive crosswalk safety policy to strategically address crash risk at uncontrolled crosswalks.

Transportation Benefit–Cost Analysis

The California Department of Transportation (Caltrans) assesses more than 100 transportation projects annually for its State Transportation Improvement Program, one of the largest such programs in the country. Caltrans relies on benefit–cost analysis as one of several performance factors, and evaluations must be completed in a few weeks. Caltrans developed a spreadsheet model, Cal-B/C, to provide a common benefit–cost framework and facilitate rapid project evaluation. The model is based on extensive theoretical reviews but is intended to keep the analysis simple. Cal-B/C incorporates rules of thumb to accommodate projects with little upfront evaluation. It can also use summary data from microsimulation and travel demand models. Although this design supports analysis with minimal data, Caltrans has found that the need for accurate and consistent data complicates project evaluation. This paper presents an example of how California applies benefit–cost analysis for objective project appraisals. The paper describes the motivation for Cal-B/C, its structure, applications, and continued evolution. Particular attention is paid to a recent evaluation of projects proposed for a $4.5 billion infrastructure bond measure. The paper also offers lessons for applied transportation performance analysis and proposes areas for further research.

Productivity Aspects of Urban Freeway Rehabilitation with Accelerated Construction

Over the last 5years the California Department of Transportation (Caltrans) has completed three experimental long-life urban freeway rehabilitation projects by utilizing a fast-track (accelerated) construction approach of around-the-clock operations under extended closure. This paper presents the fast-track rehabilitation approaches and the as-built production rates of major rehabilitation operations monitored at the three experimental projects. The monitoring results show that the contractor’s production rates varied considerably depending upon the construction logistics, material delivery and hauling methods, lane-closure tactics, and/or pavement designs being implemented. A higher production rate and a noticeable “learning-curve effect” were observed when full-width rehabilitation was compared with partial-width rehabilitation, when continuous lane reconstruction was compared with random slab replacements, and when full roadbed closures were compared with partial lane closures. Findings in this study suggest that Caltrans should evaluate project-specific conditions and constraints, which might restrict use of a preferred rehabilitation scheme, by taking production rate variances into account when establishing schedule baselines of construction staging plans and incentive/disincentive contracts for urban freeway rehabilitation projects.

Vehicle Infrastructure Integration Test Beds Planned for Detroit

In this article, the author describes a number of tests conducted by the Michigan Department of Transportation (MDOT) regarding Vehicle Infrastructure Integration (VII). The tests, conducted in the Detroit area, collect vehicular information such as speed of travel, road surface conditions, windshield wiper use, air temperature, and shock and antilock brake use. Intelligent Transportation Systems (ITS) concepts such as VII are implemented in order to increase both mobility and safety. Using a dedicated short-range radio system (DSRC), which links cars to one another via vehicle-to-vehicle as well as to wayside hubs, researchers hope to determine whether a fast moving vehicle can engage in local wireless network communications as effectively as stationary objects. Other such VII tests are being conducted in the San Francisco Bay Area by the California Department of Transportation (Caltrans) and the University of California, Berkeley.

Taking the Leap into E-Learning

In 2005, the University of California at Berkeley Institute of Transportation Studies Technology Transfer Program, with funding from the California Department of Transportation, began development of an online training program for local agencies in California. Training was developed from existing classroom courses for delivery with the web-based WebEx platform. Phase 1 (the topic of this paper) focused on delivery of synchronous (live) sessions over the Internet. Phase 2 will translate these sessions into asynchronous training available 24/7 over the web. Training topics included federal aid compliance, the Americans with Disabilities Act, traffic signal timing, and transportation planning. Lessons learned during Phase 1 include how to select software platforms, how to select appropriate course content for online delivery, how to identify and select instructors who will be able to teach online successfully, and how to work with online learners.

Dashboards for Transportation Operations

Dashboards are an increasingly common method for executives in the private sector to monitor the effect of business decisions on business operations. These dashboards integrate business intelligence databases into relatively simple web-based reporting mechanisms accessible to multiple decision makers. Some states in the public-sector transportation arena have developed dashboards to monitor delivery on relatively long-term agency processes, such as project budget and schedule metrics. Few efforts have focused on monitoring relatively short-term operational performance measures. Berkeley Transportation Systems, Inc., has worked with the California Department of Transportation to develop an operational performance measure–based dashboard for transportation agency executives using the Performance Measurement System. This paper outlines an application of this dashboard to a specific agency program aimed at improving traffic detector health.

Automated Consensus-Based Data Verification in Caltrans Detector Testbed

A practical need to assess the accuracy and attributes of each of the many types of roadway sensors and detectors motivated the California Department of Transportation to construct a traffic detector test bed on I-405 in Southern California. With up to 10 detectors of different types under concurrent test in each of six lanes, a means for automating the testing process became imperative because traditional human verification methods were not practical. This paper describes an automated data acquisition and verification system that uses a consensus of the results from all detectors under test, along with those of a reference image processing system, to create a preliminary ground truth record requiring manual verification for only a small percentage of ambiguous cases. Individual detector performance is then assessed by comparison with this verified data set. The test bed architecture, data fusion methodology, computer vision methods, operator interface, and performance results are discussed.