Showing papers in "Transportation Research Record in 2000"

Simulation laboratory for evaluating dynamic traffic management systems

Abstract: Advanced traffic management systems (ATMS) and advanced traveler information systems (ATIS) are promising technologies for achieving efficiency in the operation of transportation systems. A simulation-based laboratory environment, MITSIMLab, is presented that is designed for testing and evaluation of dynamic traffic management systems. The core of MITSIMLab is a microscopic traffic simulator (MITSIM) and a traffic management simulator (TMS). MITSIM represents traffic flows in the network, and the TMS represents the traffic management system under evaluation. An important feature of MITSIMLab is its ability to model ATMS or ATIS that generate traffic controls and route guidance based on predicted traffic conditions. A graphical user interface allows visualization of the simulation, including animation of vehicle movements. An ATIS case study with a realistic network is also presented to demonstrate the functionality of MITSIMLab.

Day-to-Day Travel-Time Trends and Travel-Time Prediction from Loop-Detector Data:

Abstract: An approach is presented for estimating future travel times on a freeway using flow and occupancy data from single-loop detectors and historical travel-time information. Linear regression, with the stepwise-variable-selection method and more advanced tree-based methods, is used. The analysis considers forecasts ranging from a few minutes into the future up to an hour ahead. Leave-a-day-out cross-validation was used to evaluate the prediction errors without underestimation. The current traffic state proved to be a good predictor for the near future, up to 20 min, whereas historical data are more informative for longer-range predictions. Tree-based methods and linear regression both performed satisfactorily, showing slightly different qualitative behaviors for each condition examined in this analysis. Unlike preceding works that rely on simulation, real traffic data were used. Although the current implementation uses measured travel times from probe vehicles, the ultimate goal is an autonomous system that r...

Accident Prediction Models With and Without Trend: Application of the Generalized Estimating Equations Procedure

Abstract: Accident prediction models (APMs) are useful tools for estimating the expected number of accidents on entities such as intersections and road sections. These estimates typically are used in the identification of sites for possible safety treatment and in the evaluation of such treatments. An APM is, in essence, a mathematical equation that expresses the average accident frequency of a site as a function of traffic flow and other site characteristics. The reliability of an APM estimate is enhanced if the APM is based on data for as many years as possible, especially if data for those same years are used in the safety analysis of a site. With many years of data, however, it is necessary to account for the year-to-year variation, or trend, in accident counts because of the influence of factors that change every year. To capture this variation, the count for each year is treated as a separate observation. Unfortunately, the disaggregation of the data in this manner creates a temporal correlation that presents...

Energy-Derived, Damage-Based Failure Criterion for Fatigue Testing:

Abstract: Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied entirely on the arbitrary selection of a fixed criterion. The constant strain and constant stress modes of fatigue loading have been described by a consistent definition of failure in flexural fatigue testing because of the distinctly different application of energy during the loading history. The most widely accepted definition is a decrease in initial stiffness by 50 percent. Procedures examining energy input and dissipated energy have required different schemes for each mode in an attempt to describe similar states of damage in the mixture. A proposed method is presented for examining dissipated energy to select a consistent level of material behavior that is indicative of the damage accumulation in the mixture. This procedure shows the similarity between the constant stress and constant strain modes of testing and is shown to provide the potential for unifying the now phenomenological description of fatigue...

Utilization of Construction and Demolition Debris Under Traffic-Type Loading in Base and Subbase Applications

Abstract: As construction and remediation take place throughout New Jersey, the amount of construction and demolition debris increases, while the availability of landfill space decreases. A viable solution for disposing of these materials is to incorporate them into base and subbase applications. An extensive laboratory program was conducted on two types of construction and demolition debris: recycled concrete aggregate (RCA) and recycled asphalt pavement aggregate (RAP). These two materials were compared with dense-graded aggregate base coarse (DGABC), which currently is being used in roadway base applications in New Jersey. Both RCA and RAP were mixed at various percentages with the DGABC to evaluate whether an optimum mix blend could be formulated. The materials were evaluated under a traffic-type loading scheme that included resilient modulus and permanent deformation via cyclic triaxial testing. Laboratory tests indicated that the RAP, RCA, and DGABC blended materials all obtained higher resilient modulus values than the currently used DGABC. The permanent deformation results indicated that the RCA mixed samples obtained the lowest amount of permanent deformation when the material was cyclically loaded to 100,000 cycles. In contrast, the permanent deformation testing on RAP mixed samples resulted in the highest amount of permanent deformation at the same number of cycles. Existing models currently used for quarried base and subbase materials were used to predict the permanent deformation in the recycled materials. Laboratory test results indicated that these models could be used for predicting permanent deformation in unbound recycled materials.

Control Strategies for Transit Priority

Abstract: Control strategies for transit priority have long been recognized as having the potential to improve traffic performance for transit vehicles, which could also lead to improved schedule reliability, reduced operating costs, and greater ridership. However, there have been relatively few successful implementations of transit priority measures on urban networks with signalized intersections in coordinated signal systems. Existing control strategies are reviewed, the major factors affecting transit priority are identified, and the formulation of both passive and active transit priority strategies for arterials with coordinated traffic signals are described. The proposed strategies were evaluated on a real-life arterial corridor. The proposed passive and active priority strategies placed major emphasis on the systemwide improvements to the transit movements and on minimization of the adverse impacts to the rest of the traffic stream. The criteria used to grant priority include the availability of spare green t...

Conditional Bus Priority at Signalized Intersections: Better Service with Less Traffic Disruption

Abstract: Conditional priority for buses at signalized intersections means that late buses are given priority and early buses are not. This scheme is a method of operational control that improves service quality by keeping buses on schedule. A conditional bus priority implementation in Eindhoven, the Netherlands, is described. Results show the strong improvement in schedule adherence compared with a no-priority situation. Traffic impacts at an intersection were studied for three scenarios—no priority, absolute priority, and conditional priority. Compared with no priority, absolute priority increased delays significantly while conditional priority had almost no impact.

Content of variable message signs and on-line driver behavior

Abstract: Variable message signs (VMS) are programmable traffic control devices that convey nonpersonalized real-time information on network traffic conditions to drivers encountering them. Especially useful under incidents, VMS aim to influence driver routing decisions to enhance network performance. This study investigates the effect of different message contents on driver response under VMS. Presumably, if the message content is a significant factor in driver response, the traffic controller can use it as a control variable to influence network traffic conditions positively without compromising the integrity of information. This issue is addressed through an on-site stated preference user survey. Logit models are developed for drivers' diversion decisions. The analysis suggests that content in terms of the level of detail of relevant information significantly affects drivers' willingness to divert. Other significant factors include socioeconomic characteristics, network spatial knowledge, and confidence in the displayed information. Results also indicate differences in the response attitudes of semitrailer truck drivers compared to other travelers. They provide substantive insights for the design and operation of VMS-based information systems.

Distribution of strains within hot-mix asphalt binders: Applying imaging and finite-element techniques

Abstract: Because of several orders of magnitude difference between the stiffness of aggregate and binder and the randomness of the binder domain boundaries, the induced deformation under loading can result in a wide distribution of stresses and strains within each of the components. It is expected that although aggregates undergo small strains, most of the strain will accumulate within the binder. Although studies have covered the micromechanics of hot-mix asphalt (HMA), information about the actual typical distribution of asphalt binder domains in HMA and the resulting distribution of stresses and strains is scarce. In this study, advances in imaging techniques are applied to understand the distribution of binder and air voids in selected HMAs. The objective is to determine the strain distribution within the binder using digitized images analyzed with finite-element procedures. This approach captures the image of the specimen cross section and converts the image into finite-element mesh after image processing. The images are converted to finite-element mesh and the finite-element program ABAQUS provides numerical solutions to relate bulk stresses or strains applied to the asphalt mixture to stresses and strains within the binder domains. The results are presented including a summary of the distribution of directional binder film thickness and maximum strains in the mastic domain. Also included is a discussion of the effect of air voids and mineral fillers.

Requirements for Evaluating Traffic Signal Control Impacts on Energy and Emissions Based on Instantaneous Speed and Acceleration Measurements

Abstract: The evaluation of many transportation network improvements commonly is conducted by first estimating average speeds from a transportation or traffic model and then converting these average speeds into emission estimates based on an environmental model such as MOBILE Unfortunately, recent research has shown that certainly average speed and perhaps even simple estimates of the amount of delay and the number of stops on a link are insufficient measures to fully capture the impact of intelligent transportation system strategies such as traffic signal coordination In an attempt to address this limitation, the application of a series of multivariate fuel consumption and emission prediction models is illustrated, both within a traffic simulation model of a signalized arterial and directly to instantaneous speed and acceleration data from floating cars traveling down a similar signalized arterial The application of these multivariate relationships is illustrated for eight light-duty vehicles, ranging in size f

Comparison of VISSIM and CORSIM Traffic Simulation Models on a Congested Network

Abstract: Traffic simulation packages like CORSIM and VISSIM are frequently used as tools for the analysis of traffic since they are effective approaches for quantification of the benefits and limitations of different alternatives. The concern of those who are cautious or skeptical about the application of a complex program to making a critical design decision is often appropriate, as many models are unproven or little information about their accuracy is available. As these simulation models become easier to use, it may be practical to use more than one model in some studies. The two-model approach was applied as a means of making the analysis more reliable and the results more defensible. The results proved the consistency and reasonableness of the simulation tools and provided everyone involved with confidence about the analysis. The study also illustrated the value of using a range of performance measures and a sensitivity analysis. More generally, it proved the value of providing as much comparative information as possible before making a design decision. The results were generally consistent, and the end product was a set of clear, defensible, and well-supported conclusions. Although the experience gained through the application of CORSIM and VISSIM was in some ways unique to the study area, this experience can provide insight to other transportation professionals charged with selecting and applying these simulation models to similar networks. To that end, some of the characteristics of both models are contrasted.

Effects of fiber reinforcement on strength and volume change in expansive soils

Abstract: The results of a research study to investigate the influence of discrete and randomly oriented polypropylene fiber reinforcement on expansive soil stabilization are presented. Two expansive soils were used as control soils in the testing program. Two types of fibers and four fiber dosages (0,0.3,0.6, and 0.9 percent by dry weight of soil) were considered. Both raw and fiber-reinforced clayey samples were prepared and subjected to unconfined compressive strength (UCS), volumetric shrinkage, three-dimensional free swell, and swell pressure tests. Test results were statistically analyzed to investigate the effectiveness of fiber reinforcement on strength, swell, and shrinkage characteristics of expansive clays. Results indicated that the fiber reinforcement enhanced the UCS of the soil and reduced both volumetric shrinkage strains and swell pressures of the expansive clays. The fiber treatment also increased the free swell potential of the soils. Practical implications of the findings and future research dir...

Effects of transportation infrastructure and location on residential real estate values: application of spatial autoregressive techniques

Abstract: Proximity to transportation infrastructure (highways and public transit) influences residential real estate values. Housing values also are influenced by propinquity to a shopping facility or a recreational amenity. Spatial autoregressive (SAR) models were used to estimate the impact of locational elements on the price of residential properties sold during 1995 in the Greater Toronto Area. A large data set consisting of 27,400 freehold sales was used in the study. Moran's I was estimated to determine the effects of spatial autocorrelation that existed in housing values. SAR models, using a combination of locational influences, neighborhood characteristics, and structural attributes, explained 83 percent variance in housing values. Using the "comparable sales approach," a spatiotemporal lag variable was estimated for every property in the database. This research discovered that SAR models offered a better fit than nonspatial models. This study also discovered that in the presence of other explanatory varia...

Gas-Kinetic Modeling and Simulation of Pedestrian Flows

Abstract: Insight into pedestrian flow operations is important in both planning and geometric design of infrastructure facilities such as railway stations as well as in the management of pedestrian flows in such facilities. Lack of empirical knowledge regarding the characteristics of pedestrian flows under varying circumstances and designs motivates using a model-based approach. In this study, a new pedestrian flow model based on the gaskinetic modeling paradigm is established. The mesoscopic equations describe the dynamics of so-called pedestrian phase-space density, which can be considered as a two-dimensional generalization of the phase-space density used in gas-kinetic vehicular traffic flow. Convection, acceleration, and noncontinuum transition terms govern the dynamics. The latter terms reflect the dynamic influence of pedestrians decelerating and the changing angle of movement due to pedestrians interacting. Numerical solutions of the resulting gas-kinetic equations are established by using a novel particle ...

Modeling Inertia and Compliance Mechanisms in Route Choice Behavior Under Real-Time Information:

Abstract: This research examines route choice, in the presence of real-time information, as a consequence of two underlying behavioral mechanisms: compliance and inertia. The compliance mechanism reflects the propensity of a user to comply with the information supplied by advanced traveler information systems (ATIS). The inertial mechanism represents the tendency of users to continue on their current paths. These two mechanisms in route choice are neither mutually exclusive nor collectively exhaustive. A framework is proposed to model these mechanisms explicitly. The proposed framework decomposes the route choice into two states by exploiting the user's path choice structure (resulting from the current choice prior to the decision of interest) and the information supplied by ATIS. In each state, the mechanisms are incorporated by associating their utilities with those that reflect the specific attributes of the alternative paths. The resulting nested choice structure is implemented using the multinomial probit model. This framework is illustrated using route choice data obtained from dynamic interactive simulator experiments. The empirical results strongly support the simultaneous presence of both the compliance and inertia mechanisms in route choice behavior. The results also indicate that information quality, network loading and day-to-day evolution, level-of-service measures, and trip-makers' prior experience are significant determinants of route choice through the inertial and compliance mechanisms. These findings have important implications in travel behavior forecasting, ATIS design and evaluation, demand management, and network state prediction.

Albatross: multiagent, rule-based model of activity pattern decisions

Abstract: The development of ALBATROSS: A Learning-Based, Transportation-Oriented Simulation System is summarized. This activity-based model of activity-travel behavior is derived from theories of choice heuristics that consumers apply when making decisions in complex environments. The model, one of the most comprehensive of its kind, predicts which activities are conducted when, where, for how long, and with whom, and the transport mode involved. In addition, various logical, temporal, spatial, spatial-temporal, and institutional constraints are incorporated in the model. The conceptual underpinnings of the model, its architecture, the functionality of its key agents, data collection, and model performance are discussed.

Optimal Bus Stop Spacing Through Dynamic Programming and Geographic Modeling

Abstract: A discrete approach was used to model the impacts of changing bus-stop spacing on a bus route. Among the impacts were delays to through riders, increased operating cost because of stopping delays, and shorter walking times perpendicular to the route. Every intersection along the route was treated as a candidate stop location. A simple geographic model was used to distribute the demand observed at existing stops to cross-streets and parallel streets in the route service area, resulting in a demand distribution that included concentrated and distributed demands. An efficient, dynamic programming algorithm was used to determine the optimal bus-stop locations. The model was compared with the continuum approach used in previous studies. A bus route in Boston was modeled, in which the optimal solution was an average stop spacing of 400 m (4 stops/mi), in sharp contrast to the existing average spacing of 200 m (8 stops/mi). The model may also be used to evaluate the impacts of adding, removing, or relocating selected stops.

Determining the number of probe vehicles for freeway travel time estimation by microscopic simulation

Abstract: Using probe vehicles to collect real-time traffic information is considered an efficient method in real-world applications. How to determine the minimum number of probe vehicles required for accurate estimate of link travel time is a question of increasing interest. Although it usually is assumed that link travel time is normally distributed, it is shown, on the basis of simulation results, that sometimes this is not true. A heuristic of determining the minimum number of probe vehicles required is developed to accommodate this situation. In addition, the impact of traffic volume on the required probe vehicle number is discussed.

Enhanced genetic algorithm for signal-timing optimization of oversaturated intersections

Abstract: Enhancements were provided to a previously developed genetic algorithm (GA) for traffic signal optimization for oversaturated traffic conditions. A broader range of optimization strategies was provided to include modified delay minimization with a penalty function and throughput maximization. These were added to the initial delay minimization strategy and were further extended to cover all operating conditions. The enhanced program was evaluated at different intersection spacings. The optimization strategies were evaluated and compared with their counterpart from TRANSYT-7F, version 8.1. A microscopic stochastic simulation program, CORSIM, was used as the unbiased evaluator. Hypothesis testing indicated that the GA-based program with average delay minimization produced a superior signal-timing plan compared with those produced by other GA strategies and the TRANSYT-7F program in terms of queue time. It was also found from the experiments that TRANSYT-7F tended to select longer cycle lengths than the GA program to reduce random plus oversaturation delay.

Global Positioning System as Data Collection Method for Travel Research

Abstract: The technology of Global Positioning Systems (GPS) provides new ways for collecting information about travel behavior. When it is used in combination with an electronic travel diary, valuable information of high quality about travel behavior becomes available. To learn about the possibilities of this new technology, a pilot study involving 151 people was performed in the Netherlands. What makes this pilot unique is the monitoring of all modes of travel, not just travel by motorized vehicles. The findings suggest that although it is possible to monitor all travel modes, data quality differs among them. The GPS device registered nearly all car driver trips, compared to half of the tram and train trips. When trips are registered, public transport trips are registered with a higher accuracy level than car trips. For specific trips, respondents did not use the equipment because of the burden placed on them or because of a lack of time. This was especially the case for walking, cycling, public transport, shoppi...

Development and Evaluation of Intelligent Bus Priority Concept

Abstract: Development and laboratory testing of an intelligent concept for providing priority to buses at signalized intersections without disrupting progression are discussed. The concept used bus position information to predict when in the cycle a bus would arrive at the bus stop and stop line of a signalized intersection and to determine whether a bus needs priority. The strategy used to provide priority was selected on the basis of the estimated arrival time of the bus at the stop line. Priority was provided by using phase extension, phase insertion, and early return strategies without causing the controller to drop from coordination. Implementation of the strategies was accomplished through normal traffic-signal controller commands (such as Ring Force Offs and Phase Holds). Hardware-in-the-loop simulation studies were performed to evaluate the effectiveness of the concept with real traffic-signal controllers. The performance of the intelligent bus priority approach was examined at three volume-to-capacity leve...

Effect of speed, flow, and geometric characteristics on crash frequency for two-lane highways

Abstract: Although during the past several years significant progress has been made in improving safety on U.S. highways, the frequency and severity of crashes continue to be of concern. A better understanding of the factors associated with crashes will facilitate the identification of suitable countermeasures that could further reduce the occurrence of crashes. Results are presented from a study that determines how the characteristics of speed, flow, and geometry affect the crash rates for two-lane highways. Deterministic models that relate the crash rate with the mean speed, standard deviation of speed, flow per lane, lane width, and shoulder width are presented. The multivariate ratio of polynomials method was used to develop the models. Research was limited to two-lane roadways in Virginia with speed limits of 89 km/h (55 mph). The data were obtained from speed-monitoring stations established by the Virginia Department of Transportation and from police accident reports from January 1993 to September 1995.

Evaluating Carsharing Benefits

Abstract: Carsharing is an automobile rental service intended to substitute for private vehicle ownership. Carsharing emphasizes affordability and convenience. Vehicles are rented by the hour, located near residences, and require minimal effort to check in and out. Carsharing services are common in some European countries and are increasing in North America. Carsharing gives consumers a practical alternative to owning a personal vehicle that is driven less than about 6,000 miles (10,000 kilometres) per year. Carsharing has lower fixed costs and higher variable costs than private vehicle ownership. This price structure makes occasional use of a vehicle affordable, even to low-income households. It also gives drivers an incentive to minimize their vehicle use and rely on other travel options as much as possible. Carsharing typically reduces average vehicle use by 40-60% among drivers who rely on it, making it an important transportation demand management strategy. Despite these benefits, carsharing is growing slowly and will need to overcome several barriers to achieve its full potential.

Predicting Operating Speeds on Tangent Sections of Two-Lane Rural Highways:

Abstract: Prediction and estimation of speeds on two-lane rural highways are of enormous significance to planners and designers. Estimation of speeds on curves may be easier than prediction of speeds on tangent sections because of the strong correlation of speeds with a few defined and limiting variables, such as curvature, superelevation, and the side-friction coefficients between road surface and tires. On tangent sections, however, the speed of vehicles is dependent on a wide array of roadway characteristics, such as the length of the tangent section, the radius of the curve before and after the section, cross-section elements, vertical alignment, general terrain, and available sight distance. Few studies have dealt with this issue because a considerable database is necessary to identify any significant trends and substantial modeling effort is required. Research analyzed the variability of the operating speeds on 162 tangent sections of two-lane rural highways, and models were developed for prediction of operat...

Customer Satisfaction Among Transit Riders: How Customers Rank the Relative Importance of Various Service Attributes

Abstract: One of the reasons transit organizations collect customer-satisfaction information is to help set priorities for service improvements. Customer-satisfaction survey results can help managers choose from among a long list of service attributes (e.g., vehicle cleanliness or on-time performance) to more optimally focus their organization's attention and resources. To make these choices, managers need to know how important each service characteristic is to their customers. Common techniques for gauging the relative importance of various service characteristics to transit customers are examined. Empirical data from the Bay Area Rapid Transit District are used to compare and contrast several of these techniques. The analysis suggests that a relatively simple approach using a ranking of bivariate correlation coefficients from high to low may be the most advantageous technique for ranking the relative importance of transit attributes from a customer perspective.

Simulation model for calculating pavement temperatures including maximum temperature

Abstract: A simulation model has been developed to calculate the temperatures of asphalt concrete during summer. Input data to the simulation model are hourly values for solar radiation, air temperature, and wind velocity. Longwave radiation incident to and outgoing from the pavement surface is calculated from the air and pavement surface temperatures, respectively. The portion of the incident shortwave radiation absorbed by the pavement surface is calculated from the albedo of the surface. By means of a finite difference approximation of the heat transfer equation, the temperatures are calculated under the surface. Apart from radiation and heat transfer, convection losses from the pavement surface are also calculated depending on wind velocity, air temperature, and surface temperature. The formulas used for the calculation of radiation and the simulation model as a whole are validated by comparison with measurements, showing good agreement. A method for the calculation of direct solar radiation from a clear sky, a...

Low-Temperature Fracture Testing of Asphalt Binders: Regular and Modified Systems

Abstract: The results of low-temperature fracture testing of a large number of both regular and modified asphalt binders are discussed. Two Strategic Highway Research Program (SHRP) binders (Materials Reference Library Codes AAG-2 and AAN) were evaluated with 5 percent by weight of a variety of commonly used polymer modifiers. Specimens of three different sizes were tested in a three-point bend configuration, both with and without a notch. The original SHRP effort was aware of the need for a rigorous fracture mechanics-type binder test, but because of a lack of time and resources, only the bending beam rheometer and the direct tension test were ultimately developed. Some of the differences between failure strain and fracture toughness measurements are discussed, as well as how these differences may relate to pavement performance. The results of this study demonstrate that there is a large range of notch sensitivities and fracture energies for different polymer-modified binders, suggesting that the ductile-to-brittl...

Developing a Dynamic Traffic Management Modeling Framework for Hurricane Evacuation

Abstract: Evacuation is becoming increasingly difficult as the population of hurricane-prone regions continues to grow dramatically. In addition, development in coastal communities in the United States is expected to continue to greatly outpace new construction and improvements to the highway infrastructure. Consequently, there is a great need for hurricane evacuation models, which allow emergency response personnel to develop effective evacuation plans and management strategies. The development of a dynamic hurricane evacuation modeling framework is described, which can be used for long-term and short-term planning purposes as well as for real-time operational purposes.

Top-Down Cracking in Washington State Asphalt Concrete Wearing Courses

Abstract: For years, pavement engineers within the Washington State Department of Transportation (WSDOT) have observed that longitudinal and fatigue (multiple-interconnected) cracks in their thicker asphalt concrete (AC) pavements appeared to crack from the top of the wearing course downward. Often, the cracks stop at the interface between the wearing course and the underlying bituminous layers (a depth of about 50 mm). Studies done elsewhere in the United States and internationally have reported similar results. The results of extensive coring that WSDOT routinely collects in its pavement rehabilitation process were compared in a study. WSDOT normally cores AC pavements to determine thickness for use in mechanistic-empirical design. In addition to coring for AC thickness, specific information noting surface-initiated (top-down) cracking with the crack depth or full-depth cracking was noted. WSDOT observed top-down cracking occurring in the thicker sections, with thinner sections cracking full depth. Top-down cracking generally started within 3 to 8 years of paving for pavement sections that were structurally adequate and were designed for adequate equivalent single-axle loads.

Incorporating Road Safety into Pavement Management

Abstract: Improving road safety through proper pavement engineering and maintenance should be one of the major objectives of pavement management systems. When pavements are evaluated in terms of safety, a number of factors related to pavement engineering properties are raised, such as pavement geometric design, paving materials and mix design, pavement surface properties, shoulder type, and pavement color and visibility. Each year there are voluminous annual reports on traffic accident statistics and discussions of such road safety issues as road safety modeling and pavement safety measurements and criteria. Although road safety may be considered a separate area, it should be incorporated into pavement management systems. The main pavement engineering relationships associated with road safety are identified, and the various aspects of road safety related to pavement management, such as pavement types, pavement surface macrotexture and microtexture, and pavement safety measurements, criteria, and evaluation methods, are discussed. A systematic approach is proposed for the coordination of pavement maintenance programs with road safety improvement and the incorporation or integration of safety management with pavement and other management systems. Finally, a list of possible remedial measures for road safety improvements associated with pavement maintenance activities is recommended.