Showing papers in "Journal of Transportation Engineering-asce in 2014"

How to evacuate: model for understanding the routing strategies during hurricane evacuation

Abstract: This paper explains a modeling approach that offers better understanding of the routing strategies taken by evacuees to reach a safe destination during hurricane evacuation. Route choice during evacuation is a complex process because evacuees may prefer to take the usual or familiar route on the way to the destination, or they might follow the routes recommended by the emergency officials. Depending on the condition of the traffic stream, sometimes they might switch to a different route to obtain better travel time from the one initially attempted, i.e., the routing behavior is random. By using data from Hurricane Ivan, a mixed (random parameters) logit model is estimated which captures the decision making process on what type of route to select while accounting for the existence of unobserved heterogeneity across households. Estimation findings indicate that the choices of evacuation routing strategy involve a complex interaction of variables related to household location, evacuation characteristics, and socioeconomic characteristics. The findings of this study are useful to determine the manner in which different factions of people select a type of route for a given sociodemographic profile during an evacuation. Language: en

Development of a Data-Driven Platform for Transit Performance Measures Using Smart Card and GPS Data

Abstract: To improve customer satisfaction and reduce operation costs, transit authorities have been striving to monitor transit service quality and identify the key factors to enhance it. The recent advent of passive data collection technologies, e.g., automated fare collection (AFC) and automated vehicle location (AVL), has shifted a data-poor environment to a data-rich environment and offered opportunities for transit agencies to conduct comprehensive transit system performance measures. However, most AFC and AVL systems are not designed for transit performance measures, implying that additional data processing and visualization procedures are needed to improve both data usability and accessibility. This study attempts to develop a data-driven platform for online transit performance monitoring. The primary data sources come from the AFC and AVL systems in Beijing, where a passenger’s boarding stop (origin) and alighting stop (destination) on a flat-rate bus are not recorded. The individual transit rider’...

Application of Geographically Weighted Regression Technique in Spatial Analysis of Fatal and Injury Crashes

Abstract: Generalized linear models (GLMs) are the most widely used models utilized in crash prediction studies. These models illustrate the relationships between the dependent and explanatory variables by estimating fixed global estimates. Since crash occurrences are often spatially heterogeneous and are affected by many spatial variables, the existence of spatial correlation in the data is examined by means of calculating Moran’s I measures for dependent and explanatory variables. The results indicate the necessity of considering spatial correlation when developing crash prediction models. The main objective of this research is to develop different zonal crash prediction models (ZCPMs) within the geographically weighted generalized linear model (GWGLM) framework in order to explore the spatial variations in association between number of injury crashes (NOICs) (including fatal, severely, and slightly injured crashes) and other explanatory variables. Different exposure, network, and sociodemographic variabl...

Roughness Progression Model for Asphalt Pavements Using Long-Term Pavement Performance Data

Abstract: A reliable pavement performance prediction model is needed for road infrastructure asset management systems or pavement management systems. In this study, the data on roughness progression of asphalt pavements in the long-term pavement performance (LTPP) database was analyzed in order to develop such a model. The international roughness index (IRI) is a reasonable measure of the ride comfort perceived by occupants of passenger cars and hence used as the basis for the pavement performance prediction model developed in this research. A quantitative relationship between roughness progression and accumulative traffic load, structural number, annual precipitation, and freezing index was developed and validated. Five pavement performance levels were developed to express the extent of asphalt pavement deterioration. This is coupled with a reliability analysis based on the Weibull model to estimate the remaining service life of asphalt pavements. Effective treatments of pavements at the project level for ...

Improved k-nn for Short-Term Traffic Forecasting Using Temporal and Spatial Information

Abstract: This paper proposes an improved k-nearest neighbor (k-nn) model for short-term traffic forecasting and examines its applicability to forecasting for different links and time periods. The traditional k-nn model is adapted by formulating the weighted distance metric and the state vector, which consider both the temporal and spatial information. The adapted model’s performance is examined in a numerical test where the data are derived from global positioning system (GPS) devices in 180 taxis running in Guiyang, China. The test results demonstrate that the model that considers both the temporal and spatial information outperforms models that only consider temporal information and that adaptation of distance metrics could significantly improve the forecasting accuracy. The adapted model shows the promising performance in comparison with the historical average (HA) model and the artificial neural network (ANN) model. The test results also indicate that information from the upstream and the downstream li...

Robust Method for Automated Segmentation of Frames with/without Distress from Road Surface Video Clips

Abstract: Automated processing of road surface video clips captured for road condition assessment is necessary to detect the existence of road surface distress in less time and efforts. This paper presents a robust method for automated segmentation of frames with/without distress from road surface video clips captured by existing camera based imaging systems without any artificial lighting systems. The proposed method is based on an adaptive thresholding technique and user defined decision logic for automated detection of road surface distresses out of such video clips. This method has been implemented in a Windows Vista environment with the help of Visual Studio 2008 and OpenCV library and tested on 31 road surface video clips of Indian Highways. The results show that this method can segment a road surface video clip automatically into two categories of video frames, namely frames with distress and frames without distress, with accuracy up to 96% while saving a considerable amount of time and manpower resources.

Microscopic Estimation of Arterial Vehicle Positions in a Low-Penetration-Rate Connected Vehicle Environment

Abstract: Wireless communication among vehicles and roadside infrastructure, known as connected vehicles, is expected to provide higher-resolution real-time vehicle data, which will allow more effective traffic monitoring and control. Availability of connected vehicle technology among the vehicle fleet will likely grow gradually, but it will possibly remain limited, with many drivers potentially being unwilling to transmit their locations. This is problematic given that research has indicated that the effectiveness of many connected vehicle mobility applications will depend on the availability of location data from a minimum of 20–30% of roadway vehicles. In an effort to improve the performance of connected vehicle applications at low connected vehicle technology penetration rates, the authors propose a novel technique to estimate the positions of noncommunicating (unequipped) vehicles based on the behaviors of communicating (equipped) vehicles along a signalized arterial. Unequipped vehicle positions are e...

Mining the Characteristics of Secondary Crashes on Highways

Abstract: The prevention of secondary crashes is a high priority task in traffic incident management. However, the limited knowledge regarding the nature of secondary crashes largely impeded the development of established countermeasures. The primary goal of this paper is to improve the literature’s understanding of secondary crashes. This goal is achieved in two steps: first, with an analysis framework that accurately identifies secondary crashes by integrating rich traffic-sensor data with statewide-crash data and, second, by carefully investigating the characteristics of these identified secondary crashes. To that end, secondary crashes within a 27-mile section of a major highway in New Jersey were mined using the developed analysis framework, and a thorough examination of their characteristics has been performed. Empirical findings on the frequency of secondary crashes, their spatio-temporal distributions, clearance time, crash type, severity, and major contributing factors have been highlighted. Taken together, these preliminary results could potentially help transportation agencies make more informed decisions on mitigating secondary crashes and improve their incident management operations. To complement the results, further in-depth investigations using more high-resolution sensor data and high-quality incident records are suggested.

Optimization Framework for Bicycle Network Design

Abstract: This paper presents a new formulation for the network design problem as it relates to retrofitting existing roadway infrastructure for bicycles. The goal of the problem is, for a minimum cost, to connect all origin-destination pairs with paths where each roadway segment and intersection meets or exceeds a lower bound on its bicycling level of service. The length of each optimal path is constrained to be no greater than a given upper bound, which is expressed as a function of shortest path length. Experimental analysis on the Austin, Texas downtown region shows that a systems approach will yield different results than an approach that separately considers connecting each pair of origins and destinations, and that placing an upper bound on the amount of deviation from the shortest path will impact the design decisions. Model parameters, although the defaults are based on existing research, should be calibrated based on local data. Variants on the formulation are provided that allow for a trade-off between optimality and computational efficiency.

Impact of Abandoned and Disabled Vehicles on Freeway Incident Duration

Abstract: It is common to find a vehicle left on the shoulder, median, gore area, or on the travel lane for certain period of time. Experience from the state of Tennessee has shown that 78% of the freeway traffic-related incidents are attributable to disabled and abandoned vehicles. It is hypothesized that the longer the vehicle is left unattended within the right of way, the higher the probability of new incidents and secondary crashes. This paper utilized 2004–2010 freeway incident data in Tennessee to evaluate the effect of the length of incident durations caused by disabled and abandoned vehicles. Analysis evaluated the effect of these incidents with respect to roadway location, queue lengths, weather conditions, towing times, lane closure, and the source of incident notification. Temporal factors, including the spectra of the time of the day, the day of the week, and the seasons of the year were evaluated with respect to the number of incidents and incident durations. More disabled and abandoned vehicl...

Methods for Defining Spatiotemporal Influence Areas and Secondary Incident Detection in Freeways

Abstract: The likelihood of the occurrence of secondary incidents is usually linked to primary incidents by using predefined spatial and temporal criteria. This paper extends past research on secondary incident detection by defining the dynamic thresholds of the influence area of a primary incident, using detailed freeway traffic data from upstream loop detectors. The dynamic thresholds are defined by using both analytical and empirical approaches. Results that use analytical approaches to track the spatiotemporal boundaries of the influence upstream of a primary incident offer influence curves of different characteristics (influence duration and maximum spatial extent) with respect to the prevailing traffic conditions. To accurately detect secondary incidents, an empirical method based on spatiotemporal speed evolution is applied that imprints influence areas with respect to their dissipation patterns. The results of the proposed approach are compared to those of five commonly used static and dynamic methods for detecting secondary incidents. Their differences are identified and discussed. Language: en

Potentialities of Data-Driven Nonparametric Regression in Urban Signalized Traffic Flow Forecasting

Abstract: Single-interval forecasting of traffic variables plays a key role in modern intelligent transportation systems (ITSs). Despite the achievements of advanced ITS forecasting in literature, forecast modeling of urban signalized traffic flow, which shows rapid-intensive fluctuations associated with the nonlinear and nonstationary behavior of temporal evolution, is still one of its big challenges. From the perspective of field experts, the mathematical complexity of an advanced model is also a renewal obstacle in practice. On the other hand, the accessibility of large volumes of historical data and the concurrent advanced data management systems used to access them provide data-driven nonparametric regression with a renewal opportunity in practice. In order to address these problems effectively, this paper proposes a k nearest neighbor nonparametric regression (KNN-NPR) forecasting methodology to be tested against vast quantities of real traffic volume data collected from urban signalized arterials. Th...

Performance Characterization of Hot In-Place Recycled Asphalt Mixtures

Abstract: Despite the widespread use of in-place recycling, limited information is available in the literature on in situ and laboratory properties of materials placed through in-place recycling. The main objectives of present study were to investigate the in situ recycled material characteristic that includes the potential of asphalt mixtures for permanent deformation, fatigue cracking, and low-temperature cracking, and the effect of a special technique of hot in-place recycling and rejuvenation on asphalt binder rheological properties. To accomplish these objectives, a two-phase experimental program was designed to determine the performance-related parameters of 100% in-place recycled mixtures using one of the in-place recycling techniques in which overlay is not needed. The experimental program included the measurement of mixtures’ mechanical properties and binder rheological properties. The present study revealed that the stiffness of the asphalt mixtures after recycling had increased compared to that b...

Passenger Car Units at Different Levels of Service for Capacity Analysis of Multilane Interurban Highways in India

Abstract: Passenger car units (PCU) of different types of vehicles are required to convert a mixed traffic stream into a homogeneous equivalent, and thereby to express the mixed traffic flow in terms of equivalent number of passenger cars. Earlier studies have reported that PCU for a vehicle is dynamic in nature and changes with traffic volume and proportional share of a vehicle type in the traffic stream. The present study provides PCU values for different types of vehicles typically found on interurban multilane highways in India at different levels of service (LOS). Traffic simulation model VISSIM is used to generate the traffic flow and speed data for conditions that are difficult to obtain from field observations. Important VISSIM parameters are first calibrated to reflect mixed traffic flow behavior and then the software is used to draw the speed-volume relationships for cars and one of the remaining four categories of vehicles in the traffic stream. The proportion of second category of the vehicle was also varied to observe its effects on PCU values. Finally, PCU values are suggested for different type of vehicles at different LOS and for different traffic composition on four-lane and six-lane divided highways.

Rail Transit Route Optimization Model for Rail Infrastructure Planning and Design: Case Study of Saint Andrews, Scotland

Abstract: This paper is aimed at developing a rail transit route optimization model (RTROM) for cost-effective and sustainable rail infrastructure planning and design. Locations of rail transit routes and stations depend on many factors, including potential ridership, costs of land, construction and operation, land use, connecting routes, passenger travel times, and environmental impacts. Suitably located rail transit routes effectively serve the potential demand while also minimizing costs and environmental impacts. Thus, a common problem in all rail infrastructure planning and design projects is to identify the best possible route that satisfies design constraints (such as minimum radius, maximum gradient, and vertical clearance), geographical considerations (such as demand generators and socio-economically sensitive areas) and objectives (such as minimization of associated costs and environmental impacts, or maximization of net benefits). The developed RTROM uses a genetic algorithm for performing optimization, which is integrated to a geographic information system for seamless transfer of land-use, environmental, and topographic data during the optimal search process. The model is tested in a real-world case study from Saint Andrews, Scotland. The lessons learned from the real-world application of the model are discussed. Many extensions of the model remain to be tested in future works.

Optimization of ultrasonic rail-defect inspection for improving railway transportation safety and efficiency

Abstract: Broken rails are the most frequent cause of freight-train derailments in the United States. Consequently, reducing their occurrence is a high priority for the rail industry and the U.S. Federal Railroad Administration. Current practice is to periodically inspect rails to detect defects using nondestructive technology such as ultrasonic inspection. Determining the optimal rail inspection frequency is critical to efficient use of infrastructure management resources and maximizing the beneficial impact on safety. Minimization of derailment risk, costs of inspection vehicle operation, rail defect repair, and corresponding train delay are all affected by rail inspection frequency. However, no prior research has incorporated all of these factors into a single integrated framework. The objective of this paper is to develop an analytical model to address the trade-offs among various factors related to rail defect inspection frequency, so as to maximize railroad safety and efficiency. The analysis shows that the optimal inspection frequency will vary with traffic density, rail age, inspection technology reliability, and other factors. The optimization model provides a tool that can be used to aid development of better-informed, more effective infrastructure management and accident prevention policies and practices.

Assessment of Winter Maintenance of Porous Asphalt and Its Function for Chloride Source Control

Abstract: This study presents the findings from research conducted at the University of New Hampshire Stormwater Center (UNHSC) which investigated porous pavements as a potential strategy for minimizing the use of deicing chemicals for winter maintenance. In cold regions, chloride is an integral component of winter maintenance and safe usage of transportation surfaces. Chloride-laden runoff from impervious surfaces threatens aquatic habitats, degrades drinking water supplies, and corrodes infrastructure. State and federal environmental agencies are beginning to regulate chloride usage through the implementation of total maximum daily loads (TMDLs). Parking surfaces in some watershed studies have been shown to be the single largest chloride source in storm-water runoff, in some instances contributing up to 50% of the total load. This study examined winter maintenance over two winters and 38 storms from 2006–2008. The study evaluated winter performance in response to deicing practices by measuring skid resist...

Development of a Signal Optimization Model for Diverging Diamond Interchange

Abstract: As one of the most popular unconventional interchange designs, diverging diamond intersection (DDI) has received increased attention over the past decade. Through a reverse operation of traffic movements between its two crossover intersections, DDI can accommodate more traffic movements within each phase. To design an effective signal plan for DDIs, one needs to address the following two critical issues: (1) how to select the common cycle length and green splits at each crossover intersection under different geometric conditions, and (2) how to coordinate a DDI’s two crossover intersections with its adjacent conventional intersections. To contend with these issues, this paper presents an optimization model with the objective of maximizing intersection capacity to yield the optimal green splits and cycle length. Also, in view of the potentially large left-turn traffic volumes from the freeway off-ramps, this study has further modified a model to provide progressions to both left-turn and through tr...

Methodology to Characterize Ideal Short-Term Counting Conditions and Improve AADT Estimation Accuracy Using a Regression-Based Correcting Function

Abstract: Transportation agencies’ motor vehicle count programs tend to be well established and robust with clear guidelines to collect short-term count data, to analyze data, develop annual average daily traffic (AADT) adjustment factors, and to estimate AADT volumes. In contrast, bicycle and pedestrian traffic monitoring is an area of work for most transportation agencies. In most agencies, there are a low numbers of counting sites and limited agency experience to manage a city-wide or state-wide system of collecting, processing, and using nonmotorized data. Short duration counts are used to estimate longer duration volumes such as AADT. Because bicycle or pedestrian short-term counts vary dramatically over time and significantly more than motorized vehicle counts, the direct application of motorized vehicle AADT estimation methods may be inadequate. The goal of this paper is to present a methodology that will enhance, if needed, existing AADT estimation methods widely employed for motorized vehicle counts. The proposed methodology is based on the analysis of AADT estimation errors using regression models to estimate a correcting function that accounts for weather and activity factors. The methodology can be applied to any type of traffic with high volume variability but in this research is applied to a permanent bicycle counting station in Portland, Oregon. The results indicate that the proposed methodology is simple and useful for finding ideal short-term counting conditions and improving AADT estimation accuracy.

Calibrating Road Design Guides Using Risk-Based Reliability Analysis

Abstract: Existing geometric design guides provide deterministic design criteria for highway elements that ignore the uncertainty associated with many design parameters. Reliability analysis has been advocated as an approach to account for this uncertainty and to evaluate the risk associated with a particular design feature. This paper discusses one important application of reliability analysis: the calibration of geometric design models to yield consistent safety (risk) levels. The paper provides calibrated design charts for the middle ordinate M, defined as the lateral distance between edge of median barriers and centerline of the adjacent traffic lane, at different probability of noncompliance levels. The results show that the calibrated values of M are generally lower than those derived from the AASHTO design guide. The calibrated design charts can offer designers dealing with highways with constricted right-of-way an option to use lower middle ordinate values and enable them to estimate the safety consequences of their decisions. Overall, the calibrated charts can aid the decision maker in determining the safety implications of deviating from geometric design standards and quantifying the safety level built in design values that are deemed acceptable.

Optimization of Speed Hump Profiles Based on Vehicle Dynamic Performance Modeling

Abstract: Speed humps are in widespread use around the world. Despite their effective performance in increasing safety, they cause considerable damage to vehicles and discomfort to drivers and passengers. This paper investigates the dynamic response of vehicles on different types of speed humps using a multibody simulation software package that is popular in the automotive industry. Following this evaluation, two new profiles are recommended to optimize the dynamic performance of speed humps. A series of formulas are also presented to estimate the dynamic performance of passenger cars on flat-topped and parabolic humps based on vehicle speed, hump dimensions, and driving behavior while traversing the hump. The results show that, for flat-topped humps, the ramp length (or entrance slope) has the greatest effect on vehicle performance. It is found that the dynamic performance of the recommended profiles is much better than that of conventional humps.

New Methodology for Intersection Signal Timing Optimization to Simultaneously Minimize Vehicle and Pedestrian Delays

Abstract: This study introduces a new methodology for signal timing optimization that is carried out by adjusting green splits of a.m. peak, p.m. peak, and rest of the day timing plans for each signalized intersection in the urban street network without changing the existing cycle length and signal coordination to minimize total vehicle and pedestrian delays per cycle. It contains a basic model that handles vehicle delays only and an enhanced model that simultaneously addresses vehicle and pedestrian delays using two different pedestrian delay estimation methods. Both models are incorporated into a high fidelity simulation-based regional travel demand forecasting model for detailed traffic assignments. A computational study is performed for methodology application using data on Chicago metropolitan area travel demand, traffic counts, geometric designs, and signal timing plans for major intersections in the Chicago central business district (CBD) area. A sensitivity analysis is conducted in the application of the enhanced model to examine the impacts of assigning different weights to vehicle and pedestrian delays on intersection vehicle travel time and delay reductions after signal timing optimization. The computational experiment reveals that after systemwide signal timing optimization, vehicle delays in the CBD area could reduce by 13% when considering only vehicle delays and by 5% when simultaneously considering vehicle and pedestrian delays.

Modeling Seasonal Heteroscedasticity in Vehicular Traffic Condition Series Using a Seasonal Adjustment Approach

Abstract: Heteroscedasticity modeling in transportation engineering is primarily conducted in short-term traffic condition forecasting to generate time varying prediction intervals around the point forecasts through quantitatively predicting the conditional variance of traffic condition series. Until recently, the generalized autoregressive conditional heteroscedasticity (GARCH) model and the stochastic volatility model have been two major approaches adopted from the field of financial time series analysis for traffic heteroscedasticity modeling. In this paper, recognizing the pronounced seasonal pattern in traffic condition data, a simple seasonal adjustment approach is explored for modeling seasonal heteroscedasticity in traffic-flow series, and four types of seasonal adjustment factors are proposed with respect to daily or weekly patterns. Using real-world traffic-flow data collected from highway systems in the United Kingdom and the United States, the proposed seasonal adjustment approach is implemented...

Calibration of Pavement ME Design and Mechanistic-Empirical Pavement Design Guide Performance Prediction Models for Iowa Pavement Systems

Abstract: The AASHTO mechanistic-empirical pavement design guide (MEPDG) pavement performance models and the associated AASHTOWare pavement ME design software are nationally calibrated using design inputs and distress data largely from the national long-term pavement performance (LTPP). Further calibration and validation studies are necessary for local highway agencies’ implementation by taking into account local materials, traffic information, and environmental conditions. This study aims to improve the accuracy of MEPDG/pavement ME design pavement performance predictions for Iowa pavement systems through local calibration of MEPDG prediction models. A total of 70 sites from Iowa representing both jointed plain concrete pavements (JPCPs) and hot mix asphalt (HMA) pavements were selected. The accuracy of the nationally calibrated MEPDG prediction models for Iowa conditions was evaluated. The local calibration factors of MEPDG performance prediction models were identified using both linear and nonlinear opti...

Passenger Car and Truck Operating Speed Models on Multilane Highways with Combinations of Horizontal Curves and Steep Grades

Abstract: Operating speed prediction models have been proposed as a candidate method to assess design consistency on highways and streets. A significant number of operating speed prediction models exist for passenger cars on two-lane rural highways. Few models exist for passenger cars on multilane highways, while the literature is scant for operating speed models for trucks on multilane highways. This research uses a systems modeling approach to predict passenger car and truck operating speeds on multilane highways with combinations of horizontal curves and steep vertical grades. Mean operating speeds were modeled as a function of several geometric design features and the traffic control devices present at each study site. Further, the possible endogenous relationship between passenger car and truck speeds was investigated. The findings indicate that the radius of horizontal curve appears to have a larger influence on passenger car operating speeds than truck speeds. Vertical grades appear to have a more significant influence on truck operating speeds than on passenger car speeds. Increasing the right shoulder width is associated with higher passenger car operating speeds, but the lane width was not statistically significant in the passenger car speed models. Increasing the lane width, however, was associated with higher truck operating speeds; the right shoulder width was not associated with truck operating speeds. Higher posted speed limits were associated with higher truck and passenger car operating speeds. An endogenous relationship between truck and passenger car operating speeds was found.

Estimation of entry capacity for single-lane modern roundabouts: case study in Queensland, Australia

Abstract: Single-lane modern roundabouts are one of the most important intersection types in the suburbs of Australia. Therefore, it is important to estimate their entry capacities. In this case study, an analytical model based on the gap acceptance theory by incorporating the effects of the exiting vehicles is proposed. Then, a scenario analysis is carried out to assess the effects of the exiting indicators. This is followed by the discussion of the applicability of the proposed model. The results show that the transport authorities need to strictly enforce the use of indicators before exiting in order to achieve higher capacity.

Evaluating Snow and Ice Control Chemicals for Environmentally Sustainable Highway Maintenance Operations

Abstract: The use of chemicals and abrasives for highway winter maintenance operations is an essential strategy for ensuring a reasonably high level of service, yet the performance of such materials has to be balanced with their potential negative impacts on motor vehicles, transportation infrastructure, and the natural environment. In this context, this work presents a comprehensive and quantitative evaluation of snow and ice control chemicals currently used by various Idaho Transportation Department districts for highway maintenance operations, including rock salts (mainly solid sodium chloride), IceSlicer products (solid sodium chloride with trace amounts of other chlorides), and salt brines. The analysis has been enabled by the utilization of existing lab and field test data along with reasonable assumptions, in the effort to identify environmentally sustainable materials for winter highway operations. Despite its caveats, this case study is the first attempt to incorporate the most up-to-date informati...

Comparison between GA and PSO in Analyzing Pavement Management Activities

Abstract: This paper demonstrates the application of particle swarm optimization (PSO) to the programming of pavement maintenance activities at the network level. Furthermore, the application of the PSO technique and its relevance to solving the programming problem in a pavement management system (PMS) is discussed. The robustness and quick search capability of PSO enables it to effectively handle the highly constrained problem of pavement management activities programming, which has an extremely large solution space of astronomical scale. Examples are presented to highlight the versatility of PSO in accommodating different forms of objective functions and comparing the results with the genetic algorithm (GA). This paper compares PSO and GA with respect to rate of convergence and accuracy of modeling PMS using an example problem. The results of this paper confirmed the potential of PSO to successfully model the PMS.

Systematic Approach to Hazardous-Intersection Identification and Countermeasure Development

Abstract: Safety performance functions (SPFs) are commonly used to correlate geometric, traffic, and environmental characteristics with total crashes, and to identify hotspots that have excessive overall crash frequencies However, different crash types are associated with different vehicle maneuvers and therefore different risk factors At signalized intersections, geometric design, signal control, traffic flow, and traffic crash occurrences vary across different approaches of a single intersection This study developed approach-level SPFs using a full Bayesian method to assess the safety effects of specific risk factors for rear-end, left-turn, right-angle, and sideswipe crash types, and for total crashes Based on these approach-level SPFs, a systematic method that efficiently integrated the procedures of hotspot identification and countermeasure development was proposed The method can be used to identify high-risk intersection approaches with specific safety problems and can serve as a useful complemen

Measuring the Performance of Bus Rapid-Transit Corridors Based on Volume by Capacity Ratio

Abstract: Various approaches have been deployed for evaluating the performance of bus rapid transit (BRT) systems based on qualitative, economic and quantitative parameters. In the present study, the performance evaluation of the bus rapid transit system (BRTS) in Indian cities using a microsimulation technique has been attempted. Base networks of Delhi and Ahmedabad BRT corridors were developed, calibrated, and validated using specialized software. After the validation process, speed versus volume to capacity (V-C) ratio equations were developed for mixed vehicle (MV) and bus lanes, respectively, of both the corridors considered in the study. These equations were optimized to find out the optimum value of V-C ratio on the MV and bus lanes, which were found to range between 0.64 and 0.75. An average value of 0.688 V-C ratio was derived in this study for BRTS based on the calculated optimal values. Then, the concept of user equilibrium (UE) was deployed to understand when the travel speeds in both an MV lane and a bus lane of a BRT corridor reach the point of congestion. Based on this study, it can be concluded that 0.688 V-C ratio is the optimal flow value for BRT corridors. This implies that up to 0.688, both the MV lane users and bus lane users will enjoy reasonable travel speeds and smaller delays. If the V-C ratio is exceeded on either bus lane or MV lane(s), then the BRT system becomes untenable for the MV lane and bus lane users, instead creating traffic congestion.