Angshuman Guin

Traffic Management Center Use of Incident Detection Algorithms: Findings of a Nationwide Survey

The focus of this paper is the context in which the decision makers for traffic management centers (TMCs) choose whether to include and/or use automatic incident detection (AID) algorithms. A survey was conducted of TMC professionals in positions to make, influence, or provide input to decisions regarding TMC operational policies as well as decisions regarding priorities for future system enhancements. Analysis of the survey results not only provides an understanding of the reasons behind the limited implementation of AID algorithms but also allows a direct comparison between the conventional incident detection methods and the AID technology on the basis of measured and/or perceived performance. It was observed that 90% of the survey respondents feel that the current methods of incident detection are insufficient either at present (70%) or will be so in the future (20%). This finding alone motivates a need to redouble research efforts aimed at developing robust and accurate automatic detection methods. In this regard, this paper presents promising directions to overcome past AID algorithm deficiencies

Travel Time Prediction Using a Seasonal Autoregressive Integrated Moving Average Time Series Model

Travel time estimation and prediction form an integral part of any advanced traveler information system. This paper presents a univariate time series based approach to predicting future travel times using historical travel time data. This model relies strictly on point detection data. Empirical testing of the model is performed using ITS data obtained from video detection systems in Atlanta, Georgia. The results of the model choice, validation and testing are reported and conclusions interpreting the findings in the model development process are provided

Analysis of Reduction in Effective Capacities of High-Occupancy Vehicle Lanes Related to Traffic Behavior

Previous research efforts have quantified the capacity of non-barrier-separated, high-occupancy vehicle (HOV) lanes. However, the majority of these efforts have focused on HOV lanes that usually operate well below capacity. In contrast, the I-85 HOV lanes in Atlanta, Georgia, usually operate under constrained flow conditions during morning and afternoon peak periods. This provides an opportunity to assess the relative performance of the HOV lane to the adjacent general-purpose (GP) lanes, which also undergo constrained flow conditions. This paper considers the relationship between the performance of the HOV and GP lanes by examining speed differential effects as a function of congestion on GP lanes. The research provides evidence of a sympathetic reduction in vehicle speeds in the HOV lane. This is likely explained by the safety concerns of the HOV drivers associated with the potential for vehicles using the congested GP lanes to enter the HOV lane, as well as the safety concerns of HOV drivers looking for an acceptable gap to merge into the GP lanes to access a downstream exit ramp.

Systematic Approach for Validating Traffic Simulation Models

Modeling processes and model testing processes are discussed as parts of the model life cycle, and the tasks of these processes and their relations are highlighted. Of particular interest is the model validation process, which ensures that the model closely simulates what the real system does. A collection of validation techniques is presented to facilitate a systematic check of model performance from various perspectives. Under the qualitative category, a few graphical techniques are presented to help a visual examination of the differences between the simulation and the observation. Under the quantitative category, several statistical measures are discussed to quantify the goodness of fit; to achieve a higher level of confidence about model performance, a simultaneous statistical inference technique is proposed that tests both model accuracy and precision. As an illustrative example, these validation techniques are comprehensively applied to test an enhanced macroscopic simulation model, KWaves, in a systematic manner.

Benefits Analysis for Incident Management Program Integrated with Intelligent Transportation Systems Operations: Case Study

A methodology was established to assess the various benefits of an incident management program that is part of an advanced transportation management system. The methodology computes the benefits derived from the motorist assistance service, the reduction in delay, fuel consumption, secondary crashes, and the improvement in air quality attributable to the incident management program. A case study involving the Georgia NaviGAtor, Georgias intelligent transportation system, reveals the resulting annual benefits of implementation of the methodology. The results indicated a substantial annual savings to motorists of 7.2 million vehicle hours of incident-related delay. The overall cost savings computed for a 12-month period during 2003 and 2004 was

Evolution of Oscillations in Congested Traffic: Improved Estimation Method and Additional Empirical Evidence

187 million. On the basis of an annualized infrastructure, operations, and maintenance cost of the NaviGAtor system, the annual benefits-cost ratio was calculated to be 4.4:1.

Modeling pedestrian crossing activities in an urban environment using microscopic traffic simulation

This paper provides additional empirical evidence confirming a recently proposed theory on the evolution of oscillations in congested traffic. It also proposes an improved method for computing the variation in oscillation amplitude, consisting in evaluating the oscillation amplitude along characteristic lines that travel at a constant wave speed. It is also shown that the theory is robust in that approximate input parameters can be used with little loss in accuracy. The paper, in addition, provides a finding on the evolution of oscillations in freeway segments with no entrances or exits. Although previous studies found an increase in oscillation amplitude in such segments, data in this study indicate that this is not the case in general. This finding can have important implications for understanding driver behavior in homogeneous freeway segments.

A Dynamic Data Driven Application System for Vehicle Tracking

Microscopic traffic simulation tools are increasingly being employed as an integral part of modeling vehicular traffic and pedestrian activity. However, the complexity of pedestrians’ behaviors and their interactions with the various components of the traffic network is commonly under-represented in simulation models, resulting in potentially misleading analyses. This paper explores modeling pedestrians at the microscopic level, attempting to replicate observed pedestrian behavior at a crosswalk in Midtown Atlanta, GA. The VISSIM® simulation tool, with pedestrian movement based on the Social Force Model by Helbing and Molnár (Social Force Model for pedestrian dynamics. Phys Rev E 1995; 51: 4282-4286), is utilized. Comparative results of field observations and the microscopic modeling of the same vehicle and pedestrian activity are presented. A primary observation is that, for the intersection studied, only a small percentage of pedestrians appear to comply with the pedestrian signal indication, with the vast majority of pedestrians exhibiting gap-seeking behavior, crossing when a gap is available, regardless of the signal indication. This results in potentially significant over-estimates of wait time if high pedestrian signal compliance rates are assumed. A second notable observation is that the pedestrian crossing behavior is strongly related to the cross-street traffic queue clearance time and subsequent traffic flow. Capturing this interaction significantly enhances the models’ ability to reflect the observed field performance.

Evaluation of Effectiveness of Converging Chevron Pavement Markings in Reducing Speed on Freeway Ramps

Abstract Tracking the movement of vehicles in urban environments using fixed position sensors, mobile sensors, and crowd-sourced data is a challenging but important problem in applications such as law enforcement and defense. A dynamic data driven application system (DDDAS) is described to track a vehicles movements by repeatedly identifying the vehicle under investigation from live image and video data, predicting probable future locations, and repositioning sensors or retargeting requests for information in order to reacquire the vehicle. An overview of the envisioned system is described that includes image processing algorithms to detect and recapture the vehicle from live image data, a computational framework to predict probable vehicle locations at future points in time, and a power aware data distribution management system to disseminate data and requests for information over ad hoc wireless communication networks. A testbed under development in the midtown area of Atlanta, Georgia in the United States is briefly described.

Conceptual Framework for Collecting Online Airline Pricing Data: Challenges, Opportunities, and Preliminary Results

Converging chevron pavement markings have recently seen rising interest in the United States as a means to reduce speeds at high-speed locations and improve safety performance. This paper reports on an investigation into the effectiveness of chevron markings in reducing vehicle speeds on two-lane freeway-to-freeway directional ramps in Atlanta, Georgia. The evaluation is based on a statistical comparison at preselected sites of speeds before and after the installation of the chevron markings. The analysis focuses on the effect of converging chevrons over the range of speed percentiles and on the mean speed. The analysis indicates that chevrons have a minimal effect on vehicle speeds, with drivers adjusting back to their previous speeds as they acclimate to the treatment. The effect of the chevrons’ treatments on speed tended to be most pronounced immediately after the chevron implementation. However, by the 9th month after implementation the magnitude of the effect dropped to under 1 to 2 mph for the mean speed and most vehicle speed percentiles. Although this result does not necessarily imply that the chevron treatment is not a meaningful safety treatment, any safety benefits are not likely to result from a general decrease in speeds.