André-Gilles Dumont

Fusing Loop Detector and Probe Vehicle Data to Estimate Travel Time Statistics on Signalized Urban Networks

This article presents a methodology that integrates cumulative plots with probe vehicle data for estimation of travel time statistics (average, quartile) on urban networks. The integration reduces relative deviation among the cumulative plots so that the classical analytical procedure of defining the area between the plots as the total travel time can be applied. For quartile estimation, a slicing technique is proposed. The methodology is validated with real data from Lucerne, Switzerland and it is concluded that the travel time estimates from the proposed methodology are statistically equivalent to the observed values.

Estimation of Travel Time on Urban Networks with Midlink Sources and Sinks

This paper presents a methodology for estimation of average travel time on signalized urban networks by integrating cumulative plots and probe data. This integration aims to reduce the relative deviations in the cumulative plots due to midlink sources and sinks. During undersaturated traffic conditions, the concept of a virtual probe is introduced, and therefore, accurate travel time can be obtained when a real probe is unavailable. For oversaturated traffic conditions, only one probe per travel time estimation interval–-360 s or 3% of vehicles traversing the link as a probe–-has the potential to provide accurate travel time.

Analysis for the Use of Cumulative Plots for Travel Time Estimation on Signalized Network

This paper provides fundamental understanding for the use of cumulative plots for travel time estimation on signalized urban networks. Analytical modeling is performed to generate cumulative plots based on the availability of data: a) Case-D, for detector data only; b) Case-DS, for detector data and signal timings; and c) Case-DSS, for detector data, signal timings and saturation flow rate. The empirical study and sensitivity analysis based on simulation experiments have observed the consistency in performance for Case-DS and Case-DSS, whereas, for Case-D the performance is inconsistent. Case-D is sensitive to detection interval and signal timings within the interval. When detection interval is integral multiple of signal cycle then it has low accuracy and low reliability. Whereas, for detection interval around 1.5 times signal cycle both accuracy and reliability are high.

Random forest models for identifying motorway Rear-End Crash Risks using disaggregate data

This paper presents an approach to develop motorway Rear-End Crash Risk Identification Models (RECRIM) using disaggregate traffic data, meteorological data and crash database for a study site at a two-lane-per-direction section on Swiss (right-hand driving) motorway A1. Traffic data collected from inductive double loop detectors provide instant vehicle information such as speed, time headway, etc. We define traffic situations (TS) characterized by 22 variables representing traffic status for 5-minute intervals. Our goal is to develop models that can separate TS under non-crash conditions and TS under pre-crash conditions using Random Forest - an ensemble learning method. Non-crash TS were clustered into groups that we call traffic regimes (TR). Precrash TS are classified into TR so that a RECRIM for each TR is developed. Interpreting results of the models suggests that speed variance on the right lane and speed difference between two lanes are the two main causes of the rear-end crashes. The applicability of RECRIM in a real-time framework is also discussed.

Transport Simulation: Beyond Traditional Approaches

In recent years, the transport simulation of large road networks has become far more rapid and detailed, and many exciting developments in this field have emerged. In this perspective, the authors describe the simulation of automobile, pedestrian and rail traffic, coupled to new applications, such as the embedding of traffic simulation into driving simulators, to give a more realistic environment of driver behavior surrounding the subject vehicle. New approaches to traffic simulation are described, including the hybrid mesoscopic-microscopic model and floor-field agent-based simulation. The book has been written by an invited panel of experts, thus covering the relevant sub-disciplines, and is addresed to students, engineers, and scholars, as well as those who require a state-of-the-art overview of traffic simulation today.

Average Travel Time Estimations for Urban Routes That Consider Exit Turning Movements

This paper presents a methodology for real-time estimation of exit movement–specific average travel time on urban routes by integrating real-time cumulative plots, probe vehicles, and historic cumulative plots. Two approaches, component based and extreme based, are discussed for route travel time estimation. The methodology is tested with simulation and is validated with real data from Lucerne, Switzerland, that demonstrate its potential for accurate estimation. Both approaches provide similar results. The component-based approach is more reliable, with a greater chance of obtaining a probe vehicle in each interval, although additional data from each component is required. The extreme-based approach is simple and requires only data from upstream and downstream of the route, but the chances of obtaining a probe that traverses the entire route might be low. The performance of the methodology is also compared with a probe-only method. The proposed methodology requires only a few probes for accurate estimation; the probe-only method requires significantly more probes.

Impact of different ageing levels on binder rheology

This paper evaluates the variability of binder rheology for different ageing levels and the influence of ageing at different testing temperatures. Three different ageing levels were applied on a single type of bitumen with a penetration grade of 70/100.The artificial ageing of the binder was performed using the rolling thin-film oven test and the pressure ageing vessel. The rheological behaviour was investigated at low temperatures with the bending beam rheometer (BBR) and at medium and high temperatures with the dynamic shear rheometer (DSR). Several experiments were conducted to determine the range of stiffness and complex modulus results, the type of distribution comparing real and theoretical models, and the effects of ageing on the variability of the rheological behaviour. It was shown that not only the mean results from BBR and DSR tests change with ageing, but also the variability of the results changes with ageing. This would have an impact on mechanistic-empirical pavement design because it would influence the calculated stresses and strains as well as the calculated reliability.

Microsimulation Modeling of Coordination of Automated Guided Vehicles at Intersections

One of the challenges with autonomous vehicles is their performance at intersections. An alternative control method for the coordination of autonomous vehicles at intersections is shown. The proposed approach was grounded in multiple-robot coordination and took into account vehicle dynamics as well as realistic communications constraints. The existing concept of decentralized navigation functions was combined with a sensing model, and a crossing strategy was developed. The simulation results showed that because of the proposed approach, vehicles had smoother trajectories when crossing at a four-way intersection. The proposed method was compared with adaptive traffic lights and roundabouts in terms of throughput. Results showed that using a decentralized navigation function for the coordination of autonomous vehicles improved their performance by reducing energy consumption and pollution emissions.

Investigation of Lane Flow Distribution on Hard Shoulder Running Freeways

In response to an impending demand growth at an existing reactive managed lane system and to provide a timely and more effective temporary hard shoulder activation, this paper presents the development of short-term prediction models. A lane-oriented attribute—namely, the left-lane flow distribution ratio—is introduced to ameliorate the system by capturing the forthcoming stream dynamics and reconfiguring it to be proactive. To assess the impact on the networks performance of implementing a system for hard shoulder running, an exploratory analysis was performed on the basis of data acquired by seven radar sensors located every 500 m along a Swiss freeway section that was not affected by incoming or exiting traffic. A locally weighted regression was employed to provide more accurate insight into traffic behavior by comparing observations derived during the regular operation of the system and a period in which it was suspended, with respect to seasonality patterns. To describe the impending stream motion by examining different time–volume clusters (off-peak and peak hours), two prediction models were specified according to the time range. The preliminary results of the study for several prediction horizons demonstrate an acceptable prediction uncertainty. The hard shoulder activation prediction confirms the analysis of the findings of this research with regard to the impact on operations.

Strain and stress distributions in flexible pavements under moving loads

ABSTRACT Calculated strain distributions in flexible pavements were studied by comparison with measurements made on full-scale structures. The calculated results were obtained by elastic and viscoelastic modelling of these structures. As no stress measurements were collected, the stress distribution was studied by comparing the results of elastic and viscoelastic calculations. For different loading and temperature conditions, and assuming the hypothesis of the French design method for flexible pavements, modelling provided strain signals similar to those measured on real scale structures for strains at two different depths in the studied structures. This first conclusion was used to validate the models, which were then used in the stress study. Some unexpected strains variations were observed near to the surface of the structures. Modelling based on linear elastic behaviour of the materials made it possible to explain these variations by analysing the stress variations, particularly in the vertical direction. Viscoelastic modelling have shown that some additional stresses appear in the bituminous layer when the loads are moving away from the measurement point. These stresses are induced mainly by the reaction of the foundation layers (sub-base and sub-grade) and they are mainly caused by the interaction between the layers of the structures. Finally, the analysis of the strain and stress distributions near to the surface showed that bituminous materials are submitted to higher horizontal than vertical stresses just under the truck wheel. A particular and unexpected result of this situation is that the vertical strains at just under the wheel are tensile ones.