Ear Program Research Results

PROJECT:

High-Performance Stress-Relaxing Cementitious Composites for Crack-Free Pavements and Transportation Structures

INSTITUTIONS:

Texas A&M University, Texas Transportation Institute

COMPLETED:

July 2011

OBJECTIVE:

To achieve a durable concrete with enhanced viscoelastic

CONTACT:

Richard Meininger,  202-493-3191
(richard.meininger@dot.gov)

RESOURCES:

Technical report at http://d2dtl5nnlpfr0r.cloudfront.net/swutc.tamu.edu/publications/technicalreports/476660-00017-1.pdf

Research article at http://www.hindawi.com/journals/jnm/2012/371927

RESULTS: Investigators performed a comprehensive review of previous work using carbon nanofilaments (CNFs) and tubes (CNTs) in cementitious materials to improve their mechanical properties and behaviors, and conducted a detailed study of the common method of incorporating CNFs. They developed a novel thermodynamic-based dispersion quantification method to measure the effect of geometry-dependent clustering on CNF dispersion in cement paste. They also developed a new method for improving and stabilizing CNF dispersion in cement paste using silica fume to significantly improve CNF dispersion in a hardened cementitious matrix. Finally, experimental investigation of the effect of CNFs on the mechanical behavior and properties of hardened cement paste showed that CNFs can increase flexural strength and reduce shrinkage cracking. The researchers produced an advanced hardened cement paste that is strong and resists shrinkage cracking quite well under certain levels of restraint. Next steps could include additional exploratory advanced research.

IMPACT: Use of new materials such as CNTs can lead to increased durability of pavements and structures as well as to multifunctional materials such as self-sensing pavements.

PROJECT:

Driver Behavior in Traffic

INSTITUTIONS:

Virginia Polytechnic Institute and State University in partnership with PTV America and the Virginia Center for Transportation Innovation and Research

COMPLETED:

February 2012

OBJECTIVE:

To characterize driver behavior using naturalistic driving data and agent-based modeling techniques for development of effective strategies to improve transportation safety and operations.

CONTACT:

David Yang, 202-493-3284
(david.yang@dot.gov)

RESOURCES:

Final report at http://www.ntis.gov. Search: PB2012-105330.

RESULTS: This research provides a foundation for agent-based modeling of driver behavior based on naturalistic data through an integrated framework for safety and operation analysis. Lateral vehicle action was simulated in a microscopic traffic behavior modeling environment, bringing new insights to the modeling of driver maneuvering behavior during safety-critical events. Agents developed and evaluated in the VISSIM simulation platform revealed a close resemblance to real driver data. The project team improved car-following models through development of a hybrid model for greater accuracy and flexibility and through the addition of the new “passing and hook-following” thresholds. They used the model to simulate vehicle actions in safety-critical events, developed agent-based simulation components integrated with the VISSIM simulation package through its driver model, and developed and implemented a robust activation mechanism for agent-based simulation based on discriminant analysis. The investigators also identified key future research issues: adaptability of agents in real time and human factors issues related to warning individual drivers about changes in their driving behavior that might lead to safety-critical events.

IMPACT: New behavioral models are necessary to predict the safe and efficient use of new connected vehicle and roadside technology. This project demonstrates the ability of agent-based models based on naturalistic driving studies to create new and improved behavioral models.

PROJECT:

Modeling the Urban Continuum in an Integrated Framework: Location Choice, Activity-Travel Behavior, and Dynamic Traffic Patterns

INSTITUTIONS:

Arizona State University with the University of Arizona and the University of Washington

COMPLETED:

March 2012

OBJECTIVE:

To develop a conceptual framework, integrated prototype, and computational tools for modeling interactions between the built environment and multimodal transportation systems and modeling urban systems across simulated land use, travel demand, and traffic flow.

CONTACT:

Brian Gardner, 202-366-4061
(brian.gardner@dot.gov)

RESOURCES:

Project Web site at http://urbanmodel.asu.edu/intmod.html

RESULTS: SimTRAVEL, developed in this project, is an integrated modeling system that advances land-use and transportation microsimulation by providing seamless modeling of longer term choices about location (home, work, school) and shorter term choices of activity, travel mode, and route. SimTRAVEL integrates the use of UrbanSim (a land-use model), OpenAMOS (an activity-based microsimulation model), PopGen (a state-of-the-art synthetic population generator), and DynusT/MALTA (a dynamic traffic assignment and microsimulation model) within a behaviorally robust framework. The integrated systems have been fully implemented in a user-friendly software environment with powerful graphical user interfaces and visualization dashboards. Open-source software architecture with multithreading and parallel-computing capabilities speeds simulations. SimTRAVEL was successfully tested and validated on a 500,000 population subregion of Maricopa County, AZ.

IMPACT: The innovations in this modeling software, which is freely available to the modeling community, are expected to have a major impact on transportation planning for sustainable futures.

PROJECT:

Layered Object Recognition System for Pedestrian Collision Sensing

INSTITUTIONS:

Layered Object Recognition System for Pedestrian Collision Sensing

COMPLETED:

Sarnoff Corporation with AutoLiv Electronics America

OBJECTIVE:

To develop a real–time, in–vehicle, vision–only system to detect pedestrians and determine potential collisions with high accuracy and minimal false alarms.

CONTACT:

Wei Zhang, 202–493–3317
(wei.zhang@dot.gov)

RESOURCES:

Conference paper at http://onlinepubs.trb.org/onlinepubs/conferences/2011/RSS/2/Zhang,W.pdf

Final report at https://www.fhwa.dot.gov/publications/research/

Visual output of the pedestrian-detection system as it recognizes crossing pedestrians.

RESULTS: The project team developed an in-vehicle, stereo vision–based system that detects, recognizes, and tracks pedestrians in its field of view. The system uses contextual information to reduce false alarms and light-enhancing techniques to improve low-visibility detection. Evaluated on publicly available datasets, the system matched or exceeded the performance of leading pedestrian detectors, tracking pedestrians at vehicle speeds of up to 48 km/h (30 mi/h) and distances up to 35 m (115 ft) away under good visibility conditions and up to 25 m (82 ft) away under reduced visibility with a 90-percent overall positive detection rate. The researchers recommend further development to upgrade performance. The feasibility of commercial implementation is high, since the system uses low-cost components.

IMPACT: Twilight hours are the most dangerous time for pedestrians. Existing detection systems, however, have limited effectiveness in low-light conditions. New approaches introduced in this study provide superior results in twilight.

PROJECT:

Development and Evaluation of Selected Mobility Applications for VII

INSTITUTIONS:

California PATH (Partners for Advanced Transit and Highways), University of California, Berkeley, and Caltrans

COMPLETED:

July 2011

OBJECTIVE:

Develop new strategies to reduce bottlenecks, minimize congestion, and maximize throughput by utilizing the capabilities of intelligent vehicles and highway infrastructure.

CONTACT:

Bob Ferlis, 202-493-3268
(robert.ferlis@dot.gov)

RESOURCES:

Final report at http://www.dot.ca.gov/newtech/researchreports/reports/2011/task_2138-tsm.pdf

Project Web site at http://gateway.path.berkeley.edu/~xylu/files/Truck_Control.html

RESULTS: The project team modeled, tested, and demonstrated prototype wireless communication systems to improve traffic flow by calculating and communicating variable speed limits (VSL) to drivers; achieve higher effective lane capacities using cooperative adaptive cruise control (CACC); and reduce fuel consumption and increase truck-only lane capacity with automated platoons.

Variable Speed Limits—In simulation and live tests on I-80, the researchers broadcast speeds calculated to prevent traffic flow breakdowns, with promising results. VSLs show significant potential to prevent traffic delays.

Cooperative Adaptive Cruise Control—Study results show that CACC could substantially increase highway capacity when it reaches moderate to high market penetration. Retrofitting non-CACC vehicles with inexpensive “here I am” radios could accelerate achievement of these capacity benefits.

Automated Truck Platoon Control—A wireless communications system successfully coordinated a platoon of three tractor-trailer trucks traveling at 85 km/h (53 mi/h) and in varied joining and splitting maneuvers. Fuel savings were estimated at 10 to 14 percent for the following trucks.

IMPACT: New connected vehicle and highway systems can lead to substantial safety, operational, and environmental benefits.

PROJECT:

Flexible Skin Areal Shear Stress and Pressure Sensing System for Experimental Bridge Scour Research

INSTITUTIONS:

National Aeronautics and Space Administration Jet Propulsion Lab and FHWA Hydraulics Research Laboratory

COMPLETED:

May 2011

OBJECTIVE:

To advance technology for measuring and understanding the complex flow fields and boundary shear stresses and pressure fields associated with bridge pier scour.

CONTACT:

Kornel Kerenyi, 202-493-3142
(kornel.kerenyi@dot.gov)

RESOURCES:

Technical report at http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/41997/1/11-0813.pdf

The flexible (skin) sensing system is based on an elastically mounted, floating plate concept. A single pressure sensor was inserted in the middle of this array. The optical encoder of each shear force sensor is encapsulated so the assembled sensor can be immersed in water.

RESULTS: In this project, the Jet Propulsion Laboratory conducted research on an integrated, flexible-skin, areal shear- and pressure-sensor system in a miniaturized array that measures changes in shear stress and pressure associated with scour-hole formation. The sensor elements were intended to measure shear forces in the range of 0.05 to 6 Pa and variations in pressure in the range of 0 to ±100 Pa, with a sampling rate of more than 500 data points per second. Such a system will help researchers understand erosive flow mechanisms related to turbulence structures, together with local flow convergence and contractions around the fronts and flanks of piers or between piles of complex pier configurations. Direct measurements of shear forces are essential to validated computational fluid dynamic models.

IMPACT: Scour is the predominate cause of failure in bridges over water. The ability to capture shear stress and pressure data will significantly aid small-scale scour experiments in bridge scour research.

PROJECT:

Development of Stiffness Measuring Device for Pad Foot Roller Compaction

INSTITUTIONS:

Colorado School of Mines, with Caterpillar Inc., BOMAG, and the Colorado Department of Transportation

COMPLETED:

June 2011

OBJECTIVE:

To develop a methodology to achieve continuous, real-time sensing of soil properties during static compaction with a pad foot roller.

CONTACT:

Mike Adams, 202-493-3025
(mike.adams@dot.gov)

RESOURCES:

Poster presentation at http://smartgeo.mines.edu/upload/poster_soil.pdf

Conference paper at http://control.mines.edu/mooney/docs/RealTimeSoilCompactionMonitoringPadStrain.pdf

Strain gages, installed within selected pads that are welded to the drum, are wired to a signal processing box that transmits data wirelessly to a computer in the cab.

RESULTS: Measurement of soil stiffness during compaction of foundations for highway structures is critical to ensuring that design-life specifications are met. In this study, investigators developed a conceptual framework for determining pad–soil contact force and displacement (and thus soil stiffness) from sensors built into the pads and roller, constructed a prototype measurement system, and devised a wireless data acquisition system to enable field-scale testing. They successfully measured plastic and elastic soil deformation during compaction using laser-based distance sensors and pad-strain-based techniques. Laboratory and field testing confirmed the predicted strain field changes. Some elements of the model need further refinement to ensure repeatable and accurate measurement across various soil conditions.

IMPACT: Intelligent compaction allows 100 percent quality control in real time. More comprehensive, accelerated measurement of compaction could improve long-term performance of roadway base courses and extend pavement life.