Date: June 25, 2015
Status: Finished
Authors: Sung Yoon Park and Gang-Len Chang
Conference: 90th TRB Annual Meeting in 2011
Abstract:
Contending with recurrent congestion on commuting corridors has long been a challenging and pressing issue for responsible highway agencies. However, effective strategies to mitigate the congestion level and the accompanied safety issues on those highway segments remain to be developed. In response to such needs, this study presents an innovative system that integrates variable speed control and travel time information for alleviating the day-to-day congestion at a highway corridor.The entire system presented in this study includes a set of algorithms for setting variable speeds for different highway segments based on traffic conditions detected from roadway sensors, and a well-calibrated licensed-plate-recognition system for displaying the estimated travel time. Our field experiments of the proposed system on MD100 over eight weeks have revealed that with a proper speed control in real time the congested highway segment indeed can achieve a higher throughput, stable traffic condition, and shorter travel time. The display of estimated travel times seem to ease the stress of drivers and to increase their compliance to the suggested speed limits.
Authors: Mark Franz and Gang-Len Chang
Conference: 90th TRB Annual Meeting in 2011
Abstract:
The Maryland State Highway Administration has started a pilot program to evaluate the effectiveness of an automated speed enforcement system in work zones. Three sites were selected to measure the spatial and temporal effect of automated speed enforcement on motorists’ speeding behavior. In addition to comparing the temporal changes and spatial evolution of mean and 85 percentile speeds, the spatial and temporal change in percentages of three motorist populations, conservative, normal and aggressive drivers, were considered. A total of five datasets were analyzed. For the two data sets that compared the before versus during analysis periods, the enforcement period displayed a general reduction in aggressive motorists while creating a more stable spatial speeding distribution through the work zone. Two of the three data sets comparing the during versus after enforcement periods showed that motorists may learn where enforcement is taking place and adjust their speeds accordingly. This effect was evident even after the enforcement period. Lastly, one dataset displayed increased speeds and less stable spatial speeding patters during the enforcement period, suggesting the need for further investigation of this data set.
Authors: Zichuan Li and Gang-Len Chang
Conference: TRB 2010 Annual Meeting, January 13, 2010
Status: Presented
Abstract:
This study presents an arterial signal optimization model that is capable of capturing the queue blockage between intersection lane groups during oversaturated conditions. The proposed model is grounded on the original cell transmission concept proposed by Daganzo, but enhanced with a new diverging cell for formulating the complex interactions of queue spillback between left-turn and through traffic flows. With the embedded formulations for forward wave, backward wave, and the horizontal queue, the proposed arterial signal optimization model can yield effective signal plans for both saturated and under-saturated intersections. To evaluate the performance of the proposed model, this study has conducted extensive simulation experiments with a segment of Georgia Avenue connected directly to Capital Beltway in Maryland. The analysis results in comparison with the signal plans from TRANSYT-7F (Release 10) have demonstrated the promising properties of the proposed model.
Authors: Ning Yang and Yue Liu
Conference: The 15th World Congress on Intelligent Transport Systems, New York, 2008
Status: Presented
Abstract:
In this paper, we develop a simulation optimization procedure for optimizing the urban arterial traffic signal timings including a bunch of sequential intersections. The system performance is estimated via a stochastic discrete-event meso-scopic traffic simulator, and a gradient-based search algorithm on stochastic approximation is applied to give the optimal signal timings. Simultaneous perturbation analysis is used to derive both left-hand and right-hand gradient estimators of the system performance with respect to the cycle lengths, green splits, and green offsets for those intersections within the arterial. Numerical experiments show that the meso-scopic traffic simulator provides reasonable system performance in much less running time if properly calibrated, compared with a widely-used commercial traffic microscopic simulation program CORSIM. In particular, for all scenarios designed, the optimizer converges to optimal signal timing plans which significantly increase the system performance.