Individual variable speed limit trajectory planning considering stochastic arriving patterns

Connected vehicles enabled by communication technologies have the potential to improve trafc mobility and enhance roadway safety such that trafc information can be shared among vehicles and infrastructure.Fruitful speed advisory strategies have been proposed to smooth connected vehicle trajectories for better system performance with the help of diferent carfollowing models.Yet,there has been no such comparison about the impacts of various car-following models on the advisory strategies.Further,most of the existing studies consider a deterministic vehicle arriving pattern.The resulting model is easy to approach yet not realistic in representing realistic trafc patterns.This study proposes an Individual Variable Speed Limit(IVSL)trajectory planning problem at a signalized intersection and investigates the impacts of three popular car-following models on the IVSL.Both deterministic and stochastic IVSL models are formulated,and their performance is tested with numerical experiments.The results show that,compared to the benchmark(i.e.,without speed control),the proposed IVSL strategy with a deterministic arriving pattern achieves signifcant improvements in both mobility and fuel efciency across diferent trafc levels with all three car-following models.The improvement of the IVSL with the Gipps’model is the most remarkable.When the vehicle arriving patterns are stochastic,the IVSL improves travel time,fuel consumption,and system cost by 8.95%,19.11%,and 11.37%,respectively,compared to the benchmark without speed control.

An analysis on possibility of intelligent speed adaptation in terms of drivers' consciousness

Intelligent speed adaptation （ISA） is considered as an effective measure to reduce number of traffic accidents in the field of intelligent transportation systems （ITS）. On the other hand, its effects for traffic safety are still doubted by many people. To make the possibility analysis, an experiment is conducted by using driving simulator. Regarding ISA ap- proaches, there are three modes： mandatory, voluntary and advisory. Among them, the advisory type seems to be the easiest one to introduce. Therefore, we focus on the advisory mode in this study by considering ISA just at the beginning stage in Japan. The experiment consists of four steps： without ISA, ISA using pictures, ISA using voices and again without ISA. The outputs obtained from the driving simulator are analyzed combined with the consciousness of the participants. The experiment shows that the ISA can improve recognition of speed limitation especially for people who have random rambling or looking aside tendency. Furthermore, the ISA especially when using voices can contribute in changing the consciousness of people who are aggressive in driving. Their driving speeds can reduce so that positive effects on traffic safety can be concluded.

Implications of advanced warning messages on eliminating sun glare disturbances at signalized intersections

Due to sun glare disturbances, drivers encounter fatal threats on roadways, particularly at signalized intersections. Many studies have attempted to develop applicable solutions, such as avoiding sun positions, applying road geometric re-directions, and wearing anti- glare glasses. None of these strategies have fully solved the problem. As one of the ＂Con- nected Vehicle＂ practices proposed by the U.S. Department of Transportation, advanced warning messages （AWMs） are capable of providing wireless information about traffic controls. AWM acts as a supplement to conventional signs and signals, which can be blocked by obstacles or natural disturbances, such as sun glare. The drivers＇ smart advisory system （DSAS） can provide drivers with AWM. Using a driving simulator this research explores the effects of DSAS messages on driving behaviors under sun glare disturbance. Statistical analyses were applied to assess （1） the negative impacts of sun glare, （2） the compensation of the DSAS AWM to sun glare effects, and （3） the improvement in driving performance due to DSAS AWM. Four performance indexes were measured, including （1） half kinetic energy speed, （2） mean approach speed, （3） brake response time, and （4） braking distance. The effects of the socio-demographic factors, such as gender, age, educational background, and driving experience were also studied. The analytical results illustrate that the DSAS can compensate for reduced visibility due to sun glare and improve driving performance to a normal visual situation, particularly for left turn and through movement.