Safety Monitoring System of CAVs Considering the Trade-Off between Sampling Interval and Data Reliability

Abstract

The safety of urban transportation systems is considered a public health issue worldwide, and many researchers have contributed to improving it. Connected automated vehicles (CAVs) and cooperative intelligent transportation systems (C-ITSs) are considered solutions to ensure the safety of urban transportation systems using various sensors and communication devices. However, realizing a data flow framework, including data collection, data transmission, and data processing, in South Korea is challenging, as CAVs produce a massive amount of data every minute, which cannot be transmitted via existing communication networks. Thus, raw data must be sampled and transmitted to the server for further processing. The data acquired must be highly accurate to ensure the safety of the different agents in C-ITS. On the other hand, raw data must be reduced through sampling to ensure transmission using existing communication systems. Thus, in this study, C-ITS architecture and data flow are designed, including messages and protocols for the safety monitoring system of CAVs, and the optimal sampling interval determined for data transmission while considering the trade-off between communication efficiency and accuracy of the safety performance indicators. Three safety performance indicators were introduced: severe deceleration, lateral position variance, and inverse time to collision. A field test was conducted to collect data from various sensors installed in the CAV, determining the optimal sampling interval. In addition, the Kolmogorov–Smirnov test was conducted to ensure statistical consistency between the sampled and raw datasets. The effects of the sampling interval on message delay, data accuracy, and communication efficiency in terms of the data compression ratio were analyzed. Consequently, a sampling interval of 0.2 s is recommended for optimizing the system’s overall efficiency.

Constraints and Evaluations on Signature Transmission Interval for Aggregate Signatures with Interactive Tracing Functionality

“…The results of the implementation experiment indicates that if the acceptable feedback time of a system is significantly larger than a few hundred ms, e.g., industrial sensor systems [31], AS-FT-2 can be used without problems. On the other hand, there may be some applications where such sufficiently large feedback time is not acceptable, e.g., cooperative intelligent transportation systems [16]. In anticipation of such applications, we also proposed an ASIT scheme AS-SW-1 that does not require a feedback.…”

“…However, these schemes cannot be used if applications require faster feedback time. For instance, the average requirement for the transmission interval is considered to be 5 seconds to an hour [15], whereas in some real-time communication systems, the data transmission interval for cooperative intelligent transportation systems is considered to be 200 ms [16]. The existing scheme would not be suitable for the latter case.…”

“…On the other hand, in some real-time communication systems, according to [16], to guarantee traffic safety under bandwidth constraints, the data transmission interval for a cooperative intelligent transportation system is considered to be 200 ms, which is to optimize the overall efficiency of a system in features of safety indicators. From these requirements and Table 1, the feedback waiting time of AS-FT-2 is too long.…”

“…In some real-time communication systems, e.g., cooperative intelligent transportation systems, some high bandwidth communication protocols, such as LTE (23.6 Mbps), are used. In addition, to optimize the overall efficiency of a system in features of safety indicators, many devices send data in short interval, which is about 200 ms [16]. Therefore, AS-FT-2 cannot be used because of the feedback waiting time.…”

Analyzing the Impact of C-ITS Services on Driving Behavior: A Case Study of the Daejeon–Sejong C-ITS Pilot Project in South Korea

“…In contrast, C-ITS enables the real-time collection of various traffic information remotely through terminals and provides that information to other drivers, facilitating rapid and safe responses to sudden incidents [1,2]. By identifying potential hazards and preventing accidents in advance, C-ITS distinguishes itself from traditional ITS and is therefore an essential technology for creating a future autonomous driving environment [3][4][5][6]. In conventional ITS, the collection and provision of traffic information relies on specific locations where traffic information collection and dissemination devices were installed.…”