The modal share of buses in the country has generally increased due to the introduction of the intelligent transport system (ITS), transfer discounts, the One Card All Pass, and BRT expansion. However, in these days, an increasing trend in the modal share of buses in the country has been slowing down and switching to a decreasing trend due to an increase in the number of privately-owned passenger vehicles, the expansion of the KTX network, etc. The main reasons for an increase in the modal share of buses has such limitations as an increase in the expectation level on mobility due to the appearance of new means of transportation such as shared transportation, a decline in the mobility service level due to the lack of bus drivers, a decline in the profitability of bus operators, and the bus-related accidents.
The innovation of public transportation from the viewpoint of transit automation is being promoted in order to overcome the aforementioned limitations of public transportation and to increase the competitiveness of public bus transportation by providing a new service including a seamless inter-modal service, integration service of multi-modal services, and the first-last mile mobility service. The development of technologies and policies regarding transit automation is actively being carried out both domestically and abroad based on autonomous driving vehicles, demand-responsive mobility technology, and connected smart infrastructure. However, the development of technologies and policies related to Transit Automation at home and abroad is still at its early stage in comparison to that of the automation of passenger vehicles and trucks. In particular, the autonomous passenger vehicle and truck driving technology and service are at the commercialization stage based on various deployment projects with connected infrastructure technology. However, the autonomous bus driving technology is still at the sensor-based autonomous driving stage. As such, the technology is insufficient for commercialization in terms of securing expandability and safety.
In this study, the definition of the automated and connected driving-based smart public transportation system in comparison to the previous ITS-based public transportation system and the classification of public transportation service were presented through the review of domestic and overseas cases. Furthermore, the necessary technology and infrastructure requirements were drawn by analyzing autonomous driving vehicle and automated driving-related infrastructure technologies and reviewing public transportation application measures in order to revitalize the automation of public transportation and relevant businesses. Lastly, the connected and automated driving-based public transportation introduction strategy and the system drawing plan that fitted the current status of public transportation infrastructure in the country were presented based on such analyses.
1) Definition of automated and connected driving-based smart public transportation system and the classification of services through the case review
The previous public transportation system consists of the means of transportation, transportation facilities and traffic operation, and users, since the collection and provision of traffic information in real time have become available due to the introduction of advanced transportation systems and technologies such as ITS, it has provided more prompt, safe, and convenient smart transportation to the users and operators. In terms of the public transportation system, it consists of buses/taxis (means of transportation), the infrastructure (transportation facilities), management center (traffic operation), and passengers (users), and the transportation information management system-based ITS service is currently provided. The characteristic of the previous public transportation system is the systematic connection system between transportation facilities and users (passengers and operators) based on the real-time operation information of transportation. In comparison to this characteristic, the automated and connected driving-based smart public transportation system is the linkage system where the automation and sharing of the public transportation service is being advanced according to the connection and development between the means of transportation, transportation facilities and users (operators and passengers), and the basic mobility as well as the safety. All of these components are secured according to the characteristics of public transportation and this transportation system provides the customized transportation service for users based on the efficiency in the operation.
The services in the automated and connected driving-based smart public transportation system that were previously defined were classified into seven services according to the following: vehicle type, availability of exclusive lanes, form of bus stop operation, number of bus stops, route operation method, method of use or approach by users, and operation method.
- S1. AV Fixed-Route Transit Service_BRT: Public transportation system for operating automated and connected driving vehicles (large-sized buses) on an exclusive lane with fixed routes
- S2. AV Fixed-Route Transit Service_Branch line: Public transportation system for operating autonomous driving vehicles (large-sized buses) on normal roads with fixed routes
- S3. AV On-Demand Transit Service_Group: Public transportation system for operating automated and connected driving vehicles (public bus, shuttle bus, etc.) on normal roads according to certain demand response of users such as commuting. There are a limited number of points of departure and destinations, and some routes are fixed.
- S4. AV On-Demand Transit Service_By-Pass: Public transportation system for operating automated and connected driving vehicles (public bus, shuttle bus, etc.) on normal roads according to the response to users’ demand. Nonstop operation or by-passing operation at a place where there is no user demand for public transportation in comparison to general public transportation which requires stopping at all stations.
- S5. AV Paratransit (On-Demand)_Downtown area: Public transportation service based on automated and connected driving shuttle buses operated according to the demand of users in the downtown area. Users are allowed to use the service by using the phone and a smartphone app in order to improve the operator’s efficiency and user convenience. The routes and bus stops within a certain area can be optimized freely for the operation.
- S6. AV Paratransit (On-Demand)_Deprived area: automated and connected driving shuttle bus-based public transportation service operated according to the demand of users in deprived areas such as a rural area. Since the number of users is less in comparison to that of the downtown area, focus is made on the securing of mobility and efficiency in the operator based on advance reservation rather than the optimization of operation. It is possible to integrate and provide the mobility service with other systems such as the parcel system service and unmanned movie system.
- S7. AV Taxi: Passenger vehicle-based mobility service operated fully on a reservation basis according to the demand of users.
2) Drawing of necessary technologies and infrastructure level for each public transportation service
The autonomous driving vehicle technologies and autonomous driving-related infrastructure technologies were analyzed through the case study and literature analysis. Accordingly, the necessary technologies for providing the seven services drawn earlier were classified. In the analysis of autonomous driving vehicle technologies, 15 autonomous driving-related technology use cases were drawn by analyzing the visioning system (radar sensor, LIDAR sensor, computer vision system, ultrasonic sensor) and actuator system (steering technology, braking technology, power-train technology). In the analysis of autonomous driving-related infrastructure technologies, 26 autonomous driving-related technology use cases were drawn by analyzing the cloud (dynamic scheduling technology, real-time information provision technology, big data technology), mapping (HD map, dynamic map, live map, map transfer technology, geocoding), and communication (dedicated short-range communication, cellular/wireless communication, vehicle positioning and mobility technology, processing and software technology).
As a result of drawing necessary technologies related to public transportation automation based on the expert survey, all autonomous driving vehicle-related technologies were necessary with the exception of a number of technologies, including the drowsy driving prevention technology. However, the degree of such needs varied, and the S1. AV Fixed-Route Transit Service_BRT, where the level of infrastructure maintenance was generally high, showed a high need only for the fundamental technologies necessary for longitudinal and lateral control. The result of the expert survey shows a high need for cloud-related technologies that are closely related to the efficiency in the operation of public transportation among the autonomous driving-related infrastructure technologies for the whole service field. The AV On-Demand Transit Service and the AV Paratransit Service, which particularly needed to manage the schedules and operate vehicles dynamically, showed the highest need for cloud technology. For the technologies related to driving assistance, mobility, and safety, there is a high need for a digital road sign technology that is closely related to the static map and technologies closely related to the dynamic map such as information provisions for lane-based traffic, signals, and accidents. There is a relatively low need for external information-based control and warning related technologies in comparison to other infrastructure technologies. However, there is a high need for a waiting line warning in comparison to other services. This is because the position of a waiting line significantly affects the safety of autonomous driving.
3) Autonomous driving-based public transportation service introduction strategies
The introduction strategy for each service was drawn by evaluating the driving suitability of current public transportation-related road infrastructure. The evaluation comprised the driving test and its comparison with the necessary infrastructure technology level for supporting autonomous driving for each service drawn earlier. It is expected that it is possible to introduce autonomous driving based on ‘vision sensor + deep learning + radar sensor’ without significant improvement of the existing infrastructure for the ‘S1. BRT’ Service and the ‘S2. Branch line’ Service. Both service types show relatively high driving suitability of the current infrastructure and the low infrastructure technology level necessary for supporting autonomous driving. In the case of the ‘S3. Group’ Service and the ‘S4. By-Pass’ Service, both show moderate driving suitability of the current infrastructure and the moderate infrastructure technology level necessary for supporting autonomous driving. For these services, the possible development of the optimization solution is expected by considering the improvement of the physical infrastructure as well as the provision of active safety support service through the establishment of the necessary digital infrastructure and C-ITS such as a highly precise map. The ‘S5. Downtown Area’ Service and the ‘S6. Deprived Area’ Service showed low driving suitability of the current infrastructure and the high infrastructure technology level necessary for supporting autonomous driving. For these services, the possible introduction of an autonomous driving vehicle-based service is expected only when it is accompanied by measures for various factors, including poor marking status, illegal vehicle parking and stopping, sharp curves in roads with a narrow width, obstacles and pedestrians, and speed bumps. In particular, the local load where the ‘S6. Deprived Area’ Service is provided shows very low autonomous driving suitability of the road. Therefore, it is considered that taking a strategy to establish digital infrastructure based on main routes would be advantageous for fast commercialization.
4) Conception of autonomous driving-based public transportation system
In comparison to the current public transportation system, it is expected that the town bus among the inter-city and transit bus, feeder bus, and the town bus included in the current public transportation system, will be converted into the demand bus for improving efficiency and travel convenience. It is expected that the fixed operation method and fare system will be maintained for the inter-city and transit bus and the feeder bus even if the autonomous driving service is provided. Of course, the autonomous driving technology can be introduced faster for a section where the infrastructure environment is already prepared such as the BRT system. However, as there is a high traffic demand as well as clear peak and non-peak traffic patterns, such a service will be switched to a fully autonomous service based on the means of transportation in the method to reinforce the safety rather than the efficiency in the operation.
The most significant change in the semi-public transportation system is the chartered bus. Generally, chartered buses are commuting buses, such as shuttle buses or tour buses, for certain private companies. It is expected that the operation method and fare system for such bus services will be switched to the complete demand responsive operation method and fare system. The previous demand responsive operation method and the flexible fare system for carpool, taxi, and sharing-based taxi services will be maintained. However, it should be noted that various business models and operators will emerge for the operation of such services according to the provision, operation, and management of autonomous driving services as well as the operation and management of sharing services.
Domestic public transportation is one of the key traffic policy fields in the country. A change in the autonomous driving-based smart public transportation system is significant for the support of transportation innovation in the era of the 4th Industrial Revolution. It is expected that the comparative analysis of the infrastructure level, service introduction strategies, and conception of the future public transportation system based on the analysis of actual autonomous driving-related vehicle and infrastructure technologies will serve as the fundamental research for the establishment of public transportation policies in the future. In this regard, the establishment of R&D plans for key technologies for supporting public transportation, development of policies, and the amendment of laws and regulations that support such plans should be carried out in connection with the result of this study. Moreover, it is necessary to promote commercialization through the integration of technology development and service application.