Identifying key elements in a car-sharing system for constructing a comprehensive car-sharing model

Abstract

Car-sharing aims to reduce energy consumption by making the best use of carrying capacity of a car. Nevertheless, like any new things, it does not go on quite smoothly. Passengers may not be willing to participate in a car-sharing system (CSS), with consideration of safety, convenience, privacy, and so on. To solve these problems, key elements in CSS are identified, and a comprehensive car-sharing model is established. Finally, the design process of CSS is proposed with four steps: identification of user requirements, service development, optimization & feedback, and verification.

Keywords

Car-sharing system key elements user requirements willingness to participate shared cars

1 Introduction

Cars bring great convenience to people’s daily lives and extend their ranges of activities to a great extent. According to official statistics delivered by Traffic Management Bureau of the Ministry of Public Security of China, until the end of 2018, total vehicle ownership in China was up to 325 million, among which 240 million was automobiles and it took up 73.8% of total vehicle ownership. The amount of privately registered cars was 187 million, taking up 77.9% of the total registered automobiles. Averagely, there are more than 40 private cars per 100 households and it may exceed 70 in those more developed urban cities. Figure 1 shows the registered amount of private cars in China mainland from 2012 to 2018. It is clearly revealed that the registered amount of private cars in China mainland keeps on increasing steadily.

Fig. 1

Registered private cars in china mainland from 2012 to 2018.

Despite this, it cannot be denied that cars are actually two-edged swords. With the ever-increasing amount of private cars, the environment is getting worse and worse, resulting in global warming, more energy consumption, exhaust gas emission, traffic accidents, and traffic jams. It is revealed that for most European private cars, 92% of their lives are wasted on parking without any motion, 1% is stuck in traffic jam, 1.6% is looking for a parking space, with only 5% driving on road, and averagely carries only 1.5 passengers including the driver [1], as demonstrated in Fig. 2.

Fig. 2

Improper use of private cars.

Generally speaking, there are two kinds of car-sharing service [2]: business to customer (B2C) and customer to customer (C2C). Periodic lease is most frequently used in a B2C car-sharing system (CSS). Users locate and unlock a car by mobile applications and pay according to actual driving distance or time. In a C2C car-sharing service mode, a third-party service provider establishes a platform to deliver information to car owners and users, making the best use of vacant seats of a car by carrying more passengers [3].

The rest of this paper is organized as follows: research question and theoretical bases are discussed in Section 2; Key elements in a car-sharing system are identified in Section 3, which are divided into two categories: hardware elements and software elements. And the latter category includes three kinds of elements, i.e., economic, social, and technical elements respectively. On the basis of Section 3, a comprehensive CSS model is established in Section 4. And design process of CSS is proposed in Section 5. There are four steps in it: the first step is identification of user requirements; the second step is service development; the third step is optimization & feedback, and the last step is verification. Section 6 offers some discussions and conclusions.

2 Research question and theoretical basis

2.1 Research question

A successful operation of CSS calls for the collaboration of different stakeholders including governmental institutions such as branches of traffic administration, and environmental protection, CSS providers, automobile owners, drivers, and passengers etc. It is a challenging task to balance the interests of all stakeholders, to attract more users to participate in CSS, and to achieve a sustainable mobility mode for mutual benefit. Therefore, it is of great significance to identify key elements in CSS and establish a CSS model, which is the basis of CSS comprehensive evaluation.

To design a successful CSS, it is necessary to identify key elements, and develop a car-sharing service accordingly [4]. User requirement (UR) identification, optimization, feedback, iteration, and verification are all necessary to find possible problems at the design stage of CSS, to ensure a successful operation of CSS, to achieve positive economic profit, to reduce energy consumption and emission of gaseous pollutants, and to ensure social equity eventually. It is the motivation of this research to identify key elements in a car-sharing system, and to propose a comprehensive car-sharing model, which may be helpful for comprehending CSS better.

2.2 Theoretical basis

This study was based on the theory of planned behavior (TPB), which was proposed and developed by Icek Ajzen [5]. TPB is helpful in comprehending the mechanism of human behavior and widely applied to predict user behavior. Main ideas of TPB are listed as follows: 1) Intention has an obvious effect on behavior. What’s more, other elements also restrict behavior, i.e., personal capability, opportunities, and resources; 2) The probability of behavior occurrence can be inferred by perceptual behavior, and the authenticity of perceptual behavior control determines the accuracy of prediction; 3) Variables that play a decisive role in behavioral intention include individual’s subjective attitude, behavioral norms and perceptual behavior; 4) Under certain conditions, a small number of beliefs that can be acquired are called salient beliefs, and they are the bases of subjective attitudes, behavioral norms and perceptual behavior; 5) Age, gender, personality, intelligence, experience and other social elements may have an impact on behavioral beliefs, and indirectly affect behavioral intentions [6].

3 Identification of key elements in a car-sharing system

The debate over car-sharing and car-owning is always a hot issue these years. Scholars have conducted a lot of research on car-sharing system. [7] proposed a game-theoretic model to study the key factors in car-sharing and its way of reducing environmental impact. They revealed a fact that car-sharing is capable of making profit while reducing urban congestion. [8] developed a model to know more about user perceptions and service quality, aiming to find out the role of service quality, service loyalty, and sustainable mobility in users’ participating of CSS. Their research revealed the importance of service quality in the success of CSS. [9] adopted a life cycle assessment perspective and proposed a framework to assess life cycle impact of CSS, which is useful to evaluate environmental life cycle impact. [10] proposed a model to study car-sharing services in the Netherlands, with a multilevel perspective, demonstrating the relation between mobility innovation and adoption of CSS. We did not identify much literature on key elements in a car-sharing system. That is why we conduct this research.

CSS is a complicated and dynamic system, including many key elements and sub-elements. We clarify key elements in a car-sharing service system into hardware and software elements, and software elements refer to economic, social, and technical elements. Shared cars and shared parking spaces are the physical foundations of CSS, and they are named as hardware elements in this study.

As far as hardware elements are concerned, we attribute shared cars and shared parking space into this category. On the one hand, in a traditional B2C CSS, car-sharing service providers usually spend huge amount of money in purchasing cars. Nowadays, many traditional automobile manufacturers are transforming their production mode to shared cars, providing specially designed cars for the purpose of sharing. By contrast, a C2C CSS is more flexible, which calls for the participation of private cars and makes advantage of vacant seats, satisfying more mobility requirements by dynamic ride-sharing. On the other hand, with the steady increase of private cars, parking space is becoming a valuable resource. It is hard to find a parking space, which is a widely recognized social problem. Sharing the parking spaces with others would be of great significance and bring new ideas for parking in an era of sharing economy. For example, when you drive to workplace during daytime, other people can park their car in your parking space and vice versa.

When it comes to software elements, there are three kinds of elements in this category, i.e., economic elements, social elements and technical elements. First and foremost, economic elements include profit mode, state of operation, and travel cost. Profit mode and state of operation are proposed from the perspective of car-sharing service providers, with consideration of economic profit that car-sharing may bring to them; travel cost is proposed from the perspective of passengers, with user experience and willingness to participate (WTP) being the main elements that a passenger may consider while using car-sharing service. Secondly, social elements include UR, user’ WTP, safety, and policies. Users’ mobility requirements are dynamic and multiplex. It may be decisive to acquire users’ travel information for the success of CSS. Users’ WTP in CSS is the foundation of CSS. Only those positive experiences can improve users’ WTP, and promote a healthy development of CSS. Last but not the least, technical elements of CSS include interface, cloud service platform and so on. A user-friendly interface and reliable service platform are key technical elements of CSS.

3.1 Hardware elements

3.1.1 Shared cars

It is the value proposition of CSS to improve the efficiency of cars by sharing with others, to reduce empty-loaded rate and waste of energy. Shared cars mean that many people share a car without property, and they only use the car in a given period of time. By means of sharing, we do not need to spend much money on a car, and there is no need to worry about insurance, maintenance, and annual vehicle check [11]. What users only need to do is to release a service requirement through a mobile application, and the system will search for a nearby car automatically.

New energy vehicles (NEV) [12]are powered by unconventional fuels, including pure electric vehicles, hybrid electric vehicles and other new energy vehicles. NEV plays a dominant role in today’s car-sharing market, which is widely applied by most of the car-sharing service providers. This kind of condition is closely related to China’s national subsidy policy. To make NEV widely accepted by the public, a special fund is allocated from central budget to support NEV, and local government usually subsidizes 50% more of central subsidy. At the same time, it cannot be denied that NEV are also restricted by many elements, to name a few, the low acceptance rate, incomplete supporting facilities, high maintenance cost, limited public awareness of environmental protection and so forth. Besides, NEV must solve the following problems: limited endurance mileage, improper location of charging piles, limited power and speed.

Periodic lease is widely adopted in China’s car-sharing market. Users may reserve, locate, and unlock a car by their mobile phones, and pay according to actual driving distance and time. To make it serve the purpose of car-sharing better, the design of shared cars should follow the principle of “economic and functional”. It would be better if it is compact and easy to park while satisfying the need for car-sharing. What’s more, shared cars should be flexible and durable, decorated with bright colors or symbols in order to be recognized easily. Due to the lack of property, users may drive carelessly. Therefore, how to improve safety and reliability of shared cars is an urgent problem.

Besides NEV, many private cars also participate in car-sharing actively. Asset-light strategy is adopted by C2C car-sharing service providers [13], which means that CSS providers do not need to purchase so many cars, making the best use of private cars by providing information of vacant cars, and travel requirements and match drivers and passengers.

Users may choose to drive a shared car themselves or choose a car that is driven by others. The price of car-sharing is determined by different vehicle conditions, driving modes, time and distances. Usually the car-sharing system calculates a price automatically, for users’ reference when they order a car. Due to the special characteristics of a car, there may be unexpected accidents during the usage of shared cars. Car-sharing service providers need to check the registered users very carefully, including their drivers’ license and driving histories to ensure that they will never drive after drinking alcohol, taking drugs, or drive dangerously. The mode of sharing a private car and that of periodic lease for NEV is quite different. Car-owners are responsible for the maintenance of their vehicles. Private car owners may sometimes claim a mobility demand for themselves and they are willing to share their car with others only when it is not used by the car owners. Therefore, this kind of car-sharing is more complicated and flexible.

3.1.2 Shared parking space

For a shared travel, the importance of a shared parking space is no less than a shared car [14]. In fact, in an urban core area where land is scarce, with the continuous increase of motor vehicles, the pace of construction of related supporting facilities is lagging far behind, resulting in widely recognized difficulties of parking [15]. Taking Guangzhou as an example, the ratio of motor vehicles to parking spaces is 10 : 3, and it is quite difficult to park, especially in downtown areas and during rush hours. Most of the existing car-sharing service providers sign parking space agreements with the property management companies in the form of monthly rental, and there are the following problems: Firstly, users’ destinations are usually far away from the appointed parking spaces, resulting in great inconvenience. Secondly, for those reserved parking spaces, they are unable to provide services for other people with parking demand when they are vacant, resulting in a great waste of resources. An optimized CSS design advocates sharing their parking spaces, to better solve the parking problem. How to share parking information with users is a key issue in sharing of parking spaces.

There are two kinds of services for parking spaces sharing: sharing by staggered time (SST) and sharing by staggered place (SSP). SST advocates sharing parking spaces by different time periods to serve different users. For instance, a whole day may be divided into day parking and night parking, or a week may be divided into workday parking and non-workday parking. In this way, parking spaces near some office buildings can meet the parking demands of the staff during working hours; while during non-working hours, it is provided to nearby residents. SSP is different from SST, and it advocates sharing parking spaces according to their service ranges. There are two kinds of SSP: The first one is to share the discrete and separate parking spaces in some specific areas, making full use of limited resources, and meeting the parking demands better in this area. The second one refers to the sharing of parking spaces among different areas. As is well known, in the face of the very huge contradiction between limited parking spaces and tremendous parking demands, it is helpless only by raising the parking fee. Administrators should propose more practical and effective measures to expand parking lots, to promote three-dimensional parking spaces and to increase roadside parking spaces. Even so, with the ever-increasing number of vehicles, the construction of parking spaces is lagged behind. In the era of sharing economy [16], exploring the sharing of parking spaces is expected to alleviate the problem of parking difficulty to some extent, and there are a lot of measures to be adopted, such as opening free parking spaces in residential areas to nearby office workers and sharing the company parking spaces with nearby residents.

3.2 Economic elements

3.2.1 Profit mode

Whether CSS can make profit or not and how to make profit are what CSS providers concern most. Firstly, it is very important to choose a proper operational mode. In actual operation of periodic lease, construction of infrastructures like parking spaces is important. Therefore, how to balance the interests of stakeholders and allocate resources reasonably is a decisive factor that determines a CSS provider’ s profit. Secondly, periodic lease of cars calls for moderate-sized stock of vehicles and stations. The reasonable choice of vehicle scale and station density is directly related to the interests of consumers and economic benefits of enterprises. Thirdly, as more and more enterprises participate in car-sharing, to stand out in the fierce market competition, they are supposed to design a flexible CSS operational mode, reasonable charging method and to provide qualified service.

There are many stakeholders in the operation process of CSS, among which government administrators, CSS providers, and investment companies are the most indispensable three. In the car-sharing market in China mainland, there are five kinds of modes as follows: round-way, one-way, C2C, drive-for-you, and ride-sharing [17]. Characteristics and limitations of each mode are listed in Table 1.

Table 1
Main CSS modes in China mainland

Modes Source of automobiles Characteristics Limitations

Round-way Self-owned/rented Pick up location ¬= drop off location Relocation need

One-way Self-owned/rented Pick up location = drop off location Not flexible

C2C Private cars Inexpensive, widespread Law/integrity

Drive-for-you Self-owned/rented/private Convenient Safety/law

Ride-sharing Self-owned/rented/private Inexpensive Safety/law

Modes	Source of automobiles	Characteristics	Limitations
Round-way	Self-owned/rented	Pick up location ¬= drop off location	Relocation need
One-way	Self-owned/rented	Pick up location = drop off location	Not flexible
C2C	Private cars	Inexpensive, widespread	Law/integrity
Drive-for-you	Self-owned/rented/private	Convenient	Safety/law
Ride-sharing	Self-owned/rented/private	Inexpensive	Safety/law

Users are required to register first to participate in car-sharing, fill out personal information, upload a photo of driver's license and pay a certain amount of cash pledge. If there is no accident, they can claim back the cash pledge after the order is finished. On the one hand, for car-sharing providers, cash pledge is a good way to reduce the risk of shared cars. On the other hand, for users, paying cash pledge is a high-risk mode due to lack of effective administration. The claim back of cash pledge usually needs to wait for a long time. Many bike-sharing companies in China mainland have broken down, and the majority of users failed to claim their money back. This kind of condition makes it even difficult for users to pay pledge for car-sharing services. Besides, different car-sharing providers usually use different mobile applications. And if users want to enjoy car-sharing service provided by different companies, they must register and pay cash pledges for different car-sharing companies, restricting the flexibility of users to a great extent.

Taking periodic lease as an example, cost and benefit modes of CSS are analyzed as follows. The cost of periodic lease of a car includes the following items: 1) Fixed costs related to vehicle purchase and insurance, accounting for about 70% of the total single-day cost. The fixed cost of NEV is lower than that of gasoline vehicles due to the subsidies from the state and local governments. However, if there are enough NEV vehicles, the subsidies are bound to be reduced. 2) Parking cost, that is, the cost of buying or renting parking lots, and parking cost is relatively stable. Different time sharing modes may result in different parking costs. For example, in the lease mode of free pickup and re-delivery, users may park the vehicles in any parking spaces, and the parking cost is divided into two parts: the user shall bear the parking fee before re-delivery, and the next user shall bear the parking fee after re-delivery. Averagely, parking costs account for about 11% of the total cost of car-sharing. 3) Operational cost, and it mainly includes vehicle scheduling cost, vehicle maintenance cost, etc., and operational cost accounts for about 8% of the total cost. 4) Energy cost, refers to the cost of energy consumption of the vehicle, such as charging or refueling. Energy cost accounts for about 11% of total cost. The income for time-sharing car rental service includes the rental income of the vehicle and the income from the later disposal of the vehicle, and the latter fits only for the company’s self-owned vehicles. Rental income is in direct proportion to the actual use time of the vehicle. Relevant data include: daily order quantity, mileage per order, average use time per order, etc. Vehicle disposal income refers to the residual value of the vehicle when it no longer meets the requirements of car-sharing lease as the vehicle grows older. As for electric vehicles, components such as batteries and motors are vulnerable, and the residual value of electric vehicles is generally low, which is at most 20% of the value of new cars.

3.2.2 State of operation

At the beginning stage of Chinese car-sharing companies, great amount of money was spent in order to cultivate market and attract users. It was quite unimaginable that you may earn some money if you use a car-sharing service at that time because car-sharing companies subsidized madly, both to passengers and drivers. After that, some companies cannot sustain the competition and broke down or was merged. And many users chose to quit car-sharing without the promised discounts that they used to enjoy. For those survived companies, they find it hard to make profit and they need to deal with many unimaginable difficulties. To name a few, unstable sharing platform, lack of efficient administration, and lack of safety. All of these problems are all difficult to solve. Without a healthy, stable, and sustainable profit mode, the future of car-sharing is not worthy of expecting. To make profit, the most important is to improve administration and service quality.

3.2.3 Travel cost

The main reason for users to participate in car-sharing may be attributed to its low travel cost. For passengers in car-sharing services, there are two kinds of travel cost: time cost and economic cost. Time cost is related to the quick response of CSS while economic cost is related to the money they need to spend for a shared mobility demand. Reduction of users’ travel cost may reduce the profit of a car-sharing service providers, and makes it difficult to sustain in car-sharing services but in no case should users’ travel experience be sacrificed. Poor experiences may prevent users from accepting CSS. Therefore, travel cost is a very important element in CSS design and evaluation.

3.3 Social elements

3.3.1 User requirements

UR is the starting point of any product or service. The original intention of CSS is to serve uses’ flexible and dynamic mobility needs without purchasing new cars. However, it is a challenging task to acquire users’ travel information. For a particular mobility demand, there is not only appointed departing place and destination, but also expected departing and arrival time. The more restrictions of a user requirement, the more difficult it is to be satisfied.

The method of design thinking proposed by Stanford University advocates solving problems by means of design thinking. There are five steps in this method: empathize, define, ideate, prototype, and test. First and foremost, empathy means that designers need to feel as users do. It is no easy job to feel and experience like others. An excellent designer should give up any prejudices, and look at things in a totally new way, with a perspective of the targeted users. Careful observation may be the beginning of empathetic experience. Designers are supposed to observe users without being noticed during their actual daily lives. It is noteworthy that users’ words may not match their actions. Therefore, it is necessary to find out the true reasons behind. After careful observations, designers may know better of users, and sometimes they need to interview with users to figure out their potential requirements.

3.3.2 Willingness to participate

The success of CSS is related to stakeholders’ WTP to a great extent. Stakeholders refer to CSS providers, car owners, and passengers [18]. Different stakeholders may have different interests. CSS providers care more about the profit capability and economic performance; car owners pay more attention to the proper use of their cars; and passengers’ attitudes towards CSS may be influenced by the following elements: age, gender, income, educational background, family, travel distance, travel cost, traffic jam, parking difficulties, privacy, and safety. Based on TPB, a model of willingness to accept car-sharing is established, as shown in Fig. 3.

Fig. 3

Willingness to participate in car-sharing based on theory of planned behavior.

3.3.3 Safety

Security problems in CSS mainly come from two aspects: one is the safety of users in the process of sharing; the other is the safety of the vehicle itself. There are many factors that attract users to use shared cars, such as economy, efficiency and convenience. But in the process of car-sharing, ensuring the safety of the user’s lives and properties is the most important issue. In recent years, it is not uncommon to see extreme violent incidents. For example, car owners are robbed; and passengers may drive shared cars violently, which affects the willingness of users to participate in sharing and thus restricts the healthy development of car-sharing. If safety is not guaranteed, people will not take risk to use shared cars. The importance of safety can never be overemphasized and safety is a major problem that plagues car-sharing. Car-sharing service providers should take effective measures to ensure the safety of their vehicles, such as strict examination, enhanced supervision and necessary insurance.

Shared cars faces two major safety problems: theft and damage. A Global Positioning System (GPS) is usually installed in a shared car, yet the locations of GPS in some vehicles are too obvious and vulnerable. The design of shared cars should be improved to reduce the risk of theft and robbery to a certain extent. There is also some risk of malicious damage to vehicles, either by commercial competitors or other stakeholders. When their own interests are damaged, they will do everything they can to destroy shared cars. We can apply face recognition or user rating to supervise and improve the threshold for users with poor rating. During the process of car-sharing, service providers may face safety problems such as scratches, illegal parking and traffic accidents, and it is why the majority of car-sharing platforms to require registered users to pay a cash pledge. Once such problems occur, there may be buck-passing, and it is difficult to identify the responsibility. Therefore, CSS designers should take the potential security risks into account. No matter whom the vehicle is rented to, in case of an accident, the CSS platform should always be reliable. It is noteworthy that there is a disclaimer clause in most car-sharing Apps: “no warranty is made on the car, including default or warranty on the suitability or goodness of the car. If a user feels that the vehicle may not be safe, they should stop using it and contact customer service immediately.” Obviously, such regulations are not reasonable. It goes without denying that car-sharing platforms are responsible for safety.

As for the safety of shared cars, the following suggestions may be proposed: firstly, governmental administrators should strengthen the supervision of shared platforms, including their business qualifications and vehicle conditions. Secondly, CSS providers should strengthen the supervision of drivers, including comprehensive consideration of their driving records, and share information with other sharing platforms. Finally, risks that may be faced during CSS operation can be shared by purchasing compulsory traffic insurance and commercial insurance.

3.3.4 Policies

Car sharing is bound to encounter various problems during its development, to name a few, shared cars were boycotted jointly by taxi drivers, and were reported as “illegal car”. If relevant laws, regulations, and policies cannot keep pace with the development of car-sharing, it will inevitably perform poorly. Regulations in car-sharing are inadequate. Car-sharing is in urgent need of supporting policies. Governments and functional branches at all levels should issue corresponding policies on market access, vehicle status, insurance and other issues to ensure a healthy environment for car sharing.

According to “interim measures for the administration of online car-sharing services” issued by Ministry of Transport of the People’s Republic of China, qualified vehicles for the car-sharing service should be passenger vehicles within 7 seats, meeting the operational safety standards, installed with GPS devices, and the vehicle is reserved for passenger transportation, with a service life within 8 years. After changing the nature of private cars into commercial vehicles, the service life of private cars will be shortened to 8 years, which will restrict private cars from entering the car-sharing service platform. Since 2016, cities such as Beijing, Shanghai, Guangzhou and Shenzhen have released draft rules for online car-sharing and ask for comments. In big cities such as Beijing and Shanghai, it is required that shared cars should have local license plates and drivers should have local residence permit. According to “Beijing network car-sharing service management implementation rules”, the operational period of a car-sharing platform is 4 years, and the application for extension can be applied only if the platform is qualified for the check; a car-sharing platform shall assume relevant legal responsibilities, such as carrier responsibility, safety responsibility, management responsibility, and relevant insurances. Due to safety and management considerations, the above regulations impose many restrictions on the vehicles to be shared. In the future, more flexible policies and regulations should be applied to car-sharing services.

NEV sharing is a kind of car rental. Currently, there are no laws and regulations at the national, provincial or municipal levels. Therefore, relevant problems in the usage of shared NEV vehicles are still in a legal blind state. In order to ensure a healthy development of car-sharing system and to promote CSS towards a better future, relevant laws and regulations should be enacted as soon as possible.

3.4 Technical elements

3.4.1 Interface

CSS is completed through a series of actions from reservation, pickup to return by APP. Therefore, the design of human-computer interface is very important. Whether the interface is simple and easy to operate will directly affect user experience and has an important impact on their willingness to participate in the future. When users participate in shared service, they are interacting with the system. At this time, user’s feeling is an important interactive experience. The purpose of interaction is to make CSS more user-friendly, easy to use, and it is necessary to understand the expectation, psychology and behavior characteristics of participators. For the design of CSS interface, a connection between CSS system and users should be established. The interaction process should provide timely feedback and useful information to meet users’ expectations, reduce possible anxiety caused by uncertainty in the process, and improve their positive experience effectively.

3.4.2 Service platform

Service platform is the core of CSS and its design is directly related to the operational capability of the system. Based on advanced technologies such as internet of things [19], cloud computing [20], mobile internet [21] and big data [22], and with the help of operational research algorithm, car sharing service platform is developed to efficiently integrate resources such as vehicles, and parking spaces, and to realize basic functions such as vehicle control, time-sharing lease, smart parking, information transmission, management and monitoring. With a mobile phone, users can easily enjoy car-sharing services. By changing consumers’ habits, cloud service platform weakens their willingness to purchase cars and promotes the popularization of car sharing.

Generally speaking, CSS cloud platform includes the following modules: member, vehicle, APP, customer service, and management system, etc. Its technical architecture can be divided into four layers, namely client layer, scheduling layer, business layer and data layer. Client layer includes membership system, APP, customer service system and management system; scheduling layer processes user requests from the client layer and schedules them according to different business types; business layer executes the business logic and processes the requests of the scheduling layer; and data layer is mainly responsible for database management, including file addition and deletion, modification, query, input & output, and so on. Fig. 4 is a CSS operational system.

Fig. 4

CSS operational system.

A comprehensive CSS evaluation calls for the consideration of key elements from economic, environmental, systematic, and social dimensions. The identification of key elements in CSS is quite important in order to establish a comprehensive evaluation indicator system for CSS, to determine indicator weights and to construct a comprehensive CSS evaluation model. Hardware elements, shared cars and shared parking spaces are material bases of a CSS. Profit mode, state of operation, and travel cost are closely related to economic performance of CSS. UR, users’ WTP, safety, and policies determine the performance of CSS in social dimension. Interface and cloud service platforms provide technical support for the operation of CSS.

4 A Comprehensive CSS model

Based on the above-mentioned elements, a comprehensive car-sharing model is proposed, as shown in Fig. 5. CSS model is the object of CSS evaluation, revealing the above key elements and four dimensions, i.e., economic, environmental, systematic, and social. Shared cars and shared parking spaces are hardware elements, which influence the economic, environmental, systematic, and social performances directly. Economic elements are the key of CSS operation, including profit mode, state of operation, and travel cost. Social elements refer to UR, users’ WTP, safety, and policies. Technical elements include interface, and cloud service platforms.

Fig. 5

A comprehensive car-sharing model.

UR is the starting point of CSS, and satisfaction of users’ mobility requirements is the final purpose of CSS. If a CSS is widely accepted by users, it may bring positive economic, environmental, and social effects as well. Interface and cloud service platforms are decisive factors in CSS operation. And profit mode is directly related to its systematic performance. All the above-mentioned elements influence one another, and they are indispensable for constructing a CSS model.

5 Design process of CSS

To carry out CSS evaluation, it is necessary to understand CSS design process, to grasp the problems that may be encountered in CSS design process from the stages of demand identification, service development, design optimization, feedback and verification. Evaluation experts should think about the application of CSS evaluation in CSS design and apply the results of CSS evaluation to guide CSS design, and put forward more feasible CSS options.

Design initiates from user requirements, and the design of CSS initiates from users’ mobility requirements. We develop CSS prototype system according to user requirements, design optimization and feedback. In CSS design process, firstly, we need to determine functional characteristics of car-sharing according to different user needs; secondly, functional characteristics are transformed into the characteristics of design scheme of car-sharing to form a scheme set. Finally, the optimal scheme is selected from the scheme set, and the specific design parameters are given accordingly.

5.1 Identification of UR

CSS user is a broad concept, including not only drivers, but also service providers, car owners and other stakeholders. Depending on actual needs of a user, he/she may drive the vehicle by himself/herself or some driver may drive for him/her, and there will be a driver involved in the latter case. The main goal of CSS is to meet the needs of users by means of sharing. However, the actual travel demands are restricted by many factors and there is great uncertainty. Sometimes, you can determine the travel plan in advance, but sometimes, it is hard for you to plan until the last minute, leaving departure place, departure time, destination and expected arrival time unknown. Therefore, it is a great challenge in the process of CSS design and implementation to identify the actual needs of users accurately and responds quickly. Figure 6 shows the path diagram obtained by user requirements [23]. According to the explicit or implicit features of knowledge, information such as what users say, what they think, what they do, what they use, what they know, what they feel and even what they dream can be acquired through interview, observation, conversation and other methods, in order to comprehend user demands of CSS better.

Fig. 6

Acquisition of UR.

To acquire user’ travel requirements in a CSS, the following steps may be followed:

First of all, proper methods are selected to obtain stakeholders’ requirements, including passengers’ mobility demands, service providers’ profit, administrative demands, and the maintenance cost of vehicles.

Secondly, activities that must be conducted to acquire the above-mentioned requirements are identified;

Thirdly, weights for different requirements are settled by means of Delphi.

5.2 Service development

On the basis of UR identification, we transfer UR to design requirements, and work out different car-sharing options, then we evaluate each of these options and choose the best one. Due to the flexibility and diversity of UR, car-sharing service developers should give enough consideration to the interests of different stakeholders, and balance the dimensions of economic, environmental, systematic, and social, in order to propose different car-sharing service options.

CSS consists of shared cars, services, infrastructures, and network, with an aim to satisfy more mobility demands by means of car-sharing. Shared cars are the physical basis of CSS, which may be owned by service providers or the public. Vehicles should be in good condition to ensure safety. Service quality is decisive for the success of CSS and every touch point should be given enough consideration to ensure a pleasant and positive experience. Only in this way, should users’ requirements be satisfied. For a particular CSS, infrastructures mainly refer to parking places. And car-sharing providers usually offer special parking places for users and it is rather easy to park a shared car. Network is a necessary means for the smooth operation of CSS since passengers order, reserve, or unlock a car by means of network. All the above-mentioned elements are related and indispensable to one another.

5.3 Optimization & feedback

After the CSS option set is established, optimization and feedback need to be carried out by simulation and iteration. CSS comprehensive evaluation technologies are used to assess different options and determine the best one to achieve the balance of interests of all stakeholders. The evaluation process must comprehensively reflect the interests of all parties. Only by realizing a win-win situation of CSS, can the system operate healthily and continuously.

According to the result of CSS comprehensive evaluation, CSS design is optimized and fed back. Due to the personalized, diversified and dynamic characteristics of travel demands, there are different correlations between travel demands and service characteristics. At the optimization and feedback stage, not only the importance of service characteristics should be considered, but also the possible influence of energy utilization, travel cost, sustainability and other factors should be taken into account to meet as many travel needs as possible at a relatively low cost.

5.4 Verification

The reliability and robustness of the car-sharing service can be verified by establishing prototypes. According to the evaluation results, the process tools and control plan of CSS are developed, so that the whole system can meet the needs of users in a sustainable way and respond sensitively to the changing needs at any time. After trial operation and application verification, the possible problems at the design stage are expected to be found out, a comprehensive operation of the system is verified, and user experience information is obtained, so as to avoid losses that may be caused by design mistakes. The validation phase plays an important role in keeping CSS running well. Figure 7 shows the flow chart for CSS design.

Fig. 7

Design process of CSS.

The CSS design process consists of four phases: requirements identification, service development, optimization & feedback, and validation. Firstly, CSS requirement identification includes three steps: CSS requirement description, CSS requirements acquisition and weight determination. Through the task analysis of CSS, the demand description information of each stakeholder is obtained, which is processed and extracted to obtain the accurate information of user demands, and the method of Fuzzy Analytic Hierarchy Process [24] is applied to determine weights of user demands. Secondly, service development phase consists of two steps: CSS service functional planning and CSS service functional characteristics. Through the transmission and mapping of CSS requirements, important information of functional features of CSS products, product option features, service functional features and service scheme features are obtained, providing important references for service development. Thirdly, at the optimization and feedback stage, based on the work in the previous two steps, car sharing service scheme is generated, involving two major modules, i.e., product and service, to determine the characteristics of CSS service and optimize the car sharing options. Finally, through small-scale operation and verification, the proposed CSS can be verified and improved according to the feedback.

6 Discussions and conclusions

Key elements of CSS are analyzed, including hardware and software elements. Hardware elements include shared cars and shared parking spaces, which are the material bases of CSS implementation. How to make the most advantage of shared cars and parking spaces to meet the needs of society with limited resources is an important issue in the era of sharing economy. Software elements include economic elements, social elements and technical elements, etc. The economic elements of CSS include profit mode, state of operation, and travel cost, etc. The profit mode is related to the interests of CSS operators, and benefits ordinary users. State of operation and travel costs are the focus of the operators and users, respectively. Social elements include user requirements, WTP, safety, policies and regulations, etc. Only by attracting as many users as possible to participate in car-sharing, can CSS make profit and show its advantages in dimensions of economy, environment and society. UR is fundamental, and WTP is the key of car-sharing service.CSS security factor is crucial, which cannot be ignored; policies and regulations ensure that car sharing develops in a healthy way. Technical elements include interface, and service platform, etc. Interface design directly affects user experience to some extent, and then urges them to make a decision whether to participate in CSS or not. And cloud service platform is the core of CSS.

Key elements of CSS are clarified, and the design process of CSS is elaborated, with four steps: requirement identification, service development, design optimization & feedback, and verification. A four-dimensional comprehensive CSS model was constructed, including dimensions of economic, environmental, systematic and social, to clarify the characteristics of the research object and to lay a foundation for the comprehensive evaluation of CSS.

Despite of the above-mentioned advantages, there are some limitations of this research. Firstly, the key elements listed in this work may not be comprehensive enough and some other elements still call for future work. Secondly, the authors divided all the key elements into four dimensions, and they are economic, environmental, systematic, and social dimensions. These dimensions may not be typical and representative enough. Thirdly, we did not compare the proposed key elements with other research and previous contributions. Last but not the least, this work is mainly qualitative analyses without rigorous mathematical proof or data analysis. And all these limitations need to be improved in future research.

Footnotes

Acknowledgments

This study was funded by Teaching Reform Project for Universities and Colleges in Jiangxi Province (Grant No. JXJG-18-1-13), Key Research Base of Humanities and Social Sciences in Universities in Jiangxi Province (JD17115) and Cultural and Artistic Planning Project in Jiangxi Province (YG2018170). The authors would also like to thank the anonymous referees for their constructive comments.

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