Transportation Deployment Casebook/2018/Nanjing Metro (2005-2017)

The Introduction of Nanjing MetroEdit

Nanjing, which is also called as Jinling, it is the capital city of Jiangsu and the second largest city in East China, locating in the lower reaches of the Yangtze River and southwestern Jiangsu. In addition, it is also an essentially political, economic, scientific, educational center in Jiangsu Province [1]. With the development of technology and society, Nanjing is one of six cities in China, which have subways, involving Beijing, Shanghai, Guangzhou, Shenzhen and Tianjin.

Its total length of metro system (347 km) ranks fourth in China, only after Shanghai, Beijing and Guangzhou; and the 1st line of Nanjing metro system was officially opened on 15th May 2005, and government encouraged to extend the metro system network; According to the database collected by Travel China Guide, it indicates that Nanjing metro system currently has 9 metro lines in service, such as line 1, 2, 3, 4, 10, S1, S3, S8 and S9 with 164 stations running on 347 km of track [2]. As for these lines, line 1, 2, 3, 4 and 10 could be called as city metro lines, since they mainly run within city area or popular destination; As with line S1 and rest of metro lines, such as S3, S8 and S9, they are called airport line, which could directly run to Lukou International Airport and others are the extension of S1, running in the suburb.

Moreover, Nanjing is also 136th city that have a metro system, since the 1st metro in the world was introduced in London in 1863 [3]. On the other words, building up a metro system in Nanjing could take a step toward an international metropolis by enhancing the local transport system.

The Birth of Nanjing MetroEdit

After popularizing all-round reform and opening-up policy, China’s industrial technology is advancing to ever higher levels. With the improvement of the railway and metro system and in order to respond and make a contribution to national metro construction. Nanjing Municipal Committee proposed the plan for the construction of subway in 1984. After basic project evaluation, the national approval of Nanjing metro construction was officially established in 1994, and that means the Nanjing metro project officially starts and has undergone many adjustments or modifications to determine the construction ideas.

After two decades, the opening of Nanjing Metro Line 1 has enabled Nanjing to become the sixth metro city in China after Beijing, Tianjin, Shanghai, Guangzhou and Shenzhen [4]. During planning and extending metro network period, there is a planning report (called as ‘Nanjing Urban Rail Transit Network Planning’) always keeping updating and adjusting by China National Development and Reform Commission to indicate the following instructions of construction in the future [5].

Moreover, the type of Nanjing metro is urban rail transit, and let’s take the line 1 as an example: as for line 1, this line mainly runs in a north-south direction. It starts at Maigaoqiao station in the north and continues southwards towards China Pharmaceutical University station (CPU) station which is located at the southeastern side of Nanjing. Furthermore, it has two tracks both in opposite direction, with track gauge of 1435 mm and 60 kg/m heavy rail, and its metro system manly forms as tunnel, ground and viaduct form [6].

The Development of TechnologyEdit

Signal SystemEdit

  • The Birthing Phase: As for the technology applied to Nanjing metro system, in the early stage, the imported technologies (Trainguard MT, Vicos OC 501, Sicas ECC and Az S 350 U axle counting system) from Siemens Transportation System (TS) is supplied for line 1 and keeps supporting signal system for line 2 with local signal technology researched by Nanjing Research Institute of Electronic Technology (NRIET) [7].During Nanjing Metro line 1 and 2 construction, combining the technologies provided by international company and local research institute could permits optimum train sequencing commensurate with passenger levels and maximum safety, reliability and availability for metro operations by comparing with conventional automatic train control systems. Moreover, the planning and construction of line 2 carry through a sense of Belt and Road initiative, this encourage the project team to work with reliably international group, in order to absorb their essence and discard the dregs [8][9]; and the developed signal system applied on metro line 2 could ensure the metro lines will operate safely, punctually and in a user-friendly manner.
  • The Growth Phase: In the middle stage of Nanjing metro system, the government realized that introducing the advanced subway signal equipment from overseas has led to a rapid increase in signal systems. However, there are still existing several issues about introducing overseas techniques. The introduction of foreign technology is expensive, the maintenance cost of equipment renewal is very high, and the most important is the disorder of the system, which brings many difficulties to the expansion of the line network. Therefore, Nanjing city council decides to research domestic metro signal system in recent years and finally apply it to latest metro line S8.

Rolling StockEdit

  • The Birthing Phase: The rolling stock of Nanjing metro is mainly supplied by Chinese and French railway rolling stock manufacturers, which are called as Nanjing Puzhen Rolling Stock Works and Alstom, for example, six-car group trains are mainly used for metro line 1, 2 and 4 and few 4-cars or 3-cars group trains are operated only in metro line S8 and S9 respectively [10]. In addition, overhead contact line technique is applied for all Nanjing metro lines, allowing trains to slide on the overhead line system via pantograph, and hence it could receive electricity, and its gauge of steel wheel rail is 1.435m, however, this technique would induce few energy loss, transferring electric energy or kinetic energy to heat, to cause decreasing energy efficiency.
  • The Growth Phase: In order to deal with this issue mentioned as above and enhance the reliability of metro system, there is a new technique, which is called as permanent magnetic direct drive, being going to be applied on new metro as a new core technique, the aim of this technique is to connect electric motor with the carriage axle rigidly in order to minimize the energy loss (kinetic energy) and hence enhance the efficiency of electric motor and reduce the level of noise pollution, saving budget of project by reduce the cost of following maintain and repair. This technique is supposed to be used in new extension metro system in the future [11].

The Development of Early MarketEdit

Limitation of Other Transport ModesEdit

  • Limitation of Taxi: At the end of 20th century, driving private cars is not popular in Nanjing, since it could be too expensive for local citizen to buy one car. Hence, most people prefer to select public transport, such as taxi, bus or bike rather than buying a private car. As for selecting taxi, the price of taxi is reasonable, since it would not excess ¥20 if you travel inside the city area; However, the main issue is traffic jam for taking taxi, because of bad transport management in peak hour and narrow street in 1990.
  • Limitation of Bus and Others: As with bus, it would be the one of most popular transport mode before operating metro line 1. The reason why bus become popular is that traveling cost is very cheap, only taking ¥1 for whole trip or even¥1 additional fee for special bus with air condition. However, by considering other factors, bus is not reliable at that time, since its poor transport management system, low frequency and long-time bus delay would induce communities complain of any inconvenience. On the other hand, the end of 20th century also is the boom period of riding bike with around 523 million bike owners [12], since it not expensive to buy a bike comparing with buying a private car, and it is very convenience and flexible to travel anywhere, but it would not be safe because of poor transport management and policy related to riding bikes.

The Development of New MarketEdit

Firstly, by considering the weather conditions of Nanjing, the main advantages of subway is shown obviously as reliable and convenience; for example, when it rains or even snow, this would cause road water-logging and even ice pavement, showing taking taxi, bus or even bike would be very dangerous to travel, and at this time, metro network system would become the 1st choice of transport mode for every tourists. By comparing with other transport mode like cars or buses, metro could indirectly reduce the level of traffic congestion by encouraging people to choose metro, because of its large capacity (10-15 times capacity of standard bus) , very fast travel speed (usually taking 1-2 minutes to reach the next stop), cheap price (usually ¥2 for a short trip). Furthermore, building up Nanjing metro system could bring many advantages for society and environment. For instances, it could save the usage of land, because of the high cost of urban land in general metropolitan areas, the construction of railways on the ground can save floor space and allow ground land to be used for other purposes, and for Nanjing metro line 2, Nanjing government decides to replace viaduct, which always occurs traffic jam, as underground subway to save floor space; and it also can reduce traffic noise and interference, since metro system is an independent system underground and its timetable would not be affected by other transport mode. Besides, it could reduce the greenhouse effect as well, because it mainly uses electric energy rather than gasoline, hence there is almost no emission of pollution. Therefore, Nanjing metro system is reliable, convenience and environmental-friendly project to bring several benefits to Nanjing citizens.

The Life-Circle AnalyzeEdit

In the Birthing Phase (2005-2009)Edit

By taking example by Beijing and Shanghai metro, Nanjing metro system was ruled in 2005 when the 1st line was operating that the operator provides several types of tickets for customers to reach their demands. There are mainly three types of tickets people usually use, involving single trip tickets, Jinling card (or called as Nanjing Public Utility IC Card) [13]. As for single trip ticket, and the price of ticket is mainly based on the number of stops traveled at the beginning, and for instance, ¥2 ticket could travel 1-8 stations, ¥3 ticket could travel 9-12 stops and maximum price of tickets is ¥4 , meaning ¥4 could travel over 13 stations for 1 trips, and it is very cheaper comparing with other country metro system, although it was in the testing stage. Moreover, Jinling card is kind of deposit card, there would be discount (5% off for adults, half price for students and elders [14]) for ticket if people use Jinling card; and it is good that Jinling card also works on bus or even taxi, hence the initial aim of Jinling card is to provide multi-mode trips for local citizen in order to encourage them to choose public transport. Those ticket policies mentioned above were tested in 3 months and gained satisfied result and hence officially operated in September 2005.

In the birthing stage, several part of core techniques are mainly relying on the overseas company, especially like signal control system supplied by Siemens Transportation System (TS), and rolling stock supported by Nanjing Puzhen Rolling Stock Works and French company Alstom.

In the Growth Phase (2010-2016)Edit

There are several adjustments changing on the Nanjing metro ticket policy, after construction of metro line S1 and 4, Nanjing metro operator standardize the price of ticket by basing on mileage rather than number of stops in 2014, for example, ¥2 could travel 10km, once travel distance excess 10km, adding ¥1 for traveling extra 1-6 km, meaning ¥3 could travel 10 km-16 km [15]. In addition, Nanjing metro operator also tries to popularize several ways to encourage people to choose metro rather than private car in order to reduce traffic congestion. In middle of 2014, there are several discount cards, including month and season cards, putting on sale to put into trial use for 2 years. Those cards have fixed price and unlimited amount of mileage, since it looks like good for people who usually travel long distance. Unfortunately, during trail period, there are few people prefer to buy these cards, because of its low efficiency and wasting resources, hence these operations of month and season cards end in 2016.

Besides, during construction of metro line 2 in 2010, the domestic signal system was partially applied to Nanjing metro system, supporting by Nanjing Research Institute of Electronic Technology (NRIET). Chinese domestic core technology partially dominate the local market.

In the Mature Phase (2017-2021)Edit

In order to cooperate with the Nanjing city construction and according to latest ‘Nanjing Rail Transport Regulation’, Nanjing metro operator indicates that Nanjing metro would not allow any food or drinks in the carriage, metro staff would teach people to follow the metro new instruction as well and would ticket people who always knowingly violate the metro policy [16]. On the other hand, in 2015, Nanjing metro line S8 fully supported by Chinese domestic core techniques of signal system rather than importing overseas signal system, showing China has ability of independent research and technology in metro signal system area.

In the future, as with developing local domestic techniques, the extension of metro line 4 (extra 9.7 km) and S8 (extra 2.5 km) would keep constructing and according to the second vision of ‘Nanjing Urban Rail Transit Network Planning’, it indicates that there would be a new metro line, called as line 11 (27 km), building cross the south of Nanjing. These actions are going to plan in 2021 to enhance the connection between suburb and city area, reduce the level of traffic jam and increase the mobility in south area of Nanjing.

In the future, with rapidly increasing population, Nanjing metro operation could drive the migration of population from city area to rest suburbs and accelerate urban construction by transiting human resources within Nanjing city, hence more extension of original routes and additionally new route should be constructed in the future with development of city. At the same time, Nanjing metro operator also need to focus on public security by troubleshooting system and rails regularly and deploying enough police or security staff to make sure travelers’ safety. Moreover, there is a innovations that Nanjing metro system has to keep achieving a great job in connection between the main urban area and south or north suburbs and with other transportation modes by further studying the Nanjing metro system and basic management in order to promote the integrated development of urban and transportation.

Quantitative AnalysisEdit

Raw DataEdit

The data of the annual ridership for Nanjing Metro system from the end of 2015 to 2017, which is searched from Nanjing Metro official website, is shown as below:

Year Annual Ridership (Millions)
2005 18.00
2006 58.00
2007 80.18
2008 103.79
2009 113.53
2010 214.59
2011 343.71
2012 400.61
2013 452.16
2014 503.00
2015 717.01
2016 830.67
2017 977.11

Table 1: Raw Data of Annual Ridership for Nanjing Metro

According to Table 1, it is obvious that there is a rapidly increase of annual ridership in these 12 years.

Resultant CalculationEdit

Defining EquationsEdit

There is a three-parameters (involving K, b and t) equation is provided to operate the resultant calculation in order to help calculate the predicted passengers (unit in millions), the equation is shown as below:


  • S(t) is the estimated value of annual ridership in millions
  • t is current time in years
  • to is the inflection of time (achieving 1/2 K)
  • K is saturation status level
  • b is coefficient

And there is another formula using to calculate the regression:

Finding Proper Value of K and bEdit

Firstly, it is important to consider the largest value in the database, and set a series value of K. In this case, our largest value of data is 977.11 million in 2017, hence the first value of K set should be slightly larger than 977.11, so we set 980 million as the first value of K set. As for the rest of K set, it recommends to use trail testing to choose an best or appropriate choice finally; After testing, a reasonable K set has been selected, showing 1000, 1020, 1040, and so on.

Table 2: Possible K Set Database

In order to find out which K value is achieve to real situation, the following Table 3 illustrate the most real K value would have the largest value of SQR within the whole set; and hence the value of K is 1200 with corresponding values of b (0414811) and SQR (0.976939):

Table 3: Finding proper K and b Values
Table 4: Data Analysis of Regression Study

Calculating Estimated ValuesEdit

By using pervious three-parameters (involving K, b and t) formula, showing as below:

Table 5: Estimating ridership in current year

Drawing S-curve DiagramEdit

By using calculated data (raw and estimated data), it is able to draw a S-curve diagram shown as Figure 1; According to Figure 1, the estimated line fits the original line very well, but estimated line shows its tendency more smoothly. At the beginning, Nanjing Metro officially operates in 2005 with estimated value of 29 millions annual ridership, and the estimated value is much larger than its actual annual ridership (18 millions). It is obvious that the birthing phase of Nanjing Metro is between 2005 and 2010, since its ridership grows slowly with small slope, showing from Figure 1. However, it is boom period from 2011 to 2017 for Nanjing Metro system, since there is a significant rise of annual ridership for both lines, and estimates lines also fits the actual lines well, that means everything is on the plan, and this diagram also reflection real situation for Nanjing Metro system; for example, before 2010, Nanjing Metro system only has 2 metro lines, but after several years, the metro network is extended to 9 metro lines in service, and this enhances the connection between urban area and suburban areas and encourage more and more people to choose metro, and hence cause the rapidly increasing annual ridership in recent years.

Figure 1: S-curve of annual ridership for Nanjing Metro from 2005 to 2017


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