Topic 1 Public Transport System Design and Optimization Methods

• As mentioned, public transport service is performed by means of transport that operate on fixed lines. Public passenger transport by mode of operation and organization has the following basic features:
  • vehicles move between the two terminals A and B,
  • along a pre-determined route,
  • according to the established timetable,
  • stopping at all planned stops where passengers enter or exit the vehicle.

• Stations A and B represent the start and end terminal, and the relation between terminals A and B = the length of the line L. Each line has its own mark and name, which are placed on vehicles and stops.

• Each line of public transport is a subsystem in the system of public transport whose main goal is the transport of passengers between individual stops on the line.

• The public transport line is a part of a network of lines, and consists of:
  • route – the pre-determined direction in which the means of transport travel
  • stops – a place where means of transport stops for the entry and exit of passengers, and may have an information pillar, shelter and seats
  • terminal – final stops on public transport lines

• There are several types of lines within the network of public transport lines. The function of the lines and their number depends on the shape of the city, terrain configuration and the location and concetration of activities. Most lines have an irregular shape, but can be classified into several basic types:
  – radial,                                      – circular or annular,
  – diametral,                               – loop,
  – tangential,                              – main lines with branches and collection/assembly lines
  – circumferential,

• The public transport line consists of two elements: static and dynamic
• Static elements are as already mentioned: route, stops and terminals.
• Dynamic elements are divided into basic dynamic elements and derived dynamic elements. Dynamic elements are determined by the timetable which changes according to the transport requirements on the line.
• Basic dynamic elements are:
  • Number of vehicles on the line – all passenger transport is performed by vehicles that operate along the public transport line
  • Turn time – contains the time required for the vehicle to make one turn, which includes driving time, waiting time at stops for entry and exit of passengers, time spent at terminals.

• Derived dynamic elements are:
  • Vehicle interval – the time interval between two consecutive vehicles on the line. It is obtained as the ratio of turn time and number of vehicles on the line. It has minimum and maximum value. The minimum interval represents the minimum possible time spent between two means of transport on the line that may occur. The upper limit i.e., the maximum interval would mean that only one vehicle operates on the line, so it is equal to turn time.
  • Frequency – defined as the number of vehicles that pass through a specific point in a unit of time (usually an hour). It is the ratio of the number of vehicles and turn time.

• The classification of lines in the city area is done according to different criteria:
  1. Depending on the character of the served territory, the lines are divided into:
     – urban lines
     – suburban lines
  2. Depending on the importance and impact on the shape of the network and the mode of operation:
     – main lines
     – collection/assembly lines
  3. According to the mode of the operation:
     – permanent lines
     – occasional or seasonal lines
  4. According to the character of the route:
     – independent lines
     – interconnected lines
  5. Depending on the way the line is provided in relation to the territory of the city (city borders), especially in relation to city centre:
     -radial – connecting the city centre with the peripheral parts of the city
     -diametral – connecting two peripheral parts of the city and passing through the city centre
     -tangential – connecting two peripheral parts of the city, but don’t pass through the city centre
     -circular – with their route they close the circular direction of traffic
     -semi-circular – with their route they represent the part of a circular line
     -peripheral – connecting two points on the periphery of the city

• Planning the network of public urban transport lines can be classified into three categories of objectives:
  • achieving maximum transport – can be expressed by the number of passenger/travel or passengers/kilometre. This includes offering high speeds and average travel lengths that do not vary
  • achieving maximum operational efficiency – this goal can be expressend as the minimum total cost of the system for a given level of performance
  • creating positive effects – they include different effects, from short range ones, such as the reduction of congestion on roads, to goal of higher reach, such as achieving high population mobility, desirable tracing of public transport network, sustainability and high quality of life.

• The basic criteria for assessing the network of public transport lines is:
  • the route of the line should be harmonized with the passenger’s travel wish lines, which is determined by surveying, interviewing, recording, counting, etc.
  • walking to the stop in the city centre must be up to five minutes, and outside the centre up to ten minutes
  • the network of lines should be traced so that most passengers reach the destination by direct line or with a maximum of one transfer to other lines
  • switching to other lines and means of transport must be safe, easy and comfortable
  • wherever possible, the greatest possible independence of public urban transport lines from other participants should be ensured

• The following factors need to be considered when designing a public urban transport system:
  
  • land use
    
  • topography and environment
    
  • geographical constraints
    
  • existing transport network

• It is important that transport technologists with experience in the operation of public transport systems actively participate in the design of lines and network lines

Source: Šoštarić, M., Jakovljević, M., Buhin, D., Ševrović, M., Lale, O., Beganović, D.: Study of Public Transport in the area of the City of Jastrebarsko, University of Zagreb Faculty of Transport and Traffic Sciences, Zagreb, 2017

• Public transport timetable modelling is the process of calculating the frequency of service, the number of required vehicles, travel time, turnaround time and other elements. Timetables can be graphic and numerical and can be made for operators and transport technologists (known as paddles)

• Timetable modelling can be divided into five phases:

1. 1. Phase I: data preparation and factor determination
   2. Phase II: interval and frequency calculation
   3. Phase III: determine the size of the vehicle fleet
   4. Phase IV: calculation of cycle and retention time at the terminal
   5. Phase V: cycle speed calculation

• The result of the timetable planning phases are numerical and graphical representations of the public transport line. Graphical representations such as diagrams can be very effective in traffic and timetable planning and public transport system analysis. They offer a better overview of the interval regularity, as well as meeting locations and details of operations on a line or the impact of timetable changes

Source: Štefančić, G.: Urban Transport Technology II, University of Zagreb Faculty of Transport and Traffic Sciences, Zagreb, 2010.

• There are several types of graphical timetables, from conventional path-time diagrams to timetable displays on complex multi-line networks. The basic graphical timetable is a path-time diagram with a line (distance-path) on y-axis and time on x-asis. As showed on diagram, that line is divided into sections with flat speed. Entering each ride of the transport unit, marked with a number, shows all elements of the timetable: travel time, speed, etc. for each transport unit on each section and each terminal. X-asis (time) shows the intervals as the distance between two consecutive departures of the same ride from the terminal.
• The whole diagram shows: arrivals and departures of transport units at each stop along the line, retention times at the terminal, locations and times where the transport units meet.
• To simplify input and improve readability, it is common to use a real-time/operational-time diagram and enter the operating time between two terminal on the y-axis, instead of the distances.

Working hours and ride division (run-cuts)

a)Typical diagram of working hours

b)Allocation of rides for working hours under a)

• An important factor in timetable modeling is both the schedule and the number of staff required to maintain quality service. The allocation of staff to a particular timetable should be such that the total cost is minimal
• As the amount of service offered varies on days of the week and hours during the day, the driving staff works irregular hours. Large number of passengers during rush hours require different timetables during the day
• In order to meet the unequal demand for drivers during the daytime hours of the week and on weekends, working hours are planned in different forms:
  • Straight ride – basic shift with continuous driving of eight hours
  • Split ride – during the rush hour more drivers are needed and must be deployed to work during two rush hours with unproductive paid or unpaid hours between
• The basic procedure for allocating rides consists of the following steps:
  • Develop as many straight rides as possible
  • Form split rides within a time range
  • Divide straight rides into two or three segments and combine segments with the extras left from the previous step to form additional split rides
  • Analyze the effectiveness of the resulting solution if it is not satisfactory

• According to economic rules, prices must be set at a level at which the demand curve intersects the marginal cost curve. This means that the cost of a marginal unit is equal to what the customer is willing to pay. This gives the most efficient use of resources and increases social well-being
• In the normal situation, the demand curve intersects the marginal cost curve at the output, where the average cost increases so that the marginal cost is higher than the average
• By assuming a flat price (which is common in most markets), the price is the same as the average income. If the price is equal to the marginal cost, then the average revenue will exceed the average cost, the total revenue will exceed the total cost, and the company will make profit

Pricing in the normal market

Source: Štefančić, G.: Urban Transport Technology II, University of Zagreb Faculty of Transport and Traffic Sciences, Zagreb, 2010

MC – marginal cost

AC – average cost

D – demand curve

Price and quantity are determined by the intersection of the demand curve (D) and the marginal cost curve (MC) at point G. For quantity OE, the average cost curve (AC) is below the marginal cost curve. The average revenue is EG and the average cost is EF, so there is a profit from FG on each unit sold.

• Fares are the basic work element in the public transport system. They affect on the attraction of passengers and the financial condition of public transport company. Fares planning requires consideration of interrelated aspects to select the most efficient type of fare

• In order to determine the fares for the public transport system, it is necessary to define the objectives:
  • attracting the maximum number of passengers
  • achieving the maximum revenue for the public transport company
  • increasing the maximum mobility of users (labour, students, seniors, etc.)
  • improving access between certain areas
  • modernization of public transport

• Fares structures are classified according to the price and distance travelled. Using this criterion, there are two types of fares: flat fare and graded fare
• Flat fare is a fixed amount that depends on the length of the trip. It is the simplest possible fare because it is easy for passengers to understand and use
• Graded fare serves to avoid injustice to passengers traveling short distances and is divided into zonal fare (proportional to the length of passenger travel, achieved by dividing the city or urban area into zones) and sections fare (achieved by dividing public transport lines into sections and increasing according to the number of passed sections)