s.glumac/^ j.petrovic,^ s.zezelj^ - wit press€¦ · • passenger number and turnover entrance...

The characteristics of buses for public urban

transport and the environment

S.Glumac/ J.Petrovic, S.Zezelj^ Bus factory - IKARBUS, Autoput 24, Zemun, YugoslaviaUniversity ofBeograd, Faculty of transport and traffic engineering,Vojvode Stepe 305,Beograd, YugoslaviaEMail: pjelka@Eunet. Yu

Abstract

This paper presents the methodology of research done on the influence offunctional characteristics of buses on the environment. The results concerningthe research of the influence of bus characteristics on the efficiency of public citypassenger transport are presented. Also, the paper gives results of research of theinfluence of vibrations on the working condition of the driver and passengercomfort. The research was done under real conditions of bus exploitation inBeograd.

1 Sustainable development and public transport

The concept of sustainable development assumes the use of natural resourcesand manufactured goods in such a way as to "satisfy the needs of the presentgeneration without endangering the needs of future generations". Sustainabledevelopment would also assume the permanent betterment for all. This conceptis based on several key principles. The first and most important is the unificationof economics and ecology in such a way as to be the principle decision-makingcriteria on all levels. This is the least controversial principle because itpresupposes the integration of ecological criteria in economic decision-making.

It goes without saying that the ideas of environmental protection anddevelopment are not incompatible especially if development is seen as a newqualitative form of social and economic development which does not assumelarger material and energy consumption in the developed countries. Questionsconcerning the definition of the concept of "environmental capacity" and the

Transactions on the Built Environment vol 41, © 1999 WIT Press, www.witpress.com, ISSN 1743-3509

172 Urban Transport and the Environment for the 21st Century

"consumption of the environment" on a global and local level, reaching standardsand indicators concerning the environment and the reaching of a social andpolitical consensus on all levels, are but few to which an answer must be foundin order for the concept of sustainability to become more concrete in terms of anew socio-developmental paradigm (Cooper*).

The strategy of promoting sustainable mobility is based on the Green Paperpublished by the European Commission in 1992. The basic elements of thestrategy are:

The planning of land use; the reduction of the need for mobility and researchinto alternatives to road transport;The planning of infrastructure taking into account positive and negativeeffects on the environment;Taking measures to upgrade the competitive position of those modes oftransport which contribute to the preservation of the environment;Technical improvement of vehicles and fuels;Taking measures which would enable a change in behavior regardingvehicle use in all respects (COM ).Public transport in this context has a special significance. It is obvious that

certain types of transport have significant negative external effects: noise, airpollution, space use etc. Public transport is becoming more important as a meansto lower the growing external costs, especially in urban areas.

Developed countries in absolute terms are the largest polluters, but withvarious economic and political measures and strict standards are reducing theshare of transport in pollution. Other countries are relatively smaller polluters buthave a greater need for speedy economic development and their ecologicalconsciousness and total potential do not enable them to invest in cleantechnologies and high quality traffic systems. This means that these countriescould become large polluters.

The development of urban transport in the countries in transition depends ontheir economic and financial capabilities as well as the decisions made bynational and local governments in this regard. This is especially the case withtraffic infrastructure, the building of the road system and the renewal of thevehicle pool. The renewal of the bus vehicle pool is of utmost importance inrespect to the preservation of the environment.

In order to stimulate a growing number of passengers to use public citytransport (PCT) it is necessary to harmonize the level of service with consumerdemands. In affluent societies passengers have various means of transportation attheir disposal: car, taxi, bus, tram, subway and all of these with a variety of levelof service. In these circumstances important characteristics regarding quality andcomfort of passengers are punctuality, speed, reliability, etc.

For most passengers in the developing countries and the countries intransition the use of public city transport is not their choice but practically theonly possibility to satisfy their transport needs. For this reason the mostimportant demand is to reach the destination at the neglect of all other qualitycomponents. Unfortunately, in a great number of cities in the world the


Urban Transport and the Environment for the 21st Century 173

conditions of public urban transport are such as to make the maximum number ofpassengers per bus an important parameter.

Beograd is a example of a city in which there is a great discrepancy betweenthe supply of transport capacities and the demand for transport services. Thismakes the maximum use of available bus capacity especially important.Research on the efficiency of buses in extreme conditions of exploitation enablesbus producers to adapt bus construction to real work loads (Petrovic ).

Research on the influence of bus characteristics on the efficiency of publiccity transport the results of which are presented in this paper was done inBeograd. The goal was to define the optimal characteristics of buses that haveextremely difficult conditions of exploitation. The city transport company as theuser and the IKARJBUS bus factory were involved in the realization of thisproject.

2 Research Methodology

Research of the influence of bus characteristics on various aspects of theiruse includes two types of activities:

• Research of the influence of bus characteristics on the efficiency oftransport,

• Research of the influence of bus characteristics on the comfort andsafety of passengers

The research methodology on the influence of vehicle characteristics on theefficiency of transport was based on:

• Choice of representative public transport line• Identification of the characteristics of transport demands and

flows of passengers on line (passenger entrance, passenger exit,passenger flow)

• Characteristics of passenger flows• Basic elements of the structure of line functioning (static line

elements, dynamic line elements, line performance)• Defining parameters of vehicle quality (speed, efficiency and

transport capability, passenger safety and comfort, reliability,economic efficiency)

The results of research should enable the optimization of passenger space inthe early phase of bus design. The specific conditions of exploitation should betaken into account at this stage. The goal is reached if the following effects inbus exploitation are achieved:

• a better distribution of standing and sitting space,• a better passenger flow through the bus,• a better distribution of load,• faster entrance and exit of passengers,• shorter periods at stops,• lower costs of bus exploitation, etc.



The methodology of research regarding the comfort and safety of passengerswas based on having most of the measurements done during the regularexploitation of buses on their public transportation lines. The driver andpassengers are subject to various loads among which the vibrational, acousticand microclimate ones are of most importance. The negative loads and thefatigue of the passengers and driver due to them, can be reduced and eveneliminated in the phase of bus design, as well as by the proper upkeep of the busduring its long-term exploitation. International standards have been defined andprecise criteria for the time exposure to detrimental effects of vibrations andnoise, as well as criteria for the determination of the state of the thermalenvironment, have been set.

3 Results of Research

3.1 The influence of bus characteristics on the efficiency of transport

This paper presents the results of research of the influence of floor height andthe distribution of doors on the efficiency of bus exploitation. The height of thebus floor, the number, dimensions and distribution of doors are buscharacteristics which influence the concept of bus design and production. Forthis reason information on the influence of these characteristics on the efficiencyof bus exploitation is of importance both to the producer and user of buses. Bythe use of the same methodology it is possible to determine the influence otherdesigns such as the number and distribution of seats, the dimensions anddistribution of handles etc., on the efficiency of bus exploitation.

The research was done on three different models of buses of standarddimensions that are produced by IKARBUS. The basic vehicle used in theresearch was the basic IK 103 bus model for urban transport with three doors andfloor height of 910mm. The IK 103/4V bus has the same floor height, while theIK 106 model is a bus with three doors and a floor height of 315 mm. All of themodels have the same nominal capacity and are of the same dimensions.Two independent public transportation lines in Beograd were chosen. The choiceof the lines was such as to best approximate the conditions of bus exploitation inBeograd. The following were researched (Glumac*):

• the speed of entrance and exit of passengers• periods of time spent in stops• passenger number and turnover

Entrance and exit of passengers. The distribution of entrances and exits ofpassengers by respective doors is given in the following tables (F- front door, M- middle door, R - rear door). The middle door of the IK 103/4V bus was enteredby over 52%, and was used for exit by approximately 55% of the passengers.This makes this model of the bus different from the other two models in whichthe middle door was used by 42 - 44% of the pb engers (entrance) and 47-53%(exit). This indicator shows the distribution of passengers and bus load.



Table 1 : the distribution of entrances and exits by door IK-103/4 V

Passenger entrance

F

419

18.2%

MI

591

25.7%

M?

605

26.3%

J20P%

R

682

29.6%

Sum

2297

10094

Passenger exit

F

390

16.9%

MI

539

23.494

M;

725

31.594

JJ.OJ%

R

643

27.9%

Sum

2297

100%

Table 2 : the distribution of entrances and exits by door IK-103

Passenger entrance

F

549

26.7%

M

862

41.996

R

645

31.394

Sum

2056

10096

Passenger exit

F

507

24.6%

M

968

47.1%

R

581

28.2%

Sum

2056

100%

Table 3 : the distribution of entrances and exits by door IK-106

Passenger entrance

F

228

21.494

M

468

44.0%

R

366

34.4%

Sum

1063

10096

Passenger exit

F

201

18.9%

M

561

52.7%

R

300

28.2%

Sum

1063

100%

Periods of time spent in stops. Research concerning the type spent in stopsshowed that it does not depend on the number of doors. For all three types ofvehicles the average time spent in stops was between 15 to 18.5 seconds.

Table 4 : Comparative characteristics of the distribution of time spent in stops.

Time spent in stops(seconds)

No. cases(IK-103/4v)

No. cases (IK- 103)

No. cases (IK- 106)

0-10

69

50

38

10-20

79

76

40

20-30

22

24

16

30-40

12

20

2

40-50

10

9

3

50-60

5

<->j

1

>60

5

2

1

Sum

202

184

101



Bus type

IK-103/4v

IK- 103

IK- 106

Average time spentin stops (seconds)

17.45

18.37

14.95

Standard deviation

14.04

12.82

11.14

Coefficient ofvariation

0.805

0.698

0.745

Speed of passenger turnover. The table gives the number of passengers bysemi-turnover and their distribution by door as well as the total time spent onstops. On the basis of this data the time used for entrance and exit of passengerswas calculated.

Table 6 : Comparative results of research relating of passenger entrance

Bus type

IK-103/4v

IK- 103

IK- 106

TVb. ofpassengersby semi-turnover

229.7

205.6

177.17

Time spentin stops inrelation to

semi-turnover(seconds))

406.8

373.7

324.5

Averagetime ofentranceand exit ofpassengers^ecoMdVpassenger)

1.77

1.82

1.83

Minimaltime ofentranceand exit ofpassengers(seconds/passenger)

0.65

0.67

0.91

Maximaltime ofg/?//"a/7Cand exit ofpas'.sgMgerj(seconds/pajjgfige/))

2.49

3.46

2.76

Exploitation load. The minimal capacity of buses for mass transport ofpassengers in the city is defined by the number of seats and standing room, whileevery bus manufacturer defines these according to his own criteria.

The real load of the bus changes along the public line and is greater or lowerthan the nominal capacity. The real load depends not only on the parameters ofthe passenger space but also on the actual density of standing passengers. Theactual density standing passengers depends on the speed of passenger turnover,transport demand and the use of standing space.

Passenger turnover and their distribution within the vehicle depend onparameters such as: floor height, number of steps and their dimensions, thenumber, position and dimensions of the platform for the entrance of passengers,the width of space between the seats, the distribution of handles etc.

The vehicle load is heavily influenced by the correspondence between linecapacity and transport demand (the number of passengers), the periods in stopsand the reliability of keeping to the bus schedule. The results of research of thereal load of the buses used as representative is given in table 7.



Table. 7 Percentage of road traveled under certain levels of loadLoad /%/

ModelIK- 106 max 1 10 passengIK- 103 max 1 10 passengIK- 1 03/4 V max 1 10 passeng

up to30%36.2%32.8%33.6%

30-80 %

57.1%52.9%46.2%

80-100%

6.7%12.19414.6%

Over100940%2.2%5.6%

3.2 The influence of bus characteristics on passenger comfort

The results of the research are of special importance for bus design keepingin mind that the satisfaction of user and consumer demands primarily meanscomplying with the demand for safety and comfort. All the results shown in thispaper were obtained in conditions of real bus exploitation.

Here we present the results of research of the influence of oscillation effectson the driver and passengers.

3.2.1 Oscillation effects on driver and passengersOscillations to which driver and passengers are exposed in buses are ranked

amongst the most unpleasant detrimental effects. Low-frequency appearanceswith frequency of up to 80 Hz make the portion of the spectrum to which humanbody is most vulnerable. Peak values of acceleration, their direction, frequencyand time of exposure to oscillations are of the most essential influence on thehuman body.

Standard ISO 2631 defines a method for evaluation of disturbances provokedby oscillations to which the human body has been exposed during the drive. Thestandard provides tables and diagrams showing limits of permitted exposure tooscillations for three different criteria:

- permitted limit from the aspect of comfort,- permitted limit from the aspect of working ability and- permitted limit from the aspect of protection of human health.

The measurements have been carried out by means of the measuringinstrument B&K 2512. It has been made according to standard specificationwhich takes into account time of exposure to oscillations, as shown in Fig. 1.Measurement takes into account duration of exposure to oscillations subject tointensity. By using tables and diagrams from the standard, one evaluates workingtime of a driver, subject to duration of exposure to particular accelerationamplitudes, related to given limitation curves. Comfort of passengers isevaluated in the same way.

Measurements necessary for evaluation of vibrations effects to which man isexposed in vehicles have been carried out by measuring equipment of B&KCompany:

- Human response vibrations meter, type 2512- Triaxial Accelerometer, type 4322.

This system measures and analyses vibrations to which man is exposed invehicles and provides:



equivalent exposure to vibrations, in percentage of permitted dose for agiven period of time Eexp;equivalent continuous vibrations level which presents the mean vibrationslevel distributed along the entire measuring period. Vibrations levelmeasured this way has the same power as the variable signal measuredduring measuring time, as per the following formula:

(1)

where Leq is expressed in dB. Acceleration reference value is a=10~^, whereasa(t) presents the measured acceleration (in ms~"). The apparatus 2512 gathers,squares and records its measurements in digital memory. Value Leq is beingcontinually re-calculated on the basis of distribution of values accumulated in thememory and is shown on display for the entire period of measuring;

- peak value of acceleration level in duration of measuring Lewqmax (dB);- duration of measuring time.

The measurements have been effected in three mutually orthogonal axes, onthe driver's seat, on a passenger seat in the middle and on a passenger seat in therear end of the bus (above the engine); in urban driving conditions, in driving atconstant maximum permitted speed on a good asphalt road, and in driving alonga very poor asphalt road at constant, greatest possible speed (Mladenovic ). Theresults of measuring are shown in tables 8 and 9.

For calculating ELeq resulting acceleration is calculated as per ISO 2631:

(2)

Measurements on Passenger SeatsTable 8 : Equivalent acceleration level on passenger seat in the middle of bus inurban driveAxisXYZ

Leq (dB)106.5104117114.2

Peak (dB)119125128

Time (min)555

Measurements on Driver's SeatTable 9: Equivalent acceleration level on driver's seat in drive on extremely badroad surface V = 40 km/hAxisXYZ

Leq (dB)117.5111.5121128.8

Peak (dB)122121134

Time (min)555



Evaluation of vibrations effect on the driver is made according to a reductionof working abilities during working time. Pursuant to service conditions in whichthe measurement has been carried out, evaluation of the measured values, as perFig. 1, one may conclude as follows:- driver in urban drive, as per criterion of reduced working abilitycan drive vehicle continually but not longer than 5 hours;

- in out-of-town drive, on a very bad asphalt road, at constant speed of 40 km/hthe criterion of reduced working ability is fulfilled in the first minute.According to criterion of endangered health the time of continual vehicledriving in these conditions could last 40 minutes only. This result is theconsequence of the very bad condition of asphalt surface and inadequaterunning speed and it does not comply with realistic conditions of PCT busservice.

- On passenger's seat in the middle of bus, according to criterion of reducedcomfort, the time of "comfortable ride" is:

- in urban drive 3 hours and 30 minutes,- on good asphalt road 4 hours,

- On passenger's seat above the engine, at the rear of bus, according tocriterion of reduced comfort the time of "comfortable ride" is 30minutes,For a passenger standing on the front platform, next to driver'scompartment, the criterion of reduced comfort cannot be fulfilled, whereasthe criterion of reduced working ability provides the time of 45 minutes.

4030 -201510

•S 3,2 •1 251,5in 1,0-1 0.8 -

0.2

» 0,1"- 0,08

0,05

Hand Arm-Uninterrupted(Reference Frequency 160 Hz

Whole-Body Exposure LimitWhole-Body Fatigue Dec. Prof.Whole-Body Reduced Comfort

Ref. Freq. (a,) 4 to 8 Hz" (a, and aj 2,8 Hz

Motion Sickness Severe DiscomfortReference Frequency 0,1 to 0,3 Hz

Motion Sickness Reduced ComfortReference Frequency 0,36 Hz

1,5-2 3—4-5-6-8-10—15-20 2530 40 50 min-Exposure Time0,1h 0,5h 1h I,5h2h 3 4 5 6 8 1012 16 2024

Fig 1 .Frequency-weighted amplitude versus time weighting functions built intothe B&K 2512. The form of the permissible limit lines shown are as prescribedin the relevant standards and recommendations and are normalised to thereference frequencies indicated



4 Conclusions

The efficiency of public city transport can be improved by using buses whosecharacteristics are adapted to working conditions. By using the bus with doublemiddle doors the efficiency of exit and entrance is improved by 7-8% whichmeans that the number of passengers can be increased by the same percentage.All of this goes at their expense of passenger comfort. However, incircumstances in which buses are lacking passengers are willing to give upcomfort in order to get to their destination. Under these conditions the use ofbuses with lower floor height does not bring up efficiency. The comfort that isassociated with low floor buses in terms of easier exit and entrance for thepassengers, as well as easier access for the handicapped, can not really manifestitself.

The results of the research enable:• the producers to adjust their production and various project

solutions to the demands of the users.• the provider of public transport to chose in a quick and efficient

way the optimal type of bus in accord with the projected priorities.

References

1. Cooper,C; Economic Evaluation and the Environment, Hodder andStoughton, London, pp. 25, 1981.

2. COM, Green Paper on the Impact of Transport on the Environment: aCommunity Strategy for Sustainable Mobility, pp. 46, 1992.

3. Petrovic,J., & Zezelj,S., Economic development in the countries intransition and its effects on urban transport, Technika, Vilnius, pp. 125,1998.

4. Glumac,S., Optimization of Bus Technical and EconomicalCharacteristics at the Designing State, Ph.D thesis, School of MechanicalEngineering, Beograd, pp. 90-97, 1997.

5. Mladenovic,D., Dedovic,V., & Zezelj,S., City buses comfort parameters"in service" testing, Urban Transportation, Beograd, no. 1/2, pp. 39-41,1997.


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