high-class transit in aalborg high performance bus - brt · 2 executive summary 8 3 introduction 9...

MAY 2014

HIGH-CLASS TRANSIT IN AALBORG

HIGH PERFORMANCE BUS

BENCHMARK OF BUS ROLLING STOCK FOR BRT SYSTEM TECHNICAL NOTE

MAY 2014 HIGH CLASS TRANSIT IN AALBORG


BENCHMARK OF BUS ROLLING STOCK FOR BRT SYSTEM TECHNICAL NOTE

ADDRESS COWI A/S

Visionsvej 53

9000 Aalborg

Denmark

TEL +45 56 40 00 00

FAX +45 56 40 99 99

WWW cowi.com

PROJECT NO. A047901

DOCUMENT NO. 008-01c

VERSION 3.0

DATE OF ISSUE 27-05-2014

PREPARED A. Pequignot

CHECKED T. Delettre

APPROVED JM. Mirailles

AALBORG HIGH CLASS TRANSIT SYSTEM


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CONTENTS

1 Resumé 7

2 Executive summary 8

3 Introduction 9

4 Technical requirements for Aalborg BRT 10

5 Operation & Vehicle capacity 11

5.1 Forecasted traffic for Aalborg’s project 11

5.2 Vehicles’ length 12

5.3 Operational feedback 15

6 Optical guidance 16

6.1 System characteristics 16

6.2 Operational feedback: Rouen (France) 18

6.3 Cost of an optical guidance system 19

6.4 Limits of optical guidance systems 21

6.5 Alternate option: pallets to fill vehicle – platform gap 21

6.6 Comparative analysis for bus accessibility 23

7 Hybrid motorization 26

7.1 Different types of hybrid engines 26

7.2 Scope 28

7.3 Vehicles on the market and operational feedback 29

7.4 Investment cost 30

7.5 Operational cost 31

8 Trolley bus system 32



7

1 Resumé

Dette arbejdsnotat omhandler materiel til højklassede busløsninger. Det indeholder

et benchmark og en screening af materiel, som kan bidrage til etablering af en

højklasset buskorridor i Aalborg.

Notatet behandler tre hovedemner:

› Bussernes kapacitet

› Systemer til optisk ledet styring og øget tilgængelighed

› Motorteknologi.

I forhold til bussernes kapacitet sammenlignes 18m ledbusser og 24 m

dobbeltledbusser, hvor 18 m bussen kan rumme op til 120 passagerer og 24 m

bussen op til 150 passagerer.

I forhold til indkøb af materiellet giver dobbeltledbusser udfordringer i forhold til

en højere omkostning og et begrænset udbud af mulige leverandører (i øjeblikket

kun 3 producenter). Derudover stiller driften af dobbeltledbusser særlige krav i

forhold til kurveradier og længden på stoppesteder. Der er eksempler på, at det

ekstra led indebærer problemer med passagerkomforten i bussen.

Den optiske ledning af busser kan forbedre busdriften. Det øger komforten for

chaufføren og forbedrer adgangen til bussen for passagererne via en bedre styret

tilkørsel til perronerne. I Rouen har den optiske ledning bidraget til driftsmæssige

forbedringer. Det er imidlertid også en teknologi med visse udfordringer (få

leverandører, funktion under klimaforhold med sne, økonomi mv.), hvilket

nødvendiggør særlig opmærksomhed. Særlig de driftsmæssige udfordringer i

vintermånederne kan hindre brug af løsningen i Aalborg.

Forskellige motorteknologier er belyst. Forskellige hybridløsninger – seriel og

parallelhybrider – er beskrevet. Disse løsninger er designet til brug i bymæssig

bebyggelse og karakteriseres ved et mindre brændstofforbrug og mindre

støjemissioner. Flertallet af busleverandører tilbyder hybrid løsninger og

erfaringerne hermed er generelt positive, selvom omkostningerne er højere og

busserne kræver dyre vedligeholdelsesarbejder hver 5-8 år i forbindelse med

udskiftning af akkumulatorer.

8 AALBORG HIGH CLASS TRANSIT SYSTEM HIGH PERFORMANCE BUS

2 Executive summary

This technical note deals with high performance bus services. It offers a benchmark

and a market screening of the main solution existing to better the performance of

bus services.

Three main topics are addressed:

- The buses capacity ;

- The technologies of optical guidance and pallet systems ;

- The motorization and power supply most advanced technologies.

Regarding bus capacity, we compared solutions with articulated buses (18m) and

bi-articulated buses (24m). Compared to the acquisition of articulated buses, the

purchase of bi-articulated buses presents some brakes such as their much higher

costs and the reduced offer (only 3 manufacturers). Moreover, the operation of

such bi-articulated buses is much more complex since it requires particular

adjustments of the infrastructure (radius of gyration on roads, length of the stations,

etc.). In compensation, apart from the obvious one of offering more capacity, the

advantages of using a bi-articulated bus are not obvious since in some cases those

bi-articulated buses were criticized for their lack of comfort for passengers.

Concerning optical guidance technology, it seems a seducing technology to

improve the performances on a bus network. It offers optimal comfort to drivers

and an easier access to buses. On some bus networks, the optical guidance enabled

to improve the performances in operation (Rouen). Nevertheless, it is a significant

choice which has also its drawbacks (very few manufacturers on the market,

climatic issues, extra design issues, extra cost issues, etc.) and has to be considered

with anticipation and great care. In the case of Aalborg, the main brake could lay in

the extreme climatic conditions.

About the motorization, the hybrid motorization market is screened. The different

types of hybrid engines (series hybrid traction, parallel hybrid traction) are

described. Those hybrid engines are generally designed for repeated sequences of

speeding and braking, hence in urban setting. They can also offer fuel savings and

reduce noise. Most of the manufacturers propose buses with hybrid engines, and

today the feed-back from the networks using hybrid engines buses is quite positive.

Of course the purchase cost of those buses is higher; as well as such buses require

some specific heavy maintenance every 5 to 8 years.

To conclude, the trolley bus system – which can be complementary with the hybrid

motorization system - is also described.



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3 Introduction

The articulated buses used for high performance bus projects are fully accessible

for all users. Doors are large and vehicle’s floor is at platform height. Getting on

the bus doesn’t require to climb any step, which allows an easy entry for

passengers with reduced mobility capacities (people using a walking sticks,

pushchairs, carrying luggage, etc.) or passengers with disabilities (using a

wheelchair, blind people, etc.).

The inside design of the vehicle facilitates passenger flows. Inboard comfort is

inscreased, thanks to the existence of sliding doors that open on the outside,

combined with an efficient cooling ventilation system, and adapted equipment

providing passenger information with live updates, as well as CCTV cameras.

Vehicles’ outside design has been conceived so as to allow passengers to identify

the specificity of the line and its high level of service. Buses meanwhile also bear

the colours, logos, and graphic identity associated with the city’s transport network.

Modern articulated buses also respect all current European norms in terms of

environmental protection.


4 Technical requirements for Aalborg BRT

High performance bus services are conceived to provide passengers with a level of

service close to the one provided by tram systems. Rolling stock is an essential

component for a given public transit system (along with stations and equipment), it

must thus comply with a number of technical and quality requirements.

A number of questions can be raised for Aalborg’s project with regards to the

choice of rolling stock:

- Rolling stock capacity : articulated buses or bi-articulated “mega” buses,

- Opportunity of optical guidance system (to facilitate station approach)

- Type of motorization and power supply: diesel, hybrid, trolley etc.

The decision process will have to take into account these three dimensions

simultaneously. As a matter of fact, if choices are made separately regarding each

question, the scope of available bus rolling stock on the market might be very

narrow and prevent Aalborg LRT from fully benefiting of the trading competition

between rolling stock manufacturers.



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5 Operation & Vehicle capacity

This section discusses about the type and number of vehicles (18 or 24m long)

needed to absorb the entire demand for transport on the project’s corridor while

guaranteeing optimal time intervals between buses during peak hours. In order to

do so, estimates have been made taking into account a maximal capacity of 4

persons per square meter, thus respecting comfort specifications and a time interval

of 4 minutes between each bus (per direction) at peak hours.

It has to be noted that bus manufacturers overestimate rolling stock capacity. It is

important to reason taking into account practical, and not theoretical, capacities.

Operational experience has indeed shown that it is practically impossible to fully

use the entire capacity of a given rolling stock, as passengers do not spread

themselves evenly within the vehicle.

5.1 Forecasted traffic for Aalborg’s project

Ridership forecast in the project’s corridor were estimated taking into account

current demand for public transit. It was calculated that the most loaded section of

the line (between JF Kennedys Pl and Karolinelund) would see a ridership of 1 300

passengers per hour per direction. This number represents only the load on the new

line: additional bus lines shall be running on the same corridor.


5.2 Vehicles’ length

In this section two type of bus rolling stock have been examined according to their

length:

- 18 meters (articulated bus)

- 24 meters (bi-articulated bus or “mega bus”)

In each case, standard bus width is 2.5 to 2.55m, without wing mirrors (additional

0.25m on each side of the vehicle).

5.2.1 Technical characteristics of articulated buses

Most articulated buses have a length comprised between 17.8 to 18m. The range of

available vehicles is not as wide as it is for standard buses, however, as they are

generally derived from them, they have benefited from similar technical evolutions

in terms of accessibility, comfort, and energy supply.

As of today, a dozen of articulated buses are available on the market (they are all

equipped with low floors).

The capacity of such buses is comprised between 100 to 120 passengers (including

approximately 40 seating passengers), for a cost of approximately 350 000 €.

For such capacity, the required headway to cope with demand of 1 300 passengers

per hour per direction would be from 4’40’’ to 5’30’’.

Citaro GNV bus (Bordeaux,

France) Inside view of CITARO bus

Figure 1 : Citaro bus (Bordeaux, France)



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5.2.2 Technical characteristics of bi-articulated buses

The capacity of such buses is comprised between 130 to 150 passengers, including

approximately 55 seating passengers.

For such capacity, the required headway to cope with demand of 1 300 passengers

per hour per direction would be from 6’00’’ to 6’55”.

If the cost of a mega bus is estimated around 600 000 to 700 000€, it can however

go over 1 000 000€ for a high performance bus system.

Generally speaking, the choice of a 24m long bus requires raising the question of

available rolling stock on the market for bus manufacturing.

Currently, only three manufacturers officially offer 24m long buses. However some

manufacturers are considering the development of very high capacity buses, among

which Solaris, which might soon be able to deliver mega buses. These 3

manufacturers are APTS, Hess, and Van Hool, which have all replied to the

invitation to tender for Metz’s high performance bus project in France.

It has to be noted that among these 3 manufacturers, only Van Hool offers a vehicle

with hybrid motorization and diesel motorization, while APTS and Hess only offer

hybrid motorization.

Some examples of bi-articulated buses in operation:

In Western Europe, the first example of megabus was put into service in Bordeaux

before the city’s tram network was developed in the nineties. The “Mégabus” was

derived from Renault PR 180, and was 24.38m long. 10 buses of this type were

built in collaboration with Heuliez Bus. These buses’ theoretical capacity was of

206 passengers, for a cost of approximately 412 000 € (in Francs, at the end of the

nineties).

Figure 2 : Bordeaux’s megabus (France)


For its high performance bus project « METTIS », the city of Metz has recently

purchased 27 Exquicity vehicles manufactured by Van Hool. Characteristics of the

vehicles are the following:

- Capacity of 150 passengers

- 24m length

- Unit price of 855 000 €

Figure 3 : Bi-articulated Exquicity bus, Metz (France)

In some other European cities (Aachen, Bascharage, Canach, Geneva, Hamburg,

Leuven, Utrecht, Zurich), 24m long Van Hool AGG330 vehicles (the

manufacturer’s former model) are in operation. Utrecht is the most significant

example, with 27 buses in operation. They have a capacity of 180 passengers. In

Hamburg, 26 vehicles are in operation.

Figure 4 : Utrecht’s bi-articulated bus



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In Latin America, several Brazilian cities (Sao Paulo, Campinas, Goiania and

Curibita) have chosen bi-articulated buses that have been assembled on Volvo

manufactured under frames (the body work being manufactured by Brazilian

builders Marcopolo and CAIO. These buses can carry up to 270 passengers, but in

poor comfort conditions with such load.

Volvo has produced its own megabus mode, the 7300 BRT, which is being

operated in Mexico City and in Gothenburg (Sweden). This model is no longer

produced by the manufacturer.

The Phileas bus, developed by APTS, also exists as a bi-articulated model. It is

being operated in Eindhoven (Netherlands).

5.3 Operational feedback

Feedback on the operation of such bi-articulated buses shows that their integration

in urban traffic flow is complex, especially as far as gyrations are concerned.

Gyration assessments need to be undertaken with adapted software in order to

conceive an adapted road layout, with sufficient road width.

Stations’ platforms need to be longer than for classic articulated buses, in order to

guarantee step-free passenger access all along the vehicle. However, in Eindhoven,

stations’ platforms’ length for Phileas bi-articulated buses goes down to 20m. Only

the first and second doors open. With such a layout, station approach is difficult

and it is preferable to plan for 26m long platform.

What’s more, the main drawback of the vehicles that were operated in Bordeaux

was the lack of comfort for passengers. The bellows which linked the two back

bodyworks of the vehicles accentuated vibrating effects for passengers located at

the rear of the bus.


6 Optical guidance

6.1 System characteristics

As of today, Siemens Transportation is the only manufacturer able to provide an

optical guidance system to facilitate station approach benefiting from an official

approval for operation. This Optiguide / Optiboard guidance system is based on

image processing and trajectory recognition.

A camera placed behind or above the bus’ windscreen detects vehicle’s position

with regards to a double white dotted line painted on the road. The system doesn’t

require any physical connexion between the road and the vehicle and can be

stopped at any moment. The driver can take control of the bus and go back to

manual driving mode at any time if needed, without inducing a loss of speed for the

vehicle. The system is mainly used for station approach, it hasn’t received official

approval for operation on main road sections.

Siemens has developed two types of technology:

- Optiguide technology, which has been put in operation in Rouen and

Nîmes (France), Bologna (Italy), Castellon (Spain). When approaching

stations, driver’s availability to pay attention to vehicle’s surroundings in

increased. As a matter of fact, when optical guidance mode is activated,

vehicle’s trajectory is determined by Optiguide, while driver only controls

speeding and braking.

- Siemens has recently developed a new version of Optiguide called

Optiboard. This system hasn’t been commercialized yet. When

approaching stations, the driver keeps total control of the vehicle. The

system warns of all contact with the platform and allows to:

o Guide the vehicle on the trajectory of the painted dotted line,

o Supporting the driver through an assisted steering system,

o Supporting the driver thanks to stimuli on the steering wheel

(according to vehicle’s position),

o Informing the driver through vibration of the steering wheel

According to Siemens, Optiboard system doesn’t require official approval in order

to be operated. However, this assertion hasn’t been verified yet, as no operational

feedback has yet been made.



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Figure 5 : Explanatory sketch of optical guidance system

Siemens Transportation almost exclusively works for Irisbus in order to implement

its system on bus rolling stock. As of now, inly Irisbus type buses (Civis, Agora,

Citelis) have been equipped with such optical guidance systems, as well as Cristalis

trolleybus (bus electrically supplied in energy thanks to catenaries) also

manufactured by Irisbus. As a matter of fact, Siemens has worked with Irisbus

within the framework of a 10 year exclusive contract. Siemens however proclaims

that its systems can be implemented on all types of buses.

As it implies some degree of complexity, integration studies need to be undertaken

by the bus manufacturer in order to plan for sufficient space within the vehicle

(near steering system) and to set-up the interface between the bus and the guidance

system.

Figure 6 : Rouen’s Agora bus à Rouen, equipped with Optiguide


6.2 Operational feedback: Rouen (France)

Part of the reason why Rouen’s high performance bus system TEOR attained

performance levels similar to that of a tramway was because local authorities opted

for an optical guidance system.

Thanks to this decision, station approach is optimal for Rouen’s TEOR buses

99.9% of the time. The optical guidance system contributed to the regularity of the

line and its commercial speed of 18km/h.

The optical guidance system however displays some drawbacks:

- A 20m straight alignment needs to be preserved before each station

- Important additional costs (see below)

- As TEOR vehicles aren’t equipped with pallets that allow to fill the gap

between the bus and the platform if necessary, there was no system to

guarantee step-free accessibility to the buses in case of breakdown of

guidance system and deficient station approach.

In order to analyse the guidance system’s reliability, we shall first recall the

chronology of its implementation and of the problems noticed since then:

- In 2002, the optical guidance system was implemented. During that year,

the rate of defect was of 1,37 out of 1000 station approaches.

- The rate of defect then stabilized itself up to 2006 at 0,195 failures for

1000 station approaches.

- In 2007, the rate of defect went back up to 0,425 failure for 1000 station

approaches due to the arrival of new (Citelis) vehicles

The implementation of an optical guidance system requires a running-in period that

lasts a few years. Once adjustments have been made, the rate of defect goes down,

becomes low and stabilized itself. It was of 0,15 for 1000 approaches in Rouen in

2011.

Figure 7 : Evolution of rate of defect for TEOR Buses’ optical guidance system from 2005 to

2011



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6.3 Cost of an optical guidance system As of today, there aren’t enough cases where optical guidance systems have been

deployed for bus networks to allow a consistent feedback on the exact cost of their

operational implementation.

In the case of Rouen, the total cost to equip 38 buses with the system was of 3.1

million euros (more than 80 000€ per vehicle). As a reminder, it was a pioneering

project for the development of such systems. However, Siemens announces that the

cost of the deployment of the system is of 2 to 5% of the cost of a new vehicle. It

can thus be assumed that the real cost lays somewhere between these two

estimates, at around 50 000 € per vehicle.

The cost of a technical study for integration in each station also needs to be added

to this amount, which represents an additional cost of around 110 000 € for a given

line.

A calibration station platform and a testing track to undertake camera adjustments

can be built within the line’s maintenance site. This track would also be usable to

train drivers. The total cost of such a layout would be of 45 000 €. It also possible

avoid building such a facility and to use one of the testing tracks that have already

been built by Siemens in several maintenance sites of various rolling stock

manufacturers or bus operators.

6.3.1 Operation costs

Operational costs related to the infrastructure are the following:

- Regular inspection of roadway in order to detect elements which might

affect guidance system,

- Maintenance of roadway and of the road-markings,

- Control of road banking and ruts in order to maintain optimal accessibility

conditions and to limit defects of guidance system.

The proper functioning of the system requires a thorough and regular control and

maintenance of the roadway. The entity (or entities) in charge of performing these

tasks thus need to be clearly identified, and the level of required maintenance will

have to be precisely specified.

For example, Greater Rouen authorities became in charge of the monthly clean-up

of the dedicated roadway the TEOR. TEOR operations center often contacts

Greater Rouen in order to alert them on the necessity to clean up some parts of the

roadway, notably in autumn when there are a lot of leaves.

Operational costs also need to take into account the need for an additional training

for the drivers and bus maintenance agents, which will be undertaken by Siemens

(2 or 3 days per member of staff). In case of system breakdown, the cost of

renewing the entire on-board system for a given vehicle is of 2 000€. These repairs

can be undertaken within the bus line maintenance site.


6.3.2 Maintenance costs

Operational feedback from Rouen’s TEOR project gives an insight on the most

important maintenance cost items for the system.

The maintenance needs to be undertaken by two specialized technicians working

for the bus network operator. Maintenance is achieved through several operations:

- An inspection car runs on the bus roadway every 3 month in order to

check whether the white dotted lines need to be repainted at station

platform approaching areas. The painted lines located in areas where buses

are mixed with the general traffic are the ones that need more repainting.

- The calibration station platform and testing bus roadway located within

the maintenance is used to verify the gap between the vehicle and the

platform. The following aspects are controlled:

o Vehicle alignment with the platform

o Vehicle height

o Clean-up of encoder

- An automatic test is undertaken each time a vehicle leaves the depot and

maintenance site. In theory, no vehicle can exit the site without an

operational optical guidance system.

Cost Remarks

Guidance system :

Inboard guidance system :

+ steering system

motorization

+ lights control

+ access to vehicles

21 000 €

75 % taken into account

by contract with Siemens,

and 25 % related to

curative maintenance

Roadway maintenance 130 000 €

Traffic lights 355 000 €

Specific to local context

(many traffic lights to

replace)

Road marking maintenance 68 000 €

Stations’ maintenance 83 000 €

Roadway clean-up 52 000 €

Systems 185 000 €

Total 826 000 €

Figure 8 : Annual operational cost of optical guidance system in 2011 (Source: Greater

Rouen)



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The annual cost supplement for a bus line equipped with optical guidance system

with regards to a classic high performance transit bus line is of 826 000€.

6.4 Limits of optical guidance systems

The main advantage of optical guidance systems is to allow buses to perform

optimal station approaches and thus guarantee full accessibility for passengers with

reduced mobility.

When a transport authority chooses to adopt such a systems, it needs to ensure

compliance with security regulations and procedures that are in force. Associated

compliance files and forms thus need to be compiled.

6.5 Alternate option: pallets to fill vehicle – platform gap

With a similar level of reliability and a cost that is insignificant with regards to that

of an optical guidance system, such pallet systems offer an interesting alternative

option to guarantee optimal bus accessibility conditions at station platforms.

Figure 9 : View of a pallet system to guarantee accessibility at station platform (open and

closed) (source: Nantes Busway line, France).


Figure 10 : Pallet system technical characteristics

The system consists in a pull-out electrical pallet which requires a 24,5cm high

platform. A A flexible and removable rubber platform hedge should be integrated

in stations’ design in order to absorb potential shocks.

Figure 11 : Flexible and removable rubber platform hedge (Busway, Nantes, France)

Technical Characteristics

Manufacturer MBB Palfinger

Type Mediramp FVM 850-350

Pallet length 350 mm

Largeur de la rampe 920 mm

Maximum acceptable weight on pallet 350 kg

Time need to deploy and pull back pallet 4 seconds for deployment and 4 seconds to pull back

Vehicle door equipped with pallet Door n°2

Exiting mechanism Sliding pallet (electrically power supplied)

Back-up device Handle to deploy and pull back pallet manually

Safety device

Collision detector (when a force above 150kN is reached,

corresponding to 15kg)



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As with optical guidance, the use of pallet systems integrated within buses,

interfaced with station platforms of adequate height doesn’t induce any loss of

time. For bus lines equipped with station platforms that are lower than 24,5cm,

longer pallets are required, which take a longer time to be deployed. The loss of

time in that case can go up to 1 minute each time the pallets have to be deployed.

In the case of Metz high performance bus project “METTIS”, passenger

accessibility is guaranteed by a pallet system. The pallet can be either deployed

automatically at each stop, or can be deployed on driver’s request, when need

(when there is a passenger with reduced mobility capacities awaiting on station’s

platform or when a passenger inside the bus has pressed a dedicated button).

Figure 12 : Metz’s METTIS Exquicity bus and its pallet (Source: Van-Hool)

6.6 Comparative analysis for bus accessibility

The following table allows for a comparison of the two solutions in terms of:

- Required procedures before system is deployed,

- Purchasing process,

- Rolling stock maintenance,

- Station platform maintenance,

- Operation,

- Costs


Figure 13 : Multicriteria analysis – Pallet vs Optical guidance



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Optical guidance and pallet systems both guarantee station approaches that are

fully in compliance with optimal accessibility conditions for passengers with

reduced mobility capacities, while minimizing loss of time at bus stop.

As of today, Siemens has a monopoly over the optical guidance system, which in

Rouen has proved to be reliable enough. Only Irisbus rolling stock has been

equipped with it so far. The cost of purchase of such a system is of approximately

50 000 € per vehicle. Close attention needs to be paid to maintenance clean-up of

bus roadway.

For a quasi-similar reliability, a cheaper cost, and a similar stopping time at each

station, pallet systems can achieve identic performances. As a matter of fact, the

constraints and risks associated with the deployment of an optical guidance system

seem to overweigh the associated gains, which almost exclusively lay on the

guaranteed efficiency of the station approach.

Opting for an optical guidance system is a significant choice that needs to be

undertaken as soon as possible when designing a high performance bus project, at

the latest during pre-project stage. The choice for the most adapted system can only

be made when the bid for rolling stock acquisition is launched.

In the particular case of Aalborg, a brake in using an optical guidance system

could also be the climatic conditions which could impede bus running many

days during the year.


7 Hybrid motorization

This section presents what the bus manufacturing industry is able to offer in terms

of 18 and 24m long buses equipped with hybrid (electric + diesel) motorization, as

well as alternative solutions to diesel engines.

7.1 Different types of hybrid engines

There are two types of hybrid diesel-electric engines: series hybrid traction, and

parallel hybrid traction.

In both cases, the vehicle is equipped with energy accumulators that work during

deceleration and braking phases, recovering the energy generated by the electric

traction engines. Such a function is today operated by batteries or super-capacity

batteries, according to the technical requirements of the project: the choice of

technology can be determined by the will to have the engine working electrically as

much as possible (in which case normal batteries are preferable, for they offer

energy density), or only when the bus is moving off (in which case super-capacity

batteries are preferable for they are more powerful). This electric energy allows to

ease the efforts of the diesel engine during acceleration phases, by limitating its

rotating speed, and thus its fuel consumption and its noise.

Greater Dijon (France) authorities, who deployed such buses in 2013, is expected

to witness a drop in noise pollution. The noise for buses driving at a 30km/h should

drop from 82 decibels to 72.

In comparison with standard diesel vehicles, the interior design isn’t modified as

batteries are located on the roof.

7.1.1 Series hybrid traction

In the case of series hybrid traction, a diesel engine feeds an in-board generator

which produces electricity. This power is then carried to the electric traction

engines that are interfaced with the bus’ axles. There is no physical connexion

between the diesel engine and the vehicle’s axles, which allows for a fully electric

functioning during dozens of meters, sometimes up to a hundred meters, according

to the energy accumulators that have been chosen by the bus manufacturer.

Series hybrid traction engines are in average less noisy than parallel ones.

The strength of the thermic engine needs to go through the generator and the

electric engine, which implies losses. The efficiency on long distances at constant

speed is thus inferior compared with parallel hybrid traction engines. The main

advantage of such type of motorization relies on its use within a city-centre

context, when there is a lot of slowing down, stopping and moving off again, as it

is possible to collect some of the energy generated by braking to recharge the

electric battery. The privileged inter-station distance for a high performance bus

line with a dedicated roadway is of 400 to 500 meters.



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Figure 14 : Series hybrid traction (source: CEREMA)

7.1.2 Parallel hybrid traction

In the case of parallel hybrid traction, the design of the traction chain is quasi

similar to that of a diesel engine. The only difference is that the electric engine is

connected to the vehicle gear, thus allowing for an electric assistance to the fuel

motorization, notably when the driver demands a lot of power from the vehicle

(moving off and speeding phases). Electric motorization is then just a

complementary source of energy, there is actually no physical connexion between

the electric engine and the engine’s axle, which doesn’t allow for a fully electric

functioning of the bus, even just during a very short distance.

One of the advantages of such a system is that the energy of both the electric and

the diesel engine are combined when the bus is speeding up. Parallel hybrid

motorization system are thus more adapted for suburban and intercity lines.

Figure 15 : Parallel hybrid traction (Source: Cerema)


Among parallel hybrid engines, there are two categories:

- Semi-hybrid engines have an electric engine which offers an energy back-

up for the diesel engine when it demands a lot of energy, but they never

entirely take care of vehicle traction on their own. They provide a power

back-up for acceleration phases, the energy being meanwhile stocked in

batteries.

- They can also provide a regenerating braking.

- The energy needs are less important with regards to an integral hybrid

system, smaller batteries can thus be used

- Integral hybrid engines are different as their electric engine can fully

ensure traction of the vehicle at low speed.

The two engines continually relay one another. While the diesel engine is working,

it recharges the electric engine. During stationary phases, both engines are stopped.

While moving off, it is the electric engine which gets the vehicle going, up to

speeds of 25 to 30 km/h, then the diesel engine takes over. In case of a long

acceleration, they can however work simultaneously. An embarked computer

determines which engine has to take over.

Integral hybrid engines however require heavier equipment, with bigger batteries

which reduce available space within the vehicle. It is however the system which

allows for the most significant fuel savings.

7.2 Scope

More than a mere technical choice, these two technologies respond to specific

needs, even though their usage scope sometimes overlap. As a matter of fact, series

hybrid engines are designed for repeated sequences of speeding and braking, hence

in an urban setting. In addition, by communicating bus line layout plans to the

manufacturer, they can work to optimize the output of the traction chain and thus

increase its performances in terms of fuel savings and noise reduction.

The idea that buses with hybrid diesel – electric engines can be best operated

within an urban perimeter has been reinforced by an additional solution offered by

bus manufacturers on series hybrid engines: the “Stop & Start” option. This option

allow to stop the diesel engine while the vehicle is stopped (notably at bus

stations), and to restart it when the vehicle moves off, or a dozen of meters after

that, according to the technical constraints of the engine and of the road layout.

Hybrid parallel engines can on the other hand bring additional power during speed

up phases as described above, thus limiting the fuel consumption peak. They are

more suited for operation within suburban and inter-city contexts.



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7.3 Vehicles on the market and operational feedback

The majority of bus manufacturers today offer series hybrid diesel/electic

motorization technologies. The main manufacturers whose buses are in operation

in Europe are the following: Hess, Heuliez Bus, Irisbus, MAN, Mercedes, Solaris,

Temsa, Van Hool, VDL, Volvo.

City centres being the predominant areas where buses are operated, bus

manufacturers have opted for the hybrid motorization technology that is most

suited to this kind of context, with inter station distances of approximately 400 to

500 meters for a high performance line with a dedicated roadway for the buses, and

regular and repeated acceleration and braking phases when vehicles are mixed with

the general traffic.

Bi-articulated Hess buses with series hybrid motorization are in operation to

connect Luxemburg city and its airport. Operational feedback shows that this

shuttle type of operation is not the most appropriate for this kind of motorization.

The bus mainly circulates on expressways, with maximal passenger load, with no

intermediate stop, meaning the batteries cannot be recharged. However, the bus

operator still witnessed fuel savings with respects to a normal diesel engine for this

kind of bus (52L/100km vs. 75L/100km).

A hybrid version of Citelis 18m long articulated buses has been announced, but

they are not yet referenced on the manufacturer’s catalogue (Iveco). Fuel savings

of 29 to 39% have been witnessed during tests undertaken in Lyon, bus with 12m

long buses.

In Strasbourg where series hybrid 18m long buses (Urbino 18 type by Solaris) are

operated, fuel savings of 15 to 25% have been witnessed. The most important

savings have taken place for buses operated within the most urban areas, where

speeds remain low and braking phases are numerous. This bus type is also being

tested in Meaux (France).

Heuliez has designed an articulated bus (GX 427 series hybrid traction). The city of

Poitiers (France) has purchased one, and they are also in operation in Toulon

(France), with a fuel savings target of 30%. Greater Dijon (France) has signed a

partnership deal with the manufacturer in 2012, for the purchase of 102 of these

hybrid buses. The deal sets a target level of reliability for the vehicles. 3 000

models of this type are currently in operation across the world.

For Metz’s METTIS high performance bus line in France, 27 bi-articulated 24m

long vehicles with hybrid motorization have been put in operation in 2013. The

vehicles have been designed specifically for the line by Van Hool. The buses can

carry up to 150 passengers at a commercial speed of 20km/h. It is the first ever

project in Europe where bi-articulated hybrid buses have been put in operation.


Figure 16 : Metz’s bi-articulated hybrid bus (Van Hool)

Each experimentation needs to be considered taking into account the context in

which it has been conducted. As a matter of fact, the resulting fuel savings

witnessed are always presented in percentage, which requires a reference

observation point with diesel motorization. Such a reference point can affect the

nature of the results, because the energy generation process is generally not the

same compared with hybrid vehicles, which means their performances cannot

really be compared, which explains the gaps between the fuel consumption savings

witnessed.

7.4 Investment cost

Hybrid motorization technology allows for fuel savings, which should entail

financial gains. But the deployment of such a new technology has a cost, notably

that of the purchase of the vehicle. The cost is caused by the additional technic

dimension of hybrid motorization and the related electronic components. In

opposite to diesel buses for which studies and massive industrialization by

manufacturers has been profitable, allowing for purchasing costs to be relatively

low as of today, hybrid buses show an average additional cost of approximately

150 000 € per vehicle.

The cost of a new articulated hybrid bus is of 500 000 euros (Irisbus Urbino 18

buses have been purchased at a cost of 480 000 €).



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7.5 Operational cost

As far as operational costs are concerned, it has to be noted that the electronic

components of the hybrid traction chain do not require specific maintenance, given

their increasing reliability. A short number of additional maintenance operations

are required (additional filters to be cleaned up, checking the cooling system of

energy accumulators).

However, energy accumulators currently constitute the most expensive operational

cost for a hybrid bus. As a matter of fact their life span depends on the number of

charging/discharging cycles carried out, which cannot be estimated in theory by

manufacturers as of today. A life span of 5 to 8 years is today recognised as a

fairly correct assumption for a hybrid bus, which entails an additional cost of 30 to

50 000 € per vehicle each time they have to be replaced. It has to be noted however

that with progress in electronics and electric technologies, battery energy storage

capacities should allow for greater energy storage in a near future, leading to

increased fuel savings.


8 Trolley bus system As the hybrid engines technology, the trolley buses technology is another

alternative offered to the classical motorization.

Trolley bus systems can cope with transport needs of cities which can be small-

sized, medium-sized as well as large-sized:

- In Italy, the trolley buses run in 15 cities: Bologna, Genoa, Milano,

Napoli, Parma, etc.

- In Switzerland, 14 cities are equipped with such a system. The most

important ones are Basel, Bern, Genève, Lausanne and Zurich.

- In France, only three cities conserved their lines of trolley buses: Limoges,

Lyon and Saint-Etienne.

The strengths of such a system are that it is more comfortable and more efficient

than classical buses, above all for what regards acceleration and behavior in

sections with high slopes. Trolley buses does not create tremor which is

appreciable for passengers. They can start with no difficulty, even facing high

slopes of 12% to 13%.

The system is also environment friendly: it does not pollute; and it is not noisy

since it does not create vibrations.

In terms of weaknesses, the system present the inconvenient of being fed by means

of an overhead electrical line, which makes it less flexible than classical buses and

exposes it more to the hazards of road traffic. More than classical bus, this system

shall be reserved to an operation within a dedicated corridor, as a high capacity

system.

Focusing on high capacity trolley buses, some manufacturers such as Irisbus,

Neoman and Van Hool provide some solutions for bi-articulated buses. Another

manufacturer – Hess – also provides a mega trolley bus with three cars.

Hereunder, we provide a technical description for the Cristalis of Irisbus which is

considered as a sophisticated and high quality vehicle, with a cost higher than a

classical articulated trolley bus.



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Figure 17 : Cristalis trolley bus

General characteristics

Number of cars 2

Length of the vehicle 18 m with low floor

Width of the vehicle 2,50 m

Height of the vehicle 3 m à 3,50 m

Height of floor at the access 0,32 m

Number of doors 3

Number of places (with 4

passengers/m2)

100-105 environ

Technical characteristics

Weight of the vehicle 17-20 tons

Traction Electrical (600 V), the power is received by

mean of poles in contact with an overhead

electrical line (two wires). Some

manufacturers provide also the hybrid

engine option.

Power 190 to 200 kW

Maximum speed 60 to 70 km/h

Particularities Auxiliary engines or batteries are necessary

so that the trolley bus can run with some

autonomy.

Life span of the frame and the cars 20 years

Insertion characteristics The same as for other articulated buses.

Costs

Manufactured in Europe Articulated with 2 cars : about 650.000 €

Cost per place offered ~ 6.200 €

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