Public Service Vehicle (PSV) Workshop

Education Handout (V3 10/01/10)

The UKRO authorises the use of the educational information contained within this document,

however reference must be given to UKRO with the use of the UKRO logo

www.ukro.org

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1. Introduction

With the increase in road use and the increasing population within the UK a rise inthe number of coaches and public service vehicles has been seen.

For the operational firefighter incident complexities involving such vehicles rangefrom entrapments, firefighting, stability, constructions and access.

This document aims to give firefighters an overview of modern PSV constructionsand provide information on stability, glass, fuel and access issues.

The information contained within this handout as part of the workshop is a smallamount of the information which is being made available through the UKRO and itspartnership organisations. Should you wish to receive further information pleasecontact Dick Dawson who is part of the UKRO Education Committee(ddawson@ukro.org)

2. New Technologies and Construction

Most modern buses (2002 onwards) are of modular construction and are not builtupon a full traditional chassis, normally a front/ rear sub frame design.

Glass panels form part of the vehicle structure and may be bonded, where as frontand rear windscreens can still be held in by the more traditional rubber seal, whichcan facilitate easy access if necessary.

Typical examples of these vehicles are:

• Wrights Gemini (body) on Volvo chassis• Dennis Alexander (body) on Dennis chassis

The body frame and floor frame is built from square steel tube section and pressedpanelling/ sections, body panels are made from galvanised sheet steel or alumini-um (approx 1.0mm) with fibre glass reinforced plastic (FRP) mouldings.

Often the front and rear vehicle facings are of FRP construction.

Compromising any pillars or part of the panels will be detrimental to the structuralintegrity and should be avoided wherever possible, unless suitable structural stabil-isation is employed.

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Square Construction of PSV Vehicle

As with traditional extrication standards when examination of a vehicle structuretakes place, it is necessary for a ‘peel and reveal’ strategy. As the pictures belowshow, the internal panels within PSV are lined with various types of insulationmaterials and covered with FRP panelling

A useful guide for firefighters wishing to stabilise and lift PSV’s in particular doubledecker buses, we have the following approximate weights and dimensions:

• total height: 4.39m• total weight: 12,500kg• front axle weight: 3,500kg• rear axle weight: 9,000kg

Engine stop and power isolation

The engine can bestopped via anemergency stop buttonlocated at the rearunder a lift up paneland will be clearlylabelled. Operation ofthis button will stopthe engine but willleave the ancillarypower on.

There is an isolation switch located in the driver’scabin which is clearly marked and housed underan orange safety cover (other manufacturers willemploy a similar system).

This switch will stop the engine and turn off allancillary power.

When the engine is stopped, air will leavethe system and the spring brake will beactivated. The vehicle will also lower as theair leaves the air suspension system.

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Driver’s emergencyisolation switch

Emergency Engine Stop

The batteries can be isolated via a remote switch (these will vary depending onmanufacturer).

The electrical system is 24 volts.

Fuel Tank Locations

Located on the front axle either on the centre line inboard or behind an outer bodypanel, plastic construction on more modern vehicles.

Capacity 180 litres (city bus) up to 1,000 litres (coach)

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Batteries and isolation switch

Battery Tray in the Extended

Stabilisation Considerations

It is important to consider the construction of the vehicle when determiningsuitable jacking/lift points and areas for blocking for stabilisation.

The modern buses are not built on a full traditional chassis, and consist of a frontand rear sub frame.

When jacking/lifting, it is possible that the chassis will distort causing stressedglass panels to break. This ismore likely to occur indouble-decker vehicle.

Crews must be aware of thepotential for glass fragmentsto fall from both the upperand lower decks.

PPE must be worn andprotection provided tocasualties.

The sub-frames should beused as jacking/lift pointswhenever possible tominimise the risk of theabove

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Modern vehicle, low chassis

Depending on vehicle manufacturer there may be markings on the body to indicatethe position of lifting points. Such points are substantial and can be utilised forstabilisation and lifting.

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Older vehicle, traditional chassis

Drivers Seat

There are two types of seat in current use in PSV vehicles, the mechanical and thepneumatic (air seat) which by far the most common. Both use a cantilever typeframework with either a mechanical spring/ damper or a pneumatic air bag as thesuspension component.

The pneumatic seat is supplied via the vehicles auxiliary air supply circuit at apressure up to10 bar.

In a collision scenario the seats movement needs to be managed by inserting ablock/ wedge into the lower framework, lowering the seat under control using thecontrols, and then disconnecting the seats air supply.

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Cantilever / scissor frame

Air bag / spring

Damper Unit

Electric Seat AdjustmentControls (see next pagefor more information)

Drivers Seat Controls

A correct understanding of the controls on PSV drivers seats can ensure that theactions taken by firefighters result in anticipated results. Additionally, thisunderstanding will allow a greater number of options for firefighters planning theirrescue.

The Damper Control enables the driver to adjust the level of damping available onthe seat. This reduces the amount of rebound from the air seat.

The Swab Tilt Control allows the angle of the seat base to be adjusted to suit thedriver.

The control of primary importance is the Air Dump Control button. Although shownhere in red, this is not always the case. This can be used to remove the air fromthe airbag under the seat and will allow the seat to drop down. This would be usedin conjunction with a wedge to stabilise the drivers seat. A prefered method whichprovides additional progressive control when lowering the seat, is the use of theseat height adjustment control button.

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Damper Control Back InclineControl

Seat HeightAdjustment

Control

Swab TiltControl

Air DumpControl

Brakes

Vehicles are equipped with a full airbraking system, which is supplied withcompressed air from an engine mountedcompressor and stored in steel storagetanks mounted on the chassis. Thehandbrake is mechanical (spring brake)with a manual wind off.

When the engine is not running, air willleave the system and the spring brakewill operate. It will not be possible towinch a bus with the spring brakeapplied, therefore early consideration shouldbe given to requesting specialistassistance.

In exceptional circumstances it may benecessary to move the vehicle after theengine has been switched off and thespring brake has been applied. Thespring brake can be manually wound offutilising a 24mm spanner.

On some vehicles, access to the springbrake can be gained via an interior panelover the rear wheel arch. Spring brakesare only fitted to the rear.

When activated, the parking brake lever(Handbrake) will lock in the ON position.To release the parking brakes, therelease collar needs to be lifted beforethe lever can be operated. If the parkingbrake lever is not locked in position theparking brake should be considered off.

In the event of a PSV rescue or collisionat the earliest stages the vehiclesparking brake should be considered.

Repeated operation of the drivers foot valve or manual draining of the vehicles airtanks will bring on the parking brake automatically if access to the parking brakelever is restricted.

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Access Panel to Spring Brake

Release Collar

Spring brake chamber(handbrake shown in wound off position)

Suspension

The suspension is provided by means of air bags front and rear, with additionalsemi-leaf springs at the rear.

The system is supplied as in the air brakesystem from a storage tank, it is controlledelectronically via a chassis mounted levellingvalve which constantly adjusts suspension rideheight according to passenger load.

The driver has dashboard controls to facilitate“Kneeling”, where the bus’s ride height can belowered to assist elderly and disabledpassengers, the vehicle may also have adesignated lifting step for wheel chaircustomers.

The driver may well also have a control to raisethe vehicle on its suspension, this may proveuseful when attending an incident where aperson has been run over etc.

Note: The vehicle must be stabilisedbefore firefighters attempt a rescueunder an air suspended body,should an air bag fail the vehiclesride height will drop withoutwarning.

Suspension Air Bag

Lifting Step

Drivers main control panel,including air suspension.

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Suspension Guidelines

Remove ignition key and operate the drivers emergency isolation switch prior tooperations.

Failure to do so may result in the air suspension system compensating formovements caused by air leaks or jacking and/or stabilizing measures.

When the engine is not running, air pressure will reduce within the airbags causingthe bus to lower.

Attention to the possibility of the vehicle lowering must be given whilst correctstabilisation procedures are followed.

An older standard bus with no kneeling mechanism will have much greater groundclearance of approximately 350mm.

Use sub frame for jacking points

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Emergency Exits

Emergency exits are located atthe off side rear, and the rearwindow of the upper deck. Theupper deck emergency window ishinged at the top and opensupwards; it should be noted thatthere is no stay to maintain thewindow in the open position.

In some circumstances, the emergency exitswill not be available or deemed inadequate tothe situation; therefore, consideration will begiven to the removal of glass panels for spacecreation.

In the main glazing is toughened across thesides and rear, and usually bonded in on newcoach’s/ busses.

The front windscreen tends to be held in by a traditional rubber seal.

Also a point of interest is the drivers side sliding window is also rubber sealed, thusmaking glass removal quicker and cleaner to the experienced firefighter.

Glass now forms part of the overall strengthening of the vehicle body, andstabilisation needs to be considered if especially side glass is removed.

Rear Emergency Exit

Side Emergency Exit

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