Transmission Retarder; Antilock Braking System (Abs); Kneeling System - PREVOST H3-41 Manual

Effectiveness of the engine brake system will
vary according to the transmission range in use.
The engine brake system is more effective in
lower ranges and at higher engine speeds.
Warning
: When descending significant
grades, use service brakes as little as possible.
If engine does not slow coach to a safe speed,
apply service brakes and shift to a lower range.
Let the engine (and engine brake) slow the
coach. Keep brakes cool and ready for
emergency stopping.
Note :
Each time the engine brake system is
in operation, the stoplights automatically
illuminate.

TRANSMISSION RETARDER

A retarder is a device that helps to reduce the
speed of a vehicle. It improves vehicle control,
increases driving safety, and permits more
economical operation. The retarder provides
slowing power when it is most needed, such as
when descending mountain roads, in stop-and-
go traffic and on crowded freeways.
The retarder is provided with a switch on the
dashboard and a lever on the steering column
(refer to "Controls & Instruments" chapter).
Note :
Extended use will raise the transmission
oil temperature.
The retarder helps to reduce speed on grades
without using the vehicle's conventional service
braking system. This virtually eliminates brake
overheating and reduces the risk of a runaway
vehicle. A retarder greatly increases the service
life of brake pads and discs, resulting in reduced
brake maintenance costs.
Note :
Each time the transmission retarder
system is in operation, the stoplights will
automatically illuminate.
Note :
For coaches equipped with the
Antilock Braking System (ABS), as the wheels
start to lock-up on slippery roads, the output
retarder automatically deactivates until the
wheels roll freely.
ANTI-LOCK BRAKING SYSTEM
The purpose of the anti-lock braking system
(ABS) is to maintain vehicle stability and control
during braking and to minimize the stopping
distance in any road condition.
On slippery roads and more generally in
emergency situations, over-braking frequently
induces wheel locking. Wheel locking greatly
increases breaking distance on any road
surface, impedes directional control and causes
severe tire abrasion. An anti-lock braking
system provides maximum braking performance
while maintaining adequate control on slippery
roads.
The basis of ABS is constant monitoring of
wheel parameters during braking. Sensors on
each wheel of axles 1 and 2 constantly measure
wheel speed during braking. This information is
transmitted to a four-channel electronic
processor which senses when any wheel is
about to lock. Modulating valves quickly adjust
brake pressure (up to 5 times per second) to
prevent wheel lock. Each wheel is therefore
controlled according to the available grip.
In this way, the coach is brought to a stop in the
shortest possible time while remaining stable
and under the driver's control.
Caution :
Vehicles following ABS-equipped
coaches may not be able to brake as fast on
slippery roads. Whenever possible, warn other
drivers by depressing the brake pedal lightly
several times before braking.

KNEELING SYSTEM

This system lowers the front end, enabling
passengers to get on and off the coach without
any difficulty. The system operates rapidly;
taking only 5 seconds to lower and 9 seconds to
rise.
Note :
This coach is equipped with an
interlock system which automatically applies the
parking brake when the kneeling system is
activated.
To operate, stop the coach, set the transmission
to neutral(N), then push down the rocker switch
located on the dashboard. (Refer to "Controls &
Instruments" chapter). The parking brake will be
applied automatically and a warning flasher will
indicate that the front of the coach is being
lowered.
To raise the front of the coach to its normal
height, push up the rocker switch. The front end
will rapidly rise up. The system will release the
parking brake and shift the transmission to the
previously selected range.
Caution :
Avoid parking the coach too close
to the sidewalk or to other obstacles which could
damage the coach during kneeling.
4-11
OTHER FEATURES