CLOSER CHECK ON BUS BRAKES RECOMMENDED

Press, Volume CV, Issue 30961, 18 January 1966, Page 3

CLOSER CHECK ON BUS BRAKES RECOMMENDED

Committee’s Report On Rata Tragedy WELLINGTON, January 17. Two recommendations for the safety 7 of buses have been made by the committee appointed to inquire into the Rata bus accident. Six of the 29 women passengers on the bus died after the crash on July 16.

The committee’s report was released today by the Minister of Transport (Mr McAlpine).

It recommends that all passenger service vehicles be equipped with cardan shaft hand brakes and with tandem master cylinders so that front or rear brake systems can be operated independently should either fail.

The second recommendation was that the repairs and maintenance records bus operators are required to keep be on a standardised form issued by the Transport Department in cases where a satisfactory system is not already in use.

Brake Failure The committee said the cause of the accident was the failure of the service, or footbraking system, which may have begun just before the accident, or during the descent of Pollgreen hill, when the driver was making strenuous efforts to check the speed of the vehicle. “The service brakin.- system became inoperative because of an extensive fracture of the outer cast-iron band on the off-side rear brake drum, coupled with multiple fractures in the drum housing, particularly at its junction with the cast-iron band. “When the foot-brake was applied, the fracture in the cast-iron brake drum band opened and allowed a piston in the brake shoe actuating assembly to move out beyond its normal limit, to tilt, and cut off a segment of the rubber hydraulic oil sealing cup. Loss Of Fluid “The cut in the hydraulic oil sealing cup destroyed its efficiency as a seal, and each movement of the foot-brake pedal by the driver resulted in a loss of hydraulic braking fluid until finally the front and rear wheel brakes were ineffective,” the committee said. But there were other contributing factors. “Efforts made by the driver just prior to, and during the initial period when the vehicle was descending the hill to control the speed of the bus by changing down from top to third gear, ana to move the two-speed axle from high to the low position, were unsuccessful, as were h 1 subsequent actions in trying to engage other gears. “This meant that the (axle) equipment was not meshed either in the high or low position and was in fact in neutral, so that the bus was free-

wheeling down the grade and no use could be made of the hand-brake, or of the retardation offered by the engine to control the speed,” the committee said.

“No Answer” The committee could find “no conclusive or satisfactory answer to the question of why the driver failed to accomplish a change down in gears. “Evidence was given that on a trip from National Park to Levin on July 11, 1965, another driver of the same bus experienced difficulty with the operation of the (axle) equipment.

“On the other hand, an exhaustive examination of this equipment made after the accideint by the Transport Department senior vehicle inspector at Palmerston North failed to reveal any defects which would cause difficulty in changing the two-speed rear axle assembly from high to low ratio, and vice versa. “A possible explanation of the failure to engage the gears and the (axle) equipment, was that the driver left until too late his efforts to accomplish this, and because of the speed of the bus he was unable to match this with the appropriate speed of the engine to permit the gears to mesh.”

Bus Complied The committee said that at the start of the journey—for which the bus was chartered to take members of the Horowhenua Floral Art and Garden Club to a floral display at Hunterville—the bus complied with all statutory requirements applicable to a vehicle of its type. With its first recommendation, the committee said that until it became obligatory, motor vehicle inspectors of the Transport Department should be instructed when making six-monthly inspections to examine the brake drums on all passenger service vehicles more than 10 years old and on other passenger service vehicles as considered necessary, having regard to the age and condition of the vehicles.

“The committee regards this recommendation as one

which requires urgent attention.”

The committee said that the Committee of Inquiry into the Brynderwyn bus disaster in 1963 had recommended, and this had been adopted, that all new passenger service vehicles fitted with cardan shaft brakes and having a hydraulically operated service braking system be equipped with ..dual or tandem hydraulic master cylinders from April, 1965. “This provision takes care of the future, but it is felt that this requirement should now apply to all passenger service vehicles having a cardan shaft brake and a single hydraulic master cylinder. “Attention is also drawn to the danger of exceeding the manufacturers recommendation in regard to grinding out brake drums of passenger service vehicles, especially when a powerful booster unit is employed to increase braking effort. “It is believed, in the case of the accident vehicle, that a combination of these two factors led to the failure of the right rear brake drum.”

Log Produced On repairs and maintenance records, the committee said that a log book in respect of another vehicle had been produced at the hearing. “But because of the paucity of information it contained and the difficulty in ascertaining what the information referred to, it is felt that if this information is to be of any value to motor-vehicle inspectors when carrying out vehicle inspections, it should be recorded in a clearer and fuller manner.

“For this reason, it is recommended that record cards be approved and issued to vehicle owners by the Transport Department.” Under the heading “General Comment,” the committee said that vulnerability of woodenframed bus bodies in an acci-

dent was discussed at the hearing and figures of the number and ages of such vehicles were supplied by the Transport Department’s "chief automotive engineer.

Wooden Bodies “The committee is aware that all bus bodies built after April 1, 1966, are required to be constructed in metal, and it is of the opinion that although the construction and condition of the body on the accident bus in no way caused the accident, nevertheless, it cannot escape the conclusion that it was a contributory factor to the high death toll. “In view of the large number of wooden-framed bus bodies still in active service—--1082 or 22.9 per cent of all vehicles—and of the inability of the local body-building firms both to supply bodies for increased services as well as replacements of old wooden-framed and earlier metal-framed vehicles over a short period, the committee has no firm recommendation to make in this regard, other than to draw attention to the vulnerability of wooden-

framed vehicles when involved in an accident.” The committee consisted of Mr F. F. Reid, of Christchurch (chairman) and Mr J. W. F. Welch, of Auckland.