Concern About Use Of Wooden-Bodied Buses

Press, Volume CII, Issue 30144, 30 May 1963, Page 6

Concern About Use Of Wooden-Bodied Buses

(New Zealand Press Association)

WELLINGTON, May 29.

The question of using old model, wooden-bodied passenger service vehicles for contract trips should be examined by the authorities, said the report of the committee of inquiry into the fatal North Auckland bus accident on February 7 in which 15 persons lost their lives. « - .

The report, issued by the Minister of. Transport (Mr McAlpine) today said it was believed the high incidence of fatalities was caused by the disintegration of the body of the vehicle before it came to rest.

It was recognised that vehicles having meta.l- - bodies, sheathed with metal, were capable- of withstanding considerable impact damage and were likely to remain reasonably intact even after accidents similar to the one under review. Had the vehicle been fitted with an all-metal body, it was reasonable to assume the death rate would have been lower.

Although there was no evidence to suggest that the vehicle failed to comply with the requirements of the regulations concerning its construction and use, its age. general mechanical condition and type of bodywork, although adequate for normal timetable service and school transport, left considerable doubt as to its suitability for use on ■ longdistance contract work, traversing strange roads under more arduous conditions of driving and operation than was normal, the report said. Consideration should, therefore, be given to limiting the use of vehciles of this type on long-idstance contract work.

The report said the cause of the accident was the failure of the service braking system soon after the bus began going down the Brynderwyn hill, i. There was failure of a rubber seal behind one of the pistons in the right-hand rear brake cylinder, thus allowing the brake fluid to escape. A lack of correct lubrication on the anchor pin holding the leading brake shoe caused the shoe to. fail to return to its normal position clear of the brake drum. Wear to Lining Friction between the shoe and the drum caused accelerated wear to the lining until only a small portion remained on the shoe and then considerable wear of the metal portion of the shoe which was in contact with the brake drum.

This wear, together with excessive wear in the brake drum itself, allowed the piston operating the shoe to emerge from the brake cylinder to an extent that it became tilted within the cylinder. The rubber cap which acted as a seal for the hydraulic brake fluid became damaged by being forced into the space below the tilted piston and finally burst, allowing the hydraulic fluid to escape and so rendering the service braking system inoperative. “It is improbable that the driver would at any time have had any warning from the actual operation of the vehicle that anything was wrong with the braking system.” said the report. “The bus was loaded to near capacity and just before the accident there was confusion and movement among the passengers. It is not considered that this had any bearing or in any way contributed to the accident. “The failure of the braking system must have been sudden and instantaneous and had it occurred anywhere but on the downward side of a steep hill it is improbable that there would have been any serious consequences,” said the report. The foot brakes had been relined in October last and it appeared that the mechanic who checked pie rear brakes was unfamiliar with the particular type of brake in that he assumed the method of adjusting the rear brake shoes for clearance by turning a small “snail” cam was the same as for the front wheel brake shoe. In fact, the adjustment procedure was different. It was recommended that

operators of passenger service vehicles be required to keep for each one some form of record which would show the nature of repairs, their date, the mileage ait the time and the name of the person making the repairs. This was intended only for adjustments, renewals or repairs to braking and steering equipment. The record should be attached to the vehicle and transferred to a new owner. Such a record would be useful at the time of a warrant of fitness test.

Type of Handbrake The type of handbrake on the'accident vehicle, a “Trustop,” which acted on a disc on the cardan drive shaft, while no doubt effective as a parking or holding brake, was a very poor substitute in the event of a failure in the normal service brake.

Acceptance of a cardan shaft brake as complying with the requirements of a parking brake should be examined with a view to prohibiting the installation of this type of brake on passenger service vehicles which were to be built, except where an approved type of tandem or dual master cylinder, operating the front brakes separately from the rear ones, was fitted. The evidence showed application of the handbrake by the driver soon after the vehicle became out of control did check speed momentarily. The type of handbrake, even in first-class condition, would not have been able to reduce the speed of the vehicle to a level when it was fully under control. Had some other type of handbrake been fitted, such as one which acted mechanically on both rear wheels or was effective on one pair of wheels, reasonable control of speed would have resulted.

Although the passenger load was not a contributing factor to the accident, the fact that the bus was carrying standing as well as seated passengers drew attention to the advisability or otherwise of passenger service vehicles engaged in. the carriage of contract parties being permitted to carry

standing passengers on long journeys. Recommending that the fegulationii be amended, the report said it was undesirable for buses undertaking long journeys sometimes over comparatively unfamiliar routes and frequently at night to carry standing passengers. The committee realised that school buses were often used to carry contract parties and in the operation' of such, buses in daylight over regular known routes and comparatively short distances the carriage of standing passengers could be reasonably permitted, the report said.