Putting The Brakes On Accidents

The recent media attention surrounding heavy vehicle accidents across Australia is forcing industry regulators to set their considerable sights on company driven maintenance programs.

According to the NTARC (National Truck Accident Research Centre), 25% of all accidents are caused by speed, 12.1% through fire losses and mechanical failure, with fatigue coming in third at 11.9%. Each of these top three causes are shining a light on contributory brake issues.

With the 2013 major accident report released by the NTARC stating that brake problems can result in tyre fires and explosions, recommendations are being made that brake and tyre maintenance become a priority.

Coupled with the recent woes of one of Australia’s largest transport companies being issued with multiple defect notices for brake, wheel and suspension faults (taking 26 of their 80 strong fleet off the road), the major impact on company earnings and reputations cannot be ignored. Neither can the cause.

WHY TEST BRAKES?

Safety

Put simply, we test brakes to ensure vehicles are safe to use. For drivers, for the general public and for the client’s product that is being transported.

Legislation

While each state has their own regulations in place, it is becoming more of a national focus from a regulatory point of view to frequently test brakes.

Liability

Regular brake testing allows the operator to keep an auditable record of testing. In the event a vehicle is involved in an accident, the risk of legal action can be reduced if accurate testing information is readily available.

Economy

Regular testing can minimise vehicle downtime in the workshop, reduce brake lining and component wear and can assist in decreasing tyre wear, saving businesses time and money.

OH&S Fatigue Management

As part of the National Heavy Vehicle Accreditation Scheme (NHVAS) minimising driver fatigue is a critical component. By regularly testing you can provide a smoother ride for operators, resulting in a positive effect on fatigue management.

THE EQUIPMENT

As with any product, there are multiple types of brake testers available. The three main contenders are Decelerometers, Plate Testers and Roller Testers.

The most common and cost effective piece of test equipment is the Decelerometer. Usually found strapped to the passenger seat of the vehicle being tested, it measures and records the inertial force of the vehicle as it decelerates from a pre-determined speed to a stop. Service brake speed is generally around 30klm/hr with the park or emergency brake speed being 15klm/hr.

There are plenty of different types available on the market, however they all basically work off the same “G Force” principal. The transducer of pendulum is read to determine if the vehicle can develop enough brake force to theoretically stop the vehicle safely within a set range of distance.

Being relatively inexpensive and fairly compact, the Decelerometer allows ease of use in most environments.

You have the option of printed paper tape to provide the results and maintenance is cheap and easy, with annual calibration ensuring the accuracy and legality of your testing. They also spend their time in the vehicle cabin so mud and dirt is not an issue.

What they don’t do is provide information pertaining to individual wheel performance. This type of testing will also not show hidden faults like drag and cracked or warped brake drums or disks, as it doesn’t weight the vehicle. Motion is also a factor, with the vehicle required to be moving for testing to be conducted, so there is potential safety issues due to the possibility of the operator getting distracted.

The second type of testing is called Plate Testing. While similar to a Decelerometer in that it measures the inertial deceleration force of a vehicle being driven at a pre-determined speed, the Plate Tester is installed in a static position on the ground and the vehicle is driven on to it. The brakes are then applied while the wheels being tested are on the skid plates, allowing the reading of sideways movement of the vehicle wheel under braking as well.

You can power a plate tester using an extra low voltage source (12vdc) which means minimal exposure to low or high voltage AC power. Plate testers have fewer moving parts, principally the plate itself. One up on the Decelerometer, these testers provide a more in-depth test allowing weighing of vehicle axle (static).

However, like the Decelerometers, Plate Testers require the vehicle to be in motion to allow for the test to be conducted, making for a greater level of distraction as the operator must concentrate on keeping the vehicle at the correct speed, lining up on the plates and then applying the brakes at the exact moment they hit the plates. This is especially important for long vehicle testing such as road trains or B-Doubles, usually this would require other helpers to work with the operator, which can result in reduced consistency in some test situations.

Rounding up the brake testing posse is Roller Brake Testing. Using this style of testing vehicles are driven onto a set of rollers which are covered in a plastic medium infused with friction material. When tested the wheels are turned by the constant speed of the roller keeping the vehicle static during the test.

Roller Brake Testing measures deceleration by means of torque force produced by the decelerations of the wheel against the rollers. This method produces the most consistent results across all axles. You can test one wheel at a time, review efficiency of service, and test parking and emergency brakes.

Roller Brake Testers can be configured for air pressure testing, ovality (warped or cracked discs/drums), Bind (rolling resistance) and in some makes you can accurately test time lag which can help reduce the likelihood of “jack-knifing”. One of the more impressive services that this style of testing provides is the ability to match prime movers to trailers, maximising vehicle balance and efficiency.

Greater safety is achieved with this style of testing with the single operator system allowing control on some systems direct from the vehicle cab via remote control. There are also a number of options to enhance the system including speedo checking, play detectors, emission testers, headlight aimers and noise meters. These accessories give this unit the added advantage of being able, in some cases, to form the basis of a complete vehicle test lane.

While the Roller Brake Tester sounds like the darling of the three it does have some dirty laundry to air. Due to the powerful drive systems, they generally require 3 phase power to operate and can be very unforgiving to humans if safety precautions are not strictly adhered to. The weight of the mobile units can be inhibitive (weighing in a 1.2t for the brake tester). While installation can also present some challenges, with the in-ground units requiring some civil work to get the job done. 

THE BOTTOM LINE

When it comes to operation, Roller Brake Testers will measure the torque reaction generated by the vehicle brakes against a roller turned by a motor, while the Plate Brake Testers have strain gauges attached to a plate supported on bearings, and measure the forces required to hold the plate, when a vehicle is braked on top of it. Decelerometers are placed in the vehicle and have a pendulum (more recently, airbag type accelerators) that moves when a vehicle is braked, the amount of ‘swing’ on the pendulum is measured to indicate deceleration during braking.

When it comes to safety Roller Brake Testing is a comparatively safe method of testing, the vehicle does not move during the brake test, the rollers ‘act as the road’ and turn under the wheel. With both the Plate Brake Tester and the Decelerometer, testing requires the vehicle to be driven and braked on the plates, usually within the confined space of a vehicle workshop or roadside. This could be a hazard to other road or workshop users.

Roller Brake Testers use the same braking surfaces to test all of the wheels, on all of the vehicles; ensuring accurate comparative tests. Plate Brake Testers use the same braking surfaces for all of the wheels, on all of the vehicles, while the Decelerometer tests on road so the braking surface can vary from very good to very bad pending conditions.

While Roller Brake Testers test all vehicles at a consistent test speed, both the Decelerometer and Plate Brake Testers tend to test at variable test speeds; depending on how the vehicle is driven.

Roller Brake Testers can test the entire range of every brake fitted to the vehicle, from zero to full braking, or wheel lock, consistently and repeatedly, without the influence of momentum or weight transfer. The Plate Brake Testers and Decelerometers cannot test the entire range of a vehicles brake successfully.

Decelerometers cannot test individual axles, Plate Brake Testers can compare the balance of brakes across individual axles, while Roller Brake Testers are able to consistently and repeatedly compare the balance of the brakes across individual axles.

Roller Brake Testers use external power for the brakes to work against, typically electric motors, therefore the time taken for the test can be controlled by the operator. On average brake tests applications last approximately 20-40 seconds. Plate brake testers and Decelerometers use the vehicles inertia to provide the power to conduct the brake test, results have to be achieved in the time it takes for the vehicle to stop, brake testing results are typically taken in a couple of seconds.

Roller Brake Testers are able to achieve consistent and repeatable results for brake tests for individual wheels to full brake effort or wheel lock up, while Plate brake testers and Decelerometers normally do not brake to full capacity, as this would be too dangerous. The brakes are tested to try to exceed a pre-defined deceleration and if this figure is exceeded then the brakes are deemed to be ‘good enough’.

The Roller Brake testers are compact but require sufficient room each side of the brake tester for the vehicle. Plate Brake Testers are the most space greedy, with a large area required for the plates and a suitable amount of room required for acceleration and deceleration including a safe overrun area. The Decelerometer is the most space friendly, with no installation required for the vehicle mounted unit.

To give meaningful loading results with the all three of the testers, the vehicle needs to be loaded to more than 60% of its carrying capacity, or in the case of the Rolling Brake Tester, a simulated load applied.

THE FACTS

Driver fatigue, mechanical failure and speed dominate as the main causes of heavy vehicle accidents, costing lives and billions of dollars across Australia every year. Safety and maintenance is being brought into focus through critical media attention which will send a ripple out across the entire industry.

It is safe to say that with the introduction of the National Heavy Vehicle Regulator in February, a greater focus on a national standard for vehicle maintenance and inspection cannot be far behind.  Will you be ready?