that we would face certain start-up problems when we commenced high volume production. As these problems surfaced, they were immediately resolved.

Berg is presently marketing its system strictly to trailer manufacturers and, accordingly, trailers equipped with the Berg systems must, of necessity, be used with tractors having a variety of pre-121 and 121 systems. There are in excess of 100,000 Berg axle systems on the road today. Conservatively, even assuming two axles per trailer, there are a minimum of 50,000 Berg-equipped vehicles on the road. Had there been any compatability problems, we would be unable to market our product. We are unaware of any compatability problems.

Berg has had its share of manufacturing start-up problems. One of these problems necessitated a safety-related defect campaign in December of 1976. To our knowledge, there have been no accidents as a result of the use of our system. Whenever required, Berg has responded immediately by providing qualified personnel and an adequate supply of parts to the field. In almost all cases where our customers have advised us of isolated problems, a Berg technician was at the customer's place of business, wherever located, within twenty-four hours. Berg has published service and maintenance manuals and has held hundreds of training sessions at fleet maintenance shops, at OE branches and at independent dealer outlets. These

practical sessions have produced a greater field understanding and have improved the self-sufficiency of fleet maintenance operations. We are convinced that this continuous educational process will result in further reductions of down-time and warranty claims.

Berg's experience to date indicates that more than twothirds of the anti-lock components returned to its factories are, in fact, good and acceptable. At the NHTSA request, we reported our field warranty experience, which was less than 1% of units in the field. We can unequivocally say that the percentage of field service calls and material returns have continued to decrease steadily. Quantitative information was

submitted to NHTSA in September of this year.

We have completed an arduous learning program. As

indicated by our experience in the field, we are confident that the Berg anti-lock is meeting and will continue to meet the

need for safer braking.

We have commenced our second generation of anti-lock systems, which will meet the standard as well as provide a lower-cost, easier-maintenance system and more efficient braking.

Earlier, I referred to the problems encountered when the anti-lock system progressed from pilot to full production. In my opinion the quality of current installations of anti-lock systems is superior to those installed at the inception of the

program, and that this evolution could not have been attained any other way than by actual over-the-road experience.

We are convinced that the FMVSS-121 program accomplishes the anticipated objectives.

Senator EAGLETON. Mr. Hildebrandt?

TESTIMONY OF RICHARD HILDEBRANDT, GROUP DIRECTOR OF ENGINEERING, HEAVY VEHICLE SYSTEMS GROUP, BENDIX

CORP.

Mr. HILDEBRANDT. My name is Dick Hildebrandt. I am the group director of engineering of the heavy vehicle systems group of the Bendix Corp. in Elyria, Ohio.

I am pleased to have this opportunity to participate here today. Briefly, by way of introduction, Bendix is a major supplier of air brake system components to the commercial vehicle industry, and the only supplier who manufactures all the system components from the compressor through the foundation brakes, including antilock.

The Federal Motor Vehicle Safety Standard 121-FMVSS 121-has provided for substantial improvement in commercial vehicle braking performance and controllability. Service and emergency brake stopping distances are shorter, all vehicles are now equipped with parking brakes, emergency systems are of the dual circuit concept and vehicle stability, while braking is assured through antilock wheel control systems.

Prior to FMVSS 121, most vehicles were designed and manufactured to conform to Bureau of Motor Carrier Safety and California requirements, Society of Automotive Engineers-SAE-recommended practice and other agency requirements such as the National Education Association for schoolbuses. Conformance to these requirements resulted in good braking performance.

However, strict compliance to the most comprehensive and demanding requirement as promulgated by the SAE were voluntary and not regulated by fines and penalties for noncompliance. Generally, these requirements were performance acceptance standards and capable of compliance under average vehicle conditions of wheel base, center of gravity location, and load and road conditions.

I turn now to the service system.

The major advances as required by FMVSS 121 are in requiring laden and unladen performance to be the same on dry roads, and adding low speed wet road performance and the requirement of not permitting wheel lockup above 10 mi/h. As shown in the attached figure 1, the laden high speed dry surface stopping distance has reduced by 19 percent from pre-FMVSS 121 vehicle levels, while lowspeed performance is essentially the same. The wet road and no lockup requirement necessitates antilock braking systems.

A reliable and functioning antilock system is a significant contribution to commercial vehicle highway safety. Maintaining both direction stability and steering control are impossible with locked wheels. Locked wheels have no lateral force component necessary for reaction to the vehicle forces, resulting from yaw conditions.1

Antilock system technology was relatively unsophisticated in light of the overall technology available in 1966 and even less sophisticated in light of today's technology. Both the pneumatic and electronics were well within the state-of-the-art.

1 See fig. 2 of statement on p. 485.

During the implementation phase of FMVSS 121, several antilock system problems occurred, including wiring and radio frequency interference problems. In our judgment, these problems were the result of two factors:

One, application of the current technology to a new environment; specifically, electronics to the over-the-road truck environment; and, Two, normal startup problems that result from the legal requirement to completely change a braking system that had been developed in an evolutionary manner over many years.

It should also be noted that when an antilock system fails, normal vehicle braking is still available.

All antilock system suppliers have supported this government regulation and have, to our knowledge, corrected their problems. They have also engineered more cost effective systems.

Other gains in the service brake system are in air reservoir capacities. Tractor and truck capacities have increased by 50 percent, trailers by 100 percent, while buses remain the same."

The brake horsepower requirements are also slightly increased over the SAE recommended practice.3 Pneumatic timing as shown in figure 5 is also comparable to SAE requirements with the exception of release which shows a 27 percent improvement in response.

I turn now to the emergency system.

The dual circuit requirement of FMVSS 121 is to be commended. Now we have a mode of emergency operation that is currently required of all passenger cars and also exists on commercial vehicles equipped with dual hydraulic brake system.

There is no better way to perform emergency braking than to do what is required for normal braking. That is, push on the brake pedal while keeping both hands on the steering wheel while bringing the vehicle to a controlled stop.

The performance in the partial system mode is comparable to SAE at low speed, but 20 percent shorter at high speeds."

There is, however, one deficiency in the trailer emergency system as required by FMVSS 121. Specifically, the trailer emergency effectiveness has been reduced by approximately 50 percent from the pre-121 level. This is the result of using the trailer spring brakes as opposed to the full pneumatic system available through the relay emergency system on pre-121 vehicles.

In this regard there is a Bendix petition and others at the National Highway Safety Traffic Administration for reconsideration of this

concern.

I turn now to the parking system.

Parking requirements are also improved over pre-121. Specifically, a 20 percent grade holding in powered vehicles has been realized, while on towed vehicles a grade holding capability is required for the first time. Possibly this across-the-board trailer requirement is aggressive, and optional considerations should be given.

I turn now to Bendix's involvement in FMVSS 121.

2 See fig. 3 of statement on p. 486. 3 See fig. 4 of statement on p. 487. See fig. 6 of statement on p. 489. See p. 488.

See fig. 7 of statement on p. 490.